114-993: Ureaplasma is a genus of bacteria belonging to the family Mycoplasmataceae . As the name implies, Ureaplasma is urease positive. The currently accepted taxonomy is based on the List of Prokaryotic names with Standing in Nomenclature (LPSN) and National Center for Biotechnology Information (NCBI) U. miroungigenitalium Volokhov et al. 2020 U. zalophigenitalium Volokhov et al. 2020 U. gallorale Koshimizu et al. 1987 U. parvum Robertson et al. 2002 U. urealyticum Shepard et al. 1974 U. diversum Howard & Gourlay 1982 U. canigenitalium Harasawa et al. 1993 U. cati Harasawa et al. 1990 U. felinum Harasawa et al. 1990 " Ca. U. intestinipullorum" Gilroy et al. 2021 U. canigenitalium U. diversum U. parvum U. urealyticum This bacteria -related article
228-471: A monotherapy , the likelihood of remission was 22% higher if probiotics were used in combination with 5-aminosalicylic acid therapy. Whereas in people who are already in remission, it is unclear whether probiotics help to prevent future relapse, either as a monotherapy or combination therapy . Probiotics are under study for their potential to affect irritable bowel syndrome , although uncertainty remains around which type of probiotic works best, and around
342-543: A potential difference analogous to a battery. The general lack of internal membranes in bacteria means these reactions, such as electron transport , occur across the cell membrane between the cytoplasm and the outside of the cell or periplasm . However, in many photosynthetic bacteria, the plasma membrane is highly folded and fills most of the cell with layers of light-gathering membrane. These light-gathering complexes may even form lipid-enclosed structures called chlorosomes in green sulfur bacteria . Bacteria do not have
456-404: A terminal electron acceptor in a redox reaction . Chemotrophs are further divided by the types of compounds they use to transfer electrons. Bacteria that derive electrons from inorganic compounds such as hydrogen, carbon monoxide , or ammonia are called lithotrophs , while those that use organic compounds are called organotrophs . Still, more specifically, aerobic organisms use oxygen as
570-744: A bacterial strain. However, liquid growth media are used when the measurement of growth or large volumes of cells are required. Growth in stirred liquid media occurs as an even cell suspension, making the cultures easy to divide and transfer, although isolating single bacteria from liquid media is difficult. The use of selective media (media with specific nutrients added or deficient, or with antibiotics added) can help identify specific organisms. Most laboratory techniques for growing bacteria use high levels of nutrients to produce large amounts of cells cheaply and quickly. However, in natural environments, nutrients are limited, meaning that bacteria cannot continue to reproduce indefinitely. This nutrient limitation has led
684-421: A cause-and-effect relationship between consumption of probiotic products and any health benefit. There is no scientific basis for extrapolating an effect from a tested strain to an untested strain. Improved health through gut flora modulation appears to be directly related to long-term dietary changes. Claims that some lactobacilli may contribute to weight gain in some humans remain controversial. There
798-424: A disorganised slime layer of extracellular polymeric substances to a highly structured capsule . These structures can protect cells from engulfment by eukaryotic cells such as macrophages (part of the human immune system ). They can also act as antigens and be involved in cell recognition, as well as aiding attachment to surfaces and the formation of biofilms. The assembly of these extracellular structures
912-413: A few micrometres in thickness to up to half a metre in depth, and may contain multiple species of bacteria, protists and archaea. Bacteria living in biofilms display a complex arrangement of cells and extracellular components, forming secondary structures, such as microcolonies , through which there are networks of channels to enable better diffusion of nutrients. In natural environments, such as soil or
1026-415: A few species are visible to the unaided eye—for example, Thiomargarita namibiensis is up to half a millimetre long, Epulopiscium fishelsoni reaches 0.7 mm, and Thiomargarita magnifica can reach even 2 cm in length, which is 50 times larger than other known bacteria. Among the smallest bacteria are members of the genus Mycoplasma , which measure only 0.3 micrometres, as small as
1140-426: A fixed size and then reproduce through binary fission , a form of asexual reproduction . Under optimal conditions, bacteria can grow and divide extremely rapidly, and some bacterial populations can double as quickly as every 17 minutes. In cell division, two identical clone daughter cells are produced. Some bacteria, while still reproducing asexually, form more complex reproductive structures that help disperse
1254-400: A growing problem. Bacteria are important in sewage treatment and the breakdown of oil spills , the production of cheese and yogurt through fermentation , the recovery of gold, palladium , copper and other metals in the mining sector ( biomining , bioleaching ), as well as in biotechnology , and the manufacture of antibiotics and other chemicals. Once regarded as plants constituting
SECTION 10
#17328688657011368-525: A health benefit is provided by the product when no scientific proof exists to demonstrate that health effect. In the United States, the Food and Drug Administration (FDA) and Federal Trade Commission (FTC) have issued warning letters and imposed punishment on various manufacturers of probiotic products whose labels claim to treat a disease or condition. Food product labeling requires language approved by
1482-607: A health claim that is not measurable. A group of scientific experts assembled in Canada in October 2013 to discuss the scope and appropriate use of the term "probiotic", adjusting the definition to be "live microorganisms that, when administered in adequate amounts, confer a health benefit on the host." Live probiotic cultures are part of fermented dairy products , other fermented foods, and probiotic-fortified foods. Lactic acid bacteria (LABs), which are food fermenting bacteria, have
1596-408: A membrane-bound nucleus, and their genetic material is typically a single circular bacterial chromosome of DNA located in the cytoplasm in an irregularly shaped body called the nucleoid . The nucleoid contains the chromosome with its associated proteins and RNA . Like all other organisms , bacteria contain ribosomes for the production of proteins, but the structure of the bacterial ribosome
1710-528: A particular organism or group of organisms ( syntrophy ). Bacterial growth follows four phases. When a population of bacteria first enter a high-nutrient environment that allows growth, the cells need to adapt to their new environment. The first phase of growth is the lag phase , a period of slow growth when the cells are adapting to the high-nutrient environment and preparing for fast growth. The lag phase has high biosynthesis rates, as proteins necessary for rapid growth are produced. The second phase of growth
1824-436: A possible treatment for various forms of gastroenteritis . As a treatment for infectious diarrhea, probiotics are of no benefit to people who have the condition for more than two days, and there is no evidence they lessen the duration of diarrhea overall. Probiotics are commonly given to breastfeeding mothers and their young children to prevent eczema ( dermatitis ), but no good evidence shows efficacy for this purpose. There
1938-469: A potentially fatal disease. Probiotic supplements typically contain between one and ten billion colony-forming units (CFUs) per dose. A higher number of CFUs does not provide additional probiotic effects, but may have unintended consequences of causing digestive discomfort, such as bloating, gas, and diarrhea. Lactobacillus species have been suggested to contribute to obesity in humans, but no evidence of this relationship has been found. In 2015,
2052-415: A process called transformation . Many bacteria can naturally take up DNA from the environment, while others must be chemically altered in order to induce them to take up DNA. The development of competence in nature is usually associated with stressful environmental conditions and seems to be an adaptation for facilitating repair of DNA damage in recipient cells. Second, bacteriophages can integrate into
2166-648: A professor at the Pasteur Institute in Paris , proposed the hypothesis that the aging process results from the activity of putrefactive ( proteolytic ) microbes producing toxic substances in the large bowel . Proteolytic bacteria such as clostridia , which are part of the normal gut microbiota, produce toxic substances including phenols , indols , and ammonia from the digestion of proteins . According to Metchnikoff , these compounds were responsible for what he called "intestinal autointoxication ", which would cause
2280-430: A result. A 2015 Cochrane review concluded that a protective effect of some probiotics existed for AAD in children. The known risks of using probiotics for treating Clostridioides difficile outweighs the uncertain benefits. Probiotic treatment might reduce the incidence and severity of AAD as indicated in several meta-analyses . For example, treatment with probiotic formulations including L. rhamnosus may reduce
2394-432: A risk exists for the passage of viable bacteria from the gastrointestinal tract to the internal organs (bacterial translocation) as a consequence of bacteremia , which can cause adverse health consequences. Rarely, consumption of probiotics by children with lowered immune system function or who are already critically ill may result in bacteremia or fungemia (i.e., bacteria or fungi in the blood), which can lead to sepsis ,
SECTION 20
#17328688657012508-425: A single continuous stretch of DNA. Although several different types of introns do exist in bacteria, these are much rarer than in eukaryotes. Bacteria, as asexual organisms, inherit an identical copy of the parent's genome and are clonal . However, all bacteria can evolve by selection on changes to their genetic material DNA caused by genetic recombination or mutations . Mutations arise from errors made during
2622-427: A single linear chromosome, while some Vibrio species contain more than one chromosome. Some bacteria contain plasmids , small extra-chromosomal molecules of DNA that may contain genes for various useful functions such as antibiotic resistance , metabolic capabilities, or various virulence factors . Bacteria genomes usually encode a few hundred to a few thousand genes. The genes in bacterial genomes are usually
2736-649: A source of electrons and a substrate for carbon anabolism . In many ways, bacterial metabolism provides traits that are useful for ecological stability and for human society. For example, diazotrophs have the ability to fix nitrogen gas using the enzyme nitrogenase . This trait, which can be found in bacteria of most metabolic types listed above, leads to the ecologically important processes of denitrification , sulfate reduction , and acetogenesis , respectively. Bacterial metabolic processes are important drivers in biological responses to pollution ; for example, sulfate-reducing bacteria are largely responsible for
2850-489: A strain of Escherichia coli from the feces of a soldier who was not affected by the disease. Methods of treating infectious diseases were needed at that time when antibiotics were not yet available, and Nissle used the E. coli Nissle 1917 strain in acute gastrointestinal infectious salmonellosis and shigellosis . In 1920, Rettger and Cheplin reported that Metchnikoff's "Bulgarian Bacillus", later called Lactobacillus delbrueckii subsp. bulgaricus , could not live in
2964-785: A thick peptidoglycan cell wall like a Gram-positive bacterium, but also a second outer layer of lipids. In many bacteria, an S-layer of rigidly arrayed protein molecules covers the outside of the cell. This layer provides chemical and physical protection for the cell surface and can act as a macromolecular diffusion barrier . S-layers have diverse functions and are known to act as virulence factors in Campylobacter species and contain surface enzymes in Bacillus stearothermophilus . Flagella are rigid protein structures, about 20 nanometres in diameter and up to 20 micrometres in length, that are used for motility . Flagella are driven by
3078-417: A three- dimensional random walk . Bacterial species differ in the number and arrangement of flagella on their surface; some have a single flagellum ( monotrichous ), a flagellum at each end ( amphitrichous ), clusters of flagella at the poles of the cell ( lophotrichous ), while others have flagella distributed over the entire surface of the cell ( peritrichous ). The flagella of a group of bacteria,
3192-496: Is a stub . You can help Misplaced Pages by expanding it . Bacteria See § Phyla Bacteria ( / b æ k ˈ t ɪər i ə / ; sg. : bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell . They constitute a large domain of prokaryotic microorganisms . Typically a few micrometres in length, bacteria were among the first life forms to appear on Earth , and are present in most of its habitats . Bacteria inhabit
3306-591: Is available. Kefir contains Lactobacillus acidophilus , Bifidobacterium bifidum , Streptococcus thermophilus , Lactobacillus delbrueckii subsp. bulgaricus, Lactobacillus helveticus, Lactobacillus kefiranofaciens , Lactococcus lactis , and Leuconostoc species. Buttermilk contains either Lactococcus lactis or L. bulgaricus . Other acidic bacteria, said to be probiotic, can be found in kombucha , including Gluconacetobacter xylinus , Zygosaccharomyces sp., Acetobacter pasteurianus, Acetobacter aceti , and Gluconobacter oxydans . The manipulation of
3420-480: Is caused by a toxin released by the bacteria that grow from the spores. Clostridioides difficile infection , a common problem in healthcare settings, is caused by spore-forming bacteria. Bacteria exhibit an extremely wide variety of metabolic types. The distribution of metabolic traits within a group of bacteria has traditionally been used to define their taxonomy , but these traits often do not correspond with modern genetic classifications. Bacterial metabolism
3534-412: Is classified into nutritional groups on the basis of three major criteria: the source of energy , the electron donors used, and the source of carbon used for growth. Phototrophic bacteria derive energy from light using photosynthesis , while chemotrophic bacteria breaking down chemical compounds through oxidation , driving metabolism by transferring electrons from a given electron donor to
Ureaplasma - Misplaced Pages Continue
3648-536: Is dependent on bacterial secretion systems . These transfer proteins from the cytoplasm into the periplasm or into the environment around the cell. Many types of secretion systems are known and these structures are often essential for the virulence of pathogens, so are intensively studied. Some genera of Gram-positive bacteria, such as Bacillus , Clostridium , Sporohalobacter , Anaerobacter , and Heliobacterium , can form highly resistant, dormant structures called endospores . Endospores develop within
3762-534: Is determined by the bacterial cell wall and cytoskeleton and is important because it can influence the ability of bacteria to acquire nutrients, attach to surfaces, swim through liquids and escape predators . Multicellularity . Most bacterial species exist as single cells; others associate in characteristic patterns: Neisseria forms diploids (pairs), streptococci form chains, and staphylococci group together in "bunch of grapes" clusters. Bacteria can also group to form larger multicellular structures, such as
3876-441: Is different from that of eukaryotes and archaea. Some bacteria produce intracellular nutrient storage granules, such as glycogen , polyphosphate , sulfur or polyhydroxyalkanoates . Bacteria such as the photosynthetic cyanobacteria , produce internal gas vacuoles , which they use to regulate their buoyancy, allowing them to move up or down into water layers with different light intensities and nutrient levels. Around
3990-414: Is essential to the survival of many bacteria, and the antibiotic penicillin (produced by a fungus called Penicillium ) is able to kill bacteria by inhibiting a step in the synthesis of peptidoglycan. There are broadly speaking two different types of cell wall in bacteria, that classify bacteria into Gram-positive bacteria and Gram-negative bacteria . The names originate from the reaction of cells to
4104-496: Is inconsistency in the results of different groups of 3488 children as reported in a Cochrane review. Also, it shows no significant difference regarding the adverse effects between probiotic and the other comparators. Only limited, low-quality evidence exists to indicate that probiotics are helpful for treating people with milk allergy . A 2015 review showed low-quality evidence that probiotics given directly to infants with eczema , or in infants whose mothers used probiotics during
4218-531: Is little evidence to support the use of probiotics to treat atopic dermatitis , and some risk of adverse effects . The American Academy of Dermatology stated: "The use of probiotics/prebiotics for the treatment of patients with established atopic dermatitis is not recommended due to inconsistent evidence". According to an umbrella review of meta-analyses of randomized controlled trials, probiotics supplementation reduces glucose homeostasis. This can be an effective therapy for lowering high blood sugar levels unless
4332-486: Is low-certainty evidence that probiotic supplements may increase the probability of clinical remission. People receiving probiotics were 73% more likely to experience disease remission and over 2x as likely to report improvement in symptoms compared to those receiving a placebo, with no clear difference in minor or serious adverse effects. Although there was no clear evidence of greater remission when probiotic supplements were compared with 5‐aminosalicylic acid treatment as
4446-529: Is made of about 20 proteins, with approximately another 30 proteins required for its regulation and assembly. The flagellum is a rotating structure driven by a reversible motor at the base that uses the electrochemical gradient across the membrane for power. Bacteria can use flagella in different ways to generate different kinds of movement. Many bacteria (such as E. coli ) have two distinct modes of movement: forward movement (swimming) and tumbling. The tumbling allows them to reorient and makes their movement
4560-468: Is made primarily of phospholipids . This membrane encloses the contents of the cell and acts as a barrier to hold nutrients, proteins and other essential components of the cytoplasm within the cell. Unlike eukaryotic cells , bacteria usually lack large membrane-bound structures in their cytoplasm such as a nucleus , mitochondria , chloroplasts and the other organelles present in eukaryotic cells. However, some bacteria have protein-bound organelles in
4674-496: Is motile in liquid or solid media. Several Listeria and Shigella species move inside host cells by usurping the cytoskeleton , which is normally used to move organelles inside the cell. By promoting actin polymerisation at one pole of their cells, they can form a kind of tail that pushes them through the host cell's cytoplasm. A few bacteria have chemical systems that generate light. This bioluminescence often occurs in bacteria that live in association with fish, and
Ureaplasma - Misplaced Pages Continue
4788-444: Is the stationary phase and is caused by depleted nutrients. The cells reduce their metabolic activity and consume non-essential cellular proteins. The stationary phase is a transition from rapid growth to a stress response state and there is increased expression of genes involved in DNA repair , antioxidant metabolism and nutrient transport . The final phase is the death phase where
4902-440: Is the logarithmic phase , also known as the exponential phase. The log phase is marked by rapid exponential growth . The rate at which cells grow during this phase is known as the growth rate ( k ), and the time it takes the cells to double is known as the generation time ( g ). During log phase, nutrients are metabolised at maximum speed until one of the nutrients is depleted and starts limiting growth. The third phase of growth
5016-480: Is the application or ingestion of bacterial species found in the healthy vagina to cure the infection of bacteria causing bacterial vaginosis . This treatment is based on the observation that 70% of healthy females have a group of bacteria in the genus Lactobacillus that dominate the population of organisms in the vagina. Specific strains of lactobacilli inhibit the growth of bacteria causing BV by producing H 2 O 2 , lactic acid, and/or bacteriocins, and/or inhibit
5130-676: Is the plural of the Neo-Latin bacterium , which is the Latinisation of the Ancient Greek βακτήριον ( baktḗrion ), the diminutive of βακτηρία ( baktēría ), meaning "staff, cane", because the first ones to be discovered were rod-shaped . The ancestors of bacteria were unicellular microorganisms that were the first forms of life to appear on Earth, about 4 billion years ago. For about 3 billion years, most organisms were microscopic, and bacteria and archaea were
5244-605: The European Food Safety Authority for insufficient evidence of beneficial mechanism or efficacy. An October 2001 report by the World Health Organization (WHO) defines probiotics as "live microorganisms which when administered in adequate amounts confer a health benefit on the host." Following this definition, a working group convened by the Food and Agriculture Organization (FAO)/WHO in May 2002 issued
5358-465: The European Food Safety Authority has rejected all petitions by commercial manufacturers for health claims on probiotic products in Europe due to insufficient evidence for a cause-and-effect mechanism for benefit, thus inconclusive proof of effectiveness. The European Commission placed a ban on putting the word "probiotic" on the packaging of products because such labeling misleads consumers to believe
5472-468: The Gram stain , a long-standing test for the classification of bacterial species. Gram-positive bacteria possess a thick cell wall containing many layers of peptidoglycan and teichoic acids . In contrast, Gram-negative bacteria have a relatively thin cell wall consisting of a few layers of peptidoglycan surrounded by a second lipid membrane containing lipopolysaccharides and lipoproteins . Most bacteria have
5586-535: The Greeks and Romans who recommended their consumption. The fermentation of dairy foods represents one of the oldest techniques for food preservation . The original modern hypothesis of the positive role played by certain bacteria was first introduced by Russian scientist and Nobel laureate Élie Metchnikoff , who in 1907 suggested that it would be possible to modify the gut microbiota and to replace harmful microbes with useful microbes. Metchnikoff, at that time
5700-768: The Guidelines for the Evaluation of Probiotics in Food . A consensus definition of the term probiotics , based on available information and scientific evidence, was adopted after the aforementioned joint expert consultation between the FAO of the United Nations and the WHO. This effort was accompanied by local governmental and supra-governmental regulatory bodies' requirements to better characterize health claims substantiations. That first global effort
5814-572: The Ministry of Health , in collaboration with other relevant authorities, oversees and addresses violations related to probiotic products. This includes issuing warnings, imposing administrative penalties, demanding product recalls and coordinating with other agencies. The National Yogurt Association (NYA) of the United States gives a "Live & Active Cultures Seal" to refrigerated yogurt products that contain 100 million cells per gram, or frozen yogurt products that contain 10 million cells per gram at
SECTION 50
#17328688657015928-601: The gut , though there are many on the skin. Most of the bacteria in and on the body are harmless or rendered so by the protective effects of the immune system , and many are beneficial , particularly the ones in the gut. However, several species of bacteria are pathogenic and cause infectious diseases , including cholera , syphilis , anthrax , leprosy , tuberculosis , tetanus and bubonic plague . The most common fatal bacterial diseases are respiratory infections . Antibiotics are used to treat bacterial infections and are also used in farming, making antibiotic resistance
6042-478: The intestine with harmless lactic-acid bacteria and decrease the intestinal pH, and that this would suppress the growth of proteolytic bacteria. Metchnikoff himself introduced in his diet sour milk fermented with the bacteria he called "Bulgarian Bacillus" and believed his health benefited. Friends in Paris soon followed his example and physicians began prescribing the sour-milk diet for their patients. Bifidobacteria
6156-610: The last trimester of pregnancy and breastfeeding, had lower risk of eczema. It is unclear whether probiotic supplementation helps with childhood asthma , as the quality of research evidence is low. Antibiotics are a common treatment for children, with 11% to 40% of antibiotic-treated children developing diarrhea . Antibiotic-associated diarrhea (AAD) results from an imbalance in the colonic microbiota caused by antibiotic therapy. These microbial community alterations result in changes in carbohydrate metabolism , with decreased short-chain fatty acid absorption and osmotic diarrhea as
6270-444: The spirochaetes , are found between two membranes in the periplasmic space. They have a distinctive helical body that twists about as it moves. Two other types of bacterial motion are called twitching motility that relies on a structure called the type IV pilus , and gliding motility , that uses other mechanisms. In twitching motility, the rod-like pilus extends out from the cell, binds some substrate, and then retracts, pulling
6384-546: The vacuum and radiation of outer space , leading to the possibility that bacteria could be distributed throughout the Universe by space dust , meteoroids , asteroids , comets , planetoids , or directed panspermia . Endospore-forming bacteria can cause disease; for example, anthrax can be contracted by the inhalation of Bacillus anthracis endospores, and contamination of deep puncture wounds with Clostridium tetani endospores causes tetanus , which, like botulism ,
6498-542: The FDA, so probiotic manufacturers have received warning letters for making disease or treatment claims. The FTC has taken punitive actions, including a US$ 21 million fine coordinated by 39 different state governments against a major probiotic manufacturer for deceptive advertising and exaggerated claims of health benefits for yogurt and probiotic dairy drink. In Vietnam , the Vietnam Food Administration (VFA) under
6612-781: The Gram-negative cell wall, and only members of the Bacillota group and actinomycetota (previously known as the low G+C and high G+C Gram-positive bacteria, respectively) have the alternative Gram-positive arrangement. These differences in structure can produce differences in antibiotic susceptibility; for instance, vancomycin can kill only Gram-positive bacteria and is ineffective against Gram-negative pathogens , such as Haemophilus influenzae or Pseudomonas aeruginosa . Some bacteria have cell wall structures that are neither classically Gram-positive or Gram-negative. This includes clinically important bacteria such as mycobacteria which have
6726-497: The Latin prae , meaning 'before', and refers to a substance that is not digested, but rather may be fermented to promote the growth of beneficial intestinal microorganisms. As food products or dietary supplements, probiotics are under preliminary research to evaluate if they provide any effect on health. In all cases proposed as health claims to the European Food Safety Authority , the scientific evidence remains insufficient to prove
6840-893: The ability to prevent food spoilage and can improve the nutritive value of the foods they inhabit. Acid fermentation (as well as salting), remains one of the most practical methods of preservation of fresh vegetables, cereal gruels, and milk-cereal mixtures due to its low cost and energy requirements. Fermented products that contain lactic acid bacteria include vegetables such as pickled vegetables , kimchi , pao cai , and sauerkraut ; sourdough bread or bread-like products made without wheat or rye flour , amino acid/peptide meat-flavored sauces and pastes produced by fermentation of cereals and legumes; fermented cereal-fish-shrimp mixtures and fermented meats; soy products such as tempeh , miso , and soy sauce ; dairy products such as yogurt , kefir , buttermilk ; and non-dairy products such as bee pollen . More precisely, sauerkraut contains
6954-517: The adherence of Gardnerella vaginalis to the vaginal epithelium, which prevents the infection from occurring in the vagina. Currently, the success of probiotic treatment has been mixed, since the use of probiotics to restore healthy populations of Lactobacillus has not been standardized. Often, standard antibiotic treatment is used at the same time that probiotics are being tested. In addition, some groups of women respond to treatment based upon ethnicity, age, number of sexual partners, pregnancy, and
SECTION 60
#17328688657017068-502: The air, soil, water, acidic hot springs , radioactive waste , and the deep biosphere of Earth's crust . Bacteria play a vital role in many stages of the nutrient cycle by recycling nutrients and the fixation of nitrogen from the atmosphere . The nutrient cycle includes the decomposition of dead bodies ; bacteria are responsible for the putrefaction stage in this process. In the biological communities surrounding hydrothermal vents and cold seeps , extremophile bacteria provide
7182-425: The archaeal/eukaryotic lineage. The most recent common ancestor (MRCA) of bacteria and archaea was probably a hyperthermophile that lived about 2.5 billion–3.2 billion years ago. The earliest life on land may have been bacteria some 3.22 billion years ago. Bacteria were also involved in the second great evolutionary divergence, that of the archaea and eukaryotes. Here, eukaryotes resulted from
7296-455: The atmosphere and one cubic metre of air holds around one hundred million bacterial cells. The oceans and seas harbour around 3 x 10 bacteria which provide up to 50% of the oxygen humans breathe. Only around 2% of bacterial species have been fully studied. Size . Bacteria display a wide diversity of shapes and sizes. Bacterial cells are about one-tenth the size of eukaryotic cells and are typically 0.5–5.0 micrometres in length. However,
7410-544: The bacteria Leuconostoc mesenteroides , Lactobacillus plantarum , Pediococcus pentosaceus, Lactobacillus brevis , Leuconostoc citreum, Leuconostoc argentinum, Lactobacillus paraplantarum , Lactobacillus coryniformis , and Weissella spp. Kimchi contains the bacteria Leuconostoc spp., Weissella spp., and Lactobacillus spp. Pao cai contains L. pentosus, L. plantarum , Leuconostoc mesenteroides , L. brevis, L. lactis , and L. fermentum . A list of many other bacteria found in several Asian fermented fruits and vegetables also
7524-520: The bacteria have come into contact with in the past, which allows them to block virus replication through a form of RNA interference . Third, bacteria can transfer genetic material through direct cell contact via conjugation . In ordinary circumstances, transduction, conjugation, and transformation involve transfer of DNA between individual bacteria of the same species, but occasionally transfer may occur between individuals of different bacterial species, and this may have significant consequences, such as
7638-444: The bacteria perform separate tasks; for example, about one in ten cells migrate to the top of a fruiting body and differentiate into a specialised dormant state called a myxospore, which is more resistant to drying and other adverse environmental conditions. Biofilms . Bacteria often attach to surfaces and form dense aggregations called biofilms and larger formations known as microbial mats . These biofilms and mats can range from
7752-401: The bacteria run out of nutrients and die. Most bacteria have a single circular chromosome that can range in size from only 160,000 base pairs in the endosymbiotic bacteria Carsonella ruddii , to 12,200,000 base pairs (12.2 Mbp) in the soil-dwelling bacteria Sorangium cellulosum . There are many exceptions to this; for example, some Streptomyces and Borrelia species contain
7866-412: The bacterial chromosome, introducing foreign DNA in a process known as transduction . Many types of bacteriophage exist; some infect and lyse their host bacteria, while others insert into the bacterial chromosome. Bacteria resist phage infection through restriction modification systems that degrade foreign DNA and a system that uses CRISPR sequences to retain fragments of the genomes of phage that
7980-663: The body becomes hypoglycemic ; caution and glucose monitoring are necessary to avoid this. Some strains of lactic acid bacteria (LAB) may affect Helicobacter pylori infections (which may cause peptic ulcers ) in adults when used in combination with standard medical treatments, but no standard in medical practice or regulatory approval exists for such treatment. The only peer-reviewed treatments for H. pylori to date all include various Antibiotic Regimens. Some strains of LAB may affect pathogens by means of competitive inhibition (i.e., by competing for growth) and some evidence suggests they may improve immune function by increasing
8094-437: The cell forward. Motile bacteria are attracted or repelled by certain stimuli in behaviours called taxes : these include chemotaxis , phototaxis , energy taxis , and magnetotaxis . In one peculiar group, the myxobacteria, individual bacteria move together to form waves of cells that then differentiate to form fruiting bodies containing spores. The myxobacteria move only when on solid surfaces, unlike E. coli , which
8208-576: The class Schizomycetes ("fission fungi"), bacteria are now classified as prokaryotes . Unlike cells of animals and other eukaryotes , bacterial cells do not contain a nucleus and rarely harbour membrane -bound organelles . Although the term bacteria traditionally included all prokaryotes, the scientific classification changed after the discovery in the 1990s that prokaryotes consist of two very different groups of organisms that evolved from an ancient common ancestor . These evolutionary domains are called Bacteria and Archaea . The word bacteria
8322-629: The cytoplasm of the cell; generally, a single endospore develops in each cell. Each endospore contains a core of DNA and ribosomes surrounded by a cortex layer and protected by a multilayer rigid coat composed of peptidoglycan and a variety of proteins. Endospores show no detectable metabolism and can survive extreme physical and chemical stresses, such as high levels of UV light , gamma radiation , detergents , disinfectants , heat, freezing, pressure, and desiccation . In this dormant state, these organisms may remain viable for millions of years. Endospores even allow bacteria to survive exposure to
8436-419: The cytoplasm which compartmentalise aspects of bacterial metabolism, such as the carboxysome . Additionally, bacteria have a multi-component cytoskeleton to control the localisation of proteins and nucleic acids within the cell, and to manage the process of cell division . Many important biochemical reactions, such as energy generation, occur due to concentration gradients across membranes, creating
8550-577: The definition used today. Fuller described probiotics as a "live microbial feed supplement which beneficially affects the host animal by improving its intestinal microbial balance." He stressed two important claims for probiotics: the viable nature of probiotics and the capacity to help with intestinal balance. In the following decades, intestinal lactic-acid bacterial species with alleged health-beneficial properties were introduced as probiotics, including Lactobacillus rhamnosus , Lactobacillus casei , and Lactobacillus johnsonii . Some literature gives
8664-433: The desired effect in this environment. In 1935, certain strains of L. acidophilus were found very active when implanted in the human digestive tract. Contrasting antibiotics, probiotics were defined as microbially derived factors that stimulate the growth of other microorganisms. In 1989, Roy Fuller suggested a definition of probiotics that have been widely used: "A live microbial feed supplement which beneficially affects
8778-411: The dominant forms of life. Although bacterial fossils exist, such as stromatolites , their lack of distinctive morphology prevents them from being used to examine the history of bacterial evolution, or to date the time of origin of a particular bacterial species. However, gene sequences can be used to reconstruct the bacterial phylogeny , and these studies indicate that bacteria diverged first from
8892-526: The elongated filaments of Actinomycetota species, the aggregates of Myxobacteria species, and the complex hyphae of Streptomyces species. These multicellular structures are often only seen in certain conditions. For example, when starved of amino acids, myxobacteria detect surrounding cells in a process known as quorum sensing , migrate towards each other, and aggregate to form fruiting bodies up to 500 micrometres long and containing approximately 100,000 bacterial cells. In these fruiting bodies,
9006-501: The energy released by the transfer of ions down an electrochemical gradient across the cell membrane. Fimbriae (sometimes called " attachment pili ") are fine filaments of protein, usually 2–10 nanometres in diameter and up to several micrometres in length. They are distributed over the surface of the cell, and resemble fine hairs when seen under the electron microscope . Fimbriae are believed to be involved in attachment to solid surfaces or to other cells, and are essential for
9120-597: The entering of ancient bacteria into endosymbiotic associations with the ancestors of eukaryotic cells, which were themselves possibly related to the Archaea. This involved the engulfment by proto-eukaryotic cells of alphaproteobacterial symbionts to form either mitochondria or hydrogenosomes , which are still found in all known Eukarya (sometimes in highly reduced form , e.g. in ancient "amitochondrial" protozoa). Later, some eukaryotes that already contained mitochondria also engulfed cyanobacteria -like organisms, leading to
9234-641: The evolution of different growth strategies (see r/K selection theory ). Some organisms can grow extremely rapidly when nutrients become available, such as the formation of algal and cyanobacterial blooms that often occur in lakes during the summer. Other organisms have adaptations to harsh environments, such as the production of multiple antibiotics by Streptomyces that inhibit the growth of competing microorganisms. In nature, many organisms live in communities (e.g., biofilms ) that may allow for increased supply of nutrients and protection from environmental stresses. These relationships can be essential for growth of
9348-566: The formation of chloroplasts in algae and plants. This is known as primary endosymbiosis . Bacteria are ubiquitous, living in every possible habitat on the planet including soil, underwater, deep in Earth's crust and even such extreme environments as acidic hot springs and radioactive waste. There are thought to be approximately 2×10 bacteria on Earth, forming a biomass that is only exceeded by plants. They are abundant in lakes and oceans, in arctic ice, and geothermal springs where they provide
9462-491: The global retail market value for probiotics was US$ 41 billion, including sales of probiotic supplements , fermented milk products, and yogurt, which alone accounted for 75% of total consumption. Innovation in probiotic products in 2015 was mainly from supplements, which produced US$ 4 billion and was projected to grow 37% globally by 2020. Consumption of yogurt products in China has increased by 20% per year since 2014. As of 2019 ,
9576-650: The growth in cell population. Probiotic Probiotics are live microorganisms promoted with claims that they provide health benefits when consumed, generally by improving or restoring the gut microbiota . Probiotics are considered generally safe to consume , but may cause bacteria - host interactions and unwanted side effects in rare cases. There is some evidence that probiotics are beneficial for some conditions, such as helping to ease some symptoms of irritable bowel syndrome (IBS). However, many claimed health benefits, such as treating eczema, lack substantial scientific support. The first discovered probiotic
9690-416: The growth of another microorganism. The term was used again to describe tissue extracts that stimulated microbial growth. The term probiotics was taken up by Parker, who defined the concept as, "Organisms and substances that have a beneficial effect on the host animal by contributing to its intestinal microbial balance." Later, the definition was greatly improved by Fuller, whose explanation was very close to
9804-426: The gut microbiota is complex and may cause bacteria-host interactions. Though probiotics are considered safe, some have concerns about their safety in certain cases. Some people, such as those with immunodeficiency , short bowel syndrome , central venous catheters , and cardiac valve disease , and premature infants, may be at higher risk for adverse events. In severely ill people with inflammatory bowel disease ,
9918-409: The host animal by improving its intestinal microbial balance." Fuller's definition emphasizes the requirement of viability for probiotics and introduces the aspect of a beneficial effect on the host. The term "probiotic" originally referred to microorganisms that have effects on other microorganisms. The concept of probiotics involved the notion that substances secreted by one microorganism stimulated
10032-400: The human intestine. They conducted experiments involving rats and humans volunteers, feeding them with Lactobacillus acidophilus . They observed the disappearance of the pathogenic protist Balantidium coli as well as of other gas-producing bacteria. Rettger further explored the possibilities of L. acidophilus , and reasoned that bacteria originating from the gut were more likely to produce
10146-646: The incidence of acute upper respiratory tract infections in adults, they were better than placebo or no treatment. Probiotics do not appear to change the risk of infection in older people. The use of oral probiotic supplements to modify the composition and behavior of the microbiome has been considered as a possible therapy for both induction and maintenance of remission in people with Crohn's disease and ulcerative colitis. A Cochrane review in 2020 did not find clear evidence of improved remission likelihood, nor lower adverse events, in people with Crohn's disease, following probiotic treatment. For ulcerative colitis, there
10260-627: The largest viruses . Some bacteria may be even smaller, but these ultramicrobacteria are not well-studied. Shape . Most bacterial species are either spherical, called cocci ( singular coccus , from Greek kókkos , grain, seed), or rod-shaped, called bacilli ( sing . bacillus, from Latin baculus , stick). Some bacteria, called vibrio , are shaped like slightly curved rods or comma-shaped; others can be spiral-shaped, called spirilla , or tightly coiled, called spirochaetes . A small number of other unusual shapes have been described, such as star-shaped bacteria. This wide variety of shapes
10374-716: The light probably serves to attract fish or other large animals. Bacteria often function as multicellular aggregates known as biofilms , exchanging a variety of molecular signals for intercell communication and engaging in coordinated multicellular behaviour. The communal benefits of multicellular cooperation include a cellular division of labour , accessing resources that cannot effectively be used by single cells, collectively defending against antagonists, and optimising population survival by differentiating into distinct cell types. For example, bacteria in biofilms can have more than five hundred times increased resistance to antibacterial agents than individual "planktonic" bacteria of
10488-581: The need for stricter requirements for scientific substantiation of putative benefits conferred by microorganisms claimed to be probiotic. Although some evidence claimed benefits are marketed towards using probiotic, such as reducing gastrointestinal discomfort, improving immune health , relieving constipation , or avoiding the common cold , such claims are strain-specific and cannot be extrapolated to other strains. As of 2019, numerous applications for approval of health claims by European manufacturers of probiotic dietary supplements have been rejected by
10602-417: The newly formed daughter cells. Examples include fruiting body formation by myxobacteria and aerial hyphae formation by Streptomyces species, or budding. Budding involves a cell forming a protrusion that breaks away and produces a daughter cell. In the laboratory, bacteria are usually grown using solid or liquid media. Solid growth media , such as agar plates , are used to isolate pure cultures of
10716-418: The number of IgA -producing plasma cells and increasing or improving phagocytosis , as well as increasing the proportion of T lymphocytes and natural killer cells. LAB products might aid in the treatment of acute diarrhea and possibly affect rotavirus infections in children and travelers' diarrhea in adults, but no products are approved for such indications. There are weak evidence probiotics might lower
10830-473: The nutrients needed to sustain life by converting dissolved compounds, such as hydrogen sulphide and methane , to energy. They live on and in plants and animals. Most do not cause diseases, are beneficial to their environments, and are essential for life. The soil is a rich source of bacteria and a few grams contain around a thousand million of them. They are all essential to soil ecology, breaking down toxic waste and recycling nutrients. They are even found in
10944-517: The nutrients needed to sustain life by converting dissolved compounds, such as hydrogen sulphide and methane , to energy. Bacteria also live in mutualistic , commensal and parasitic relationships with plants and animals. Most bacteria have not been characterised and there are many species that cannot be grown in the laboratory. The study of bacteria is known as bacteriology , a branch of microbiology . Like all animals, humans carry vast numbers (approximately 10 to 10 ) of bacteria. Most are in
11058-475: The outside of the cell membrane is the cell wall . Bacterial cell walls are made of peptidoglycan (also called murein), which is made from polysaccharide chains cross-linked by peptides containing D- amino acids . Bacterial cell walls are different from the cell walls of plants and fungi , which are made of cellulose and chitin , respectively. The cell wall of bacteria is also distinct from that of achaea, which do not contain peptidoglycan. The cell wall
11172-486: The pathogens causing bacterial vaginosis. In 2013, researchers found that administration of hydrogen peroxide -producing strains, such as L. acidophilus and L. rhamnosus , were able to normalize vaginal pH and rebalance the vaginal microbiota , preventing and alleviating bacterial vaginosis. As of 2017 , only limited evidence indicated any direct link between high blood pressure and gut microbiota. A 2002 meta-analysis that included five double-blind trials examining
11286-638: The physical changes associated with old age. At that time, milk fermented with lactobacillales were known to inhibit the growth of proteolytic bacteria because of the low pH produced by the fermentation of lactose . Metchnikoff had also observed that certain rural populations in Europe, for example in Bulgaria and the Russian steppes, who lived largely on milk fermented by lactic-acid bacteria, were exceptionally long-lived. Based on these observations, Metchnikoff proposed that consumption of fermented milk would "seed"
11400-612: The production of the highly toxic forms of mercury ( methyl- and dimethylmercury ) in the environment. Nonrespiratory anaerobes use fermentation to generate energy and reducing power, secreting metabolic by-products (such as ethanol in brewing) as waste. Facultative anaerobes can switch between fermentation and different terminal electron acceptors depending on the environmental conditions in which they find themselves. Unlike in multicellular organisms, increases in cell size ( cell growth ) and reproduction by cell division are tightly linked in unicellular organisms. Bacteria grow to
11514-560: The replication of DNA or from exposure to mutagens . Mutation rates vary widely among different species of bacteria and even among different clones of a single species of bacteria. Genetic changes in bacterial genomes emerge from either random mutation during replication or "stress-directed mutation", where genes involved in a particular growth-limiting process have an increased mutation rate. Some bacteria transfer genetic material between cells. This can occur in three main ways. First, bacteria can take up exogenous DNA from their environment in
11628-666: The risk of AAD, improve stool consistency during antibiotic therapy, and enhance the immune response after vaccination. The potential efficacy of probiotics to treat AAD depends on the probiotic strains and dosage. One review recommended for children L. rhamnosus or Saccharomyces boulardii at 5 to 40 billion colony-forming units/day, given the modest number needed to treat and the likelihood that adverse events are very rare. The same review stated that probiotic use should be avoided in pediatric populations at risk for adverse events , such as severely debilitated or immune-compromised children. Probiotic treatment of bacterial vaginosis
11742-530: The same species. One type of intercellular communication by a molecular signal is called quorum sensing , which serves the purpose of determining whether the local population density is sufficient to support investment in processes that are only successful if large numbers of similar organisms behave similarly, such as excreting digestive enzymes or emitting light. Quorum sensing enables bacteria to coordinate gene expression and to produce, release, and detect autoinducers or pheromones that accumulate with
11856-548: The short-term (2–8 weeks) effects of a yogurt with probiotic strains on serum cholesterol levels found little effect of 8.5 mg/dL (0.22 mmol/L) (4% decrease) in total cholesterol concentration, and a decrease of 7.7 mg/dL (0.2 mmol/L) (5% decrease) in serum LDL concentration. A 2019 meta-analysis found low-quality evidence for probiotics having a small improvement in depression and anxiety . A 2020 review found probiotics might improve depression, but more studies are needed. Some probiotics are suggested as
11970-412: The surfaces of plants, the majority of bacteria are bound to surfaces in biofilms. Biofilms are also important in medicine, as these structures are often present during chronic bacterial infections or in infections of implanted medical devices , and bacteria protected within biofilms are much harder to kill than individual isolated bacteria. The bacterial cell is surrounded by a cell membrane , which
12084-457: The terminal electron acceptor, while anaerobic organisms use other compounds such as nitrate , sulfate , or carbon dioxide. Many bacteria, called heterotrophs , derive their carbon from other organic carbon . Others, such as cyanobacteria and some purple bacteria , are autotrophic , meaning they obtain cellular carbon by fixing carbon dioxide . In unusual circumstances, the gas methane can be used by methanotrophic bacteria as both
12198-451: The time of consumption is difficult to determine. The survival of probiotics was strongly dependent on the storage temperature and remarkable viability loss occurred in room temperature compared to refrigerated storage. Probiotics have received renewed attention in the 21st century from product manufacturers, research studies, and consumers. Their history can be traced to the first use of cheese and fermented products, which were well-known to
12312-467: The time of manufacture. In 2002, the FDA and WHO recommended that "the minimum viable numbers of each probiotic strain at the end of the shelf-life" be reported on labeling, but most companies that give a number report the viable cell count at the date of manufacture, a number that could be much higher than that which exists at consumption. Because of the variability in storage conditions and time before eating, exactly how many active culture cells remain at
12426-447: The transfer of antibiotic resistance. In such cases, gene acquisition from other bacteria or the environment is called horizontal gene transfer and may be common under natural conditions. Many bacteria are motile (able to move themselves) and do so using a variety of mechanisms. The best studied of these are flagella , long filaments that are turned by a motor at the base to generate propeller-like movement. The bacterial flagellum
12540-495: The virulence of some bacterial pathogens. Pili ( sing . pilus) are cellular appendages, slightly larger than fimbriae, that can transfer genetic material between bacterial cells in a process called conjugation where they are called conjugation pili or sex pili (see bacterial genetics, below). They can also generate movement where they are called type IV pili . Glycocalyx is produced by many bacteria to surround their cells, and varies in structural complexity: ranging from
12654-457: The word a full Greek etymology , but it appears to be a composite of the Latin preposition pro , meaning 'for', and the Greek adjective βιωτικός ( biōtikos ), meaning 'fit for life, lively', the latter deriving from the noun βίος ( bios ), meaning 'life'. The term contrasts etymologically with the term antibiotic , although it is not a complete antonym . The related term prebiotic comes from
12768-458: Was a certain strain of bacillus in Bulgarian yoghurt, called Lactobacillus bulgaricus . The discovery was made in 1905 by Bulgarian physician and microbiologist Stamen Grigorov . The modern-day theory is generally attributed to Russian Nobel laureate Élie Metchnikoff , who postulated around 1907 that yoghurt -consuming Bulgarian peasants lived longer. A growing probiotics market has led to
12882-477: Was first isolated from a breastfed infant by Henry Tissier, who also worked at the Pasteur Institute . The isolated bacterium named Bacillus bifidus communis was later renamed to the genus Bifidobacterium . Tissier found that bifidobacteria are dominant in the gut microbiota of breast-fed babies and he observed clinical benefits from treating infant diarrhea with bifidobacteria. During an outbreak of shigellosis in 1917, German professor Alfred Nissle isolated
12996-481: Was further developed in 2010; two expert groups of academic scientists and industry representatives made recommendations for the evaluation and validation of probiotic health claims. The same principles emerged from those two groups as were expressed in the "Guidelines" of FAO/WHO in 2002. This definition, though widely adopted, is not acceptable to the European Food Safety Authority because it embeds
#700299