36-580: Burkholderiales Ferritrophicales Ferrovales Neisseriales Nitrosomonadales Procabacteriales Rhodocyclales Betaproteobacteria are a class of Gram-negative bacteria , and one of the eight classes of the phylum Pseudomonadota (synonym Proteobacteria). The Betaproteobacteria comprise over 75 genera and 400 species. Together, they represent a broad variety of metabolic strategies and occupy diverse environments, ranging from obligate pathogens living within host organisms to oligotrophic groundwater ecosystems. Whilst most members of
72-405: A microtubular spindle during nuclear division, in the distinctively eukaryotic process of mitosis . Eukaryotes differ from prokaryotes in multiple ways, with unique biochemical pathways such as sterane synthesis. The eukaryotic signature proteins have no homology to proteins in other domains of life, but appear to be universal among eukaryotes. They include the proteins of the cytoskeleton,
108-513: A "symbiosis-based phylogeny", giving the description "Eukarya (symbiosis-derived nucleated organisms)". By 2014, a rough consensus started to emerge from the phylogenomic studies of the previous two decades. The majority of eukaryotes can be placed in one of two large clades dubbed Amorphea (similar in composition to the unikont hypothesis) and the Diphoda (formerly bikonts), which includes plants and most algal lineages. A third major grouping,
144-430: A body, with its cells dividing by mitosis , and at some stage produce haploid gametes through meiosis , a division that reduces the number of chromosomes and creates genetic variability . There is considerable variation in this pattern. Plants have both haploid and diploid multicellular phases . Eukaryotes have lower metabolic rates and longer generation times than prokaryotes, because they are larger and therefore have
180-479: A bundle of microtubules arising from a centriole , characteristically arranged as nine doublets surrounding two singlets. Flagella may have hairs ( mastigonemes ), as in many stramenopiles . Their interior is continuous with the cell's cytoplasm . Centrioles are often present, even in cells and groups that do not have flagella, but conifers and flowering plants have neither. They generally occur in groups that give rise to various microtubular roots. These form
216-559: A membrane-bound nucleus . All animals , plants , fungi , and many unicellular organisms are eukaryotes. They constitute a major group of life forms alongside the two groups of prokaryotes : the Bacteria and the Archaea . Eukaryotes represent a small minority of the number of organisms, but given their generally much larger size, their collective global biomass is much larger than that of prokaryotes. The eukaryotes seemingly emerged within
252-406: A primary component of the cytoskeleton, and are often assembled over the course of several cell divisions, with one flagellum retained from the parent and the other derived from it. Centrioles produce the spindle during nuclear division. The cells of plants, algae, fungi and most chromalveolates , but not animals, are surrounded by a cell wall. This is a layer outside the cell membrane , providing
288-510: A smaller surface area to volume ratio. The evolution of sexual reproduction may be a primordial characteristic of eukaryotes. Based on a phylogenetic analysis, Dacks and Roger have proposed that facultative sex was present in the group's common ancestor. A core set of genes that function in meiosis is present in both Trichomonas vaginalis and Giardia intestinalis , two organisms previously thought to be asexual. Since these two species are descendants of lineages that diverged early from
324-417: A system of domains rather than kingdoms as top level rank being put forward by Carl Woese , Otto Kandler , and Mark Wheelis in 1990, uniting all the eukaryote kingdoms in the domain "Eucarya", stating, however, that " 'eukaryotes' will continue to be an acceptable common synonym". In 1996, the evolutionary biologist Lynn Margulis proposed to replace kingdoms and domains with "inclusive" names to create
360-610: Is closer in structure to bacterial RNA than to eukaryote RNA. Some eukaryotes, such as the metamonads Giardia and Trichomonas , and the amoebozoan Pelomyxa , appear to lack mitochondria, but all contain mitochondrion-derived organelles, like hydrogenosomes or mitosomes , having lost their mitochondria secondarily. They obtain energy by enzymatic action in the cytoplasm. Plants and various groups of algae have plastids as well as mitochondria. Plastids, like mitochondria, have their own DNA and are developed from endosymbionts , in this case cyanobacteria . They usually take
396-683: Is potentially dangerous because high ammonium content can lead to eutrophication . Biological wastewater treatment systems, as well as other biological ammonium-removing methods, depend on the metabolism of various Bacteria including members of the Nitrosomonadales of the Betaproteobacteria that perform nitrification to remove excessive ammonia from wastewater. The ammonia is first oxidized into nitrite , further oxidized to nitrate . A variety of other organisms then reduces nitrate into molecular nitrogen gas ( denitrification ), which leaves
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#1732852328338432-532: Is that their cells have nuclei . This gives them their name, from the Greek εὖ ( eu , "well" or "good") and κάρυον ( karyon , "nut" or "kernel", here meaning "nucleus"). Eukaryotic cells have a variety of internal membrane-bound structures, called organelles , and a cytoskeleton which defines the cell's organization and shape. The nucleus stores the cell's DNA , which is divided into linear bundles called chromosomes ; these are separated into two matching sets by
468-626: The Burkholderiales , the Neisseriales , the Nitrosomonadales and the Rhodocyclales . The name " Procabacteriales " was also proposed for an order of endosymbionts of Acanthamoeba , but since they cannot be grown in culture and studies have been limited, the name has never been validly or effectively published, and thus is no more than a nickname without any standing in nomenclature. An extensive reclassification of families and orders of
504-947: The Nitrosomonadales . The four orders of the Betaproteobacteria are: Some members of the Betaproteobacteria can cause disease in various eukaryotic organisms, including humans. For example, Neisseria gonorrhoeae and N. meningitidis cause gonorrhea and meningitis respectively, while Bordetella pertussis causes whooping cough . Other members of the class infect plants, such as Ralstonia solanacearum which causes bacterial wilt disease of over 250 plant species, Burkholderia cepacia which causes bulb rot in onions, and Xylophilus ampelinus which causes necrosis of grapevines. Betaproteobacteria play an important role in denitrification, removal of phosphorus, and xenobiotic degradation from waste. Various human activities, such as fertilizer production and chemical plant usage, release significant amounts of ammonium ions into rivers and oceans. Ammonium buildup in aquatic environments
540-659: The Asgard archaea , and are closely related to the Heimdallarchaeia . This implies that there are only two domains of life , Bacteria and Archaea, with eukaryotes incorporated among the Archaea. Eukaryotes first emerged during the Paleoproterozoic , likely as flagellated cells. The leading evolutionary theory is they were created by symbiogenesis between an anaerobic Asgard archaean and an aerobic proteobacterium , which formed
576-606: The Betaproteobacteria are heterotrophic , deriving both their carbon and electrons from organocarbon sources, some are photoheterotrophic , deriving energy from light and carbon from organocarbon sources. Other genera are autotrophic , deriving their carbon from bicarbonate or carbon dioxide and their electrons from reduced inorganic ions such as nitrite , ammonium , thiosulfate or sulfide — many of these chemolithoautotrophic . Betaproteobacteria are economically important, with roles in maintaining soil pH and in elementary cycling. Some economically important members of
612-427: The Betaproteobacteria use nitrate as their terminal electron acceptor and can be used industrially to remove nitrate from wastewater by denitrification . A number of Betaproteobacteria are diazotrophs , meaning that they can fix molecular nitrogen from the air as their nitrogen source for growth – this is important to the farming industry as it is a primary means of ammonium levels in soils rising without
648-518: The archaea —having a volume of around 10,000 times greater. Eukaryotes represent a small minority of the number of organisms , but, as many of them are much larger, their collective global biomass (468 gigatons) is far larger than that of prokaryotes (77 gigatons), with plants alone accounting for over 81% of the total biomass of Earth . The eukaryotes are a diverse lineage, consisting mainly of microscopic organisms . Multicellularity in some form has evolved independently at least 25 times within
684-583: The blue whale , weighing up to 190 tonnes and measuring up to 33.6 metres (110 ft) long, or plants like the coast redwood , up to 120 metres (390 ft) tall. Many eukaryotes are unicellular; the informal grouping called protists includes many of these, with some multicellular forms like the giant kelp up to 200 feet (61 m) long. The multicellular eukaryotes include the animals, plants, and fungi , but again, these groups too contain many unicellular species . Eukaryotic cells are typically much larger than those of prokaryotes —the bacteria and
720-740: The mitochondria . A second episode of symbiogenesis with a cyanobacterium created the plants, with chloroplasts . Eukaryotic cells contain membrane-bound organelles such as the nucleus , the endoplasmic reticulum , and the Golgi apparatus . Eukaryotes may be either unicellular or multicellular . In comparison, prokaryotes are typically unicellular. Unicellular eukaryotes are sometimes called protists . Eukaryotes can reproduce both asexually through mitosis and sexually through meiosis and gamete fusion ( fertilization ). Eukaryotes are organisms that range from microscopic single cells , such as picozoans under 3 micrometres across, to animals like
756-430: The photosynthetic purple nonsulfur bacteria ), and Herbaspirillum (capable of nitrogen-fixation ). This Betaproteobacteria -related article is a stub . You can help Misplaced Pages by expanding it . Eukaryote The eukaryotes ( / j uː ˈ k ær i oʊ t s , - ə t s / yoo- KARR -ee-ohts, -əts ) constitute the domain of Eukaryota or Eukarya , organisms whose cells have
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#1732852328338792-510: The taxonomic rank of kingdom by Linnaeus in the 18th century. Though he included the fungi with plants with some reservations, it was later realized that they are quite distinct and warrant a separate kingdom. The various single-cell eukaryotes were originally placed with plants or animals when they became known. In 1818, the German biologist Georg A. Goldfuss coined the word Protozoa to refer to organisms such as ciliates , and this group
828-709: The cell to move, change shape, or transport materials. The motor structures are microfilaments of actin and actin-binding proteins , including α- actinin , fimbrin , and filamin are present in submembranous cortical layers and bundles. Motor proteins of microtubules, dynein and kinesin , and myosin of actin filaments, provide dynamic character of the network. Many eukaryotes have long slender motile cytoplasmic projections, called flagella , or multiple shorter structures called cilia . These organelles are variously involved in movement, feeding, and sensation. They are composed mainly of tubulin , and are entirely distinct from prokaryotic flagella. They are supported by
864-404: The cell with structural support, protection, and a filtering mechanism. The cell wall also prevents over-expansion when water enters the cell. The major polysaccharides making up the primary cell wall of land plants are cellulose , hemicellulose , and pectin . The cellulose microfibrils are linked together with hemicellulose, embedded in a pectin matrix. The most common hemicellulose in
900-469: The class based on a polyphasic analysis (including 16S rRNA gene analyses and 53-protein ribosomal protein concatamer analyses using the rMLST Multilocus sequence typing system) was published in 2017, that removed the order Hydrogenophilales from the class and into a novel class of the " Pseudomonadota ", the Hydrogenophilalia . The same study also merged the former order Methylophilales into
936-427: The complex transcription machinery, the membrane-sorting systems, the nuclear pore , and some enzymes in the biochemical pathways. Eukaryote cells include a variety of membrane-bound structures, together forming the endomembrane system. Simple compartments, called vesicles and vacuoles , can form by budding off other membranes. Many cells ingest food and other materials through a process of endocytosis , where
972-622: The cytoplasm. Mitochondria are organelles in eukaryotic cells. The mitochondrion is commonly called "the powerhouse of the cell", for its function providing energy by oxidising sugars or fats to produce the energy-storing molecule ATP . Mitochondria have two surrounding membranes , each a phospholipid bilayer , the inner of which is folded into invaginations called cristae where aerobic respiration takes place. Mitochondria contain their own DNA , which has close structural similarities to bacterial DNA , from which it originated, and which encodes rRNA and tRNA genes that produce RNA which
1008-924: The ecosystem and is carried into the atmosphere. Burkholderiales The Burkholderiales are an order of Betaproteobacteria in the phylum Pseudomonadota . Like all Pseudomonadota , they are Gram-negative . They include several pathogenic bacteria, including species of Burkholderia , Bordetella , and Ralstonia . They also include Oxalobacter and related genera, which are unusual in using oxalic acid as their source of carbon. Other well-studied genera include Alcaligenes , Cupriavidus , Achromobacter , Comamonas , Delftia , Massilia , Duganella , Janthinobacterium , Polynucleobacter (important freshwater bacterioplankton ), non-pathogenic Paraburkholderia , Caballeronia , Polaromonas , Thiomonas , Collimonas , Hydrogenophaga , Sphaerotilus , Variovorax , Acidovorax , Rubrivivax and Rhodoferax (both members of
1044-406: The eukaryotes. Complex multicellular organisms, not counting the aggregation of amoebae to form slime molds , have evolved within only six eukaryotic lineages: animals , symbiomycotan fungi , brown algae , red algae , green algae , and land plants . Eukaryotes are grouped by genomic similarities, so that groups often lack visible shared characteristics. The defining feature of eukaryotes
1080-484: The eukaryotic evolutionary tree, core meiotic genes, and hence sex, were likely present in the common ancestor of eukaryotes. Species once thought to be asexual, such as Leishmania parasites, have a sexual cycle. Amoebae, previously regarded as asexual, may be anciently sexual; while present-day asexual groups could have arisen recently. In antiquity , the two lineages of animals and plants were recognized by Aristotle and Theophrastus . The lineages were given
1116-646: The form of chloroplasts which, like cyanobacteria, contain chlorophyll and produce organic compounds (such as glucose ) through photosynthesis . Others are involved in storing food. Although plastids probably had a single origin, not all plastid-containing groups are closely related. Instead, some eukaryotes have obtained them from others through secondary endosymbiosis or ingestion. The capture and sequestering of photosynthetic cells and chloroplasts, kleptoplasty , occurs in many types of modern eukaryotic organisms. The cytoskeleton provides stiffening structure and points of attachment for motor structures that enable
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1152-449: The outer membrane invaginates and then pinches off to form a vesicle. Some cell products can leave in a vesicle through exocytosis . The nucleus is surrounded by a double membrane known as the nuclear envelope , with nuclear pores that allow material to move in and out. Various tube- and sheet-like extensions of the nuclear membrane form the endoplasmic reticulum , which is involved in protein transport and maturation. It includes
1188-548: The presence of leguminous plants . The Betaproteobacteria are one of the eight classes that make up the Pseudomonadota ("Proteobacteria"). The Betaproteobacteria are most closely related to the Gammaproteobacteria , Acidithiobacillia and Hydrogenophilalia , which together make up a taxon which has previously been called " Chromatibacteria ". Four orders of Betaproteobacteria are currently recognised —
1224-417: The primary cell wall is xyloglucan . Eukaryotes have a life cycle that involves sexual reproduction , alternating between a haploid phase, where only one copy of each chromosome is present in each cell, and a diploid phase, with two copies of each chromosome in each cell. The diploid phase is formed by fusion of two haploid gametes, such as eggs and spermatozoa , to form a zygote ; this may grow into
1260-498: The rough endoplasmic reticulum, covered in ribosomes which synthesize proteins; these enter the interior space or lumen. Subsequently, they generally enter vesicles, which bud off from the smooth endoplasmic reticulum. In most eukaryotes, these protein-carrying vesicles are released and further modified in stacks of flattened vesicles ( cisternae ), the Golgi apparatus . Vesicles may be specialized; for instance, lysosomes contain digestive enzymes that break down biomolecules in
1296-498: Was expanded until Ernst Haeckel made it a kingdom encompassing all single-celled eukaryotes, the Protista , in 1866. The eukaryotes thus came to be seen as four kingdoms: The protists were at that time thought to be "primitive forms", and thus an evolutionary grade , united by their primitive unicellular nature. Understanding of the oldest branchings in the tree of life only developed substantially with DNA sequencing , leading to
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