β-proteobacteria
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''Betaproteobacteria'' are a class of
Gram-negative bacteria Gram-negative bacteria are bacteria that, unlike gram-positive bacteria, do not retain the Crystal violet, crystal violet stain used in the Gram staining method of bacterial differentiation. Their defining characteristic is that their cell envelo ...
, and one of the six classes of the
phylum In biology, a phylum (; : phyla) is a level of classification, or taxonomic rank, that is below Kingdom (biology), kingdom and above Class (biology), class. Traditionally, in botany the term division (taxonomy), division has been used instead ...
''
Pseudomonadota Pseudomonadota (synonym "Proteobacteria") is a major phylum of gram-negative bacteria. Currently, they are considered the predominant phylum within the domain of bacteria. They are naturally found as pathogenic and free-living (non- parasitic) ...
'' (synonym Proteobacteria).


Metabolism

The ''Betaproteobacteria'' comprise over 75
genera Genus (; : genera ) is a taxonomic rank above species and below family as used in the biological classification of living and fossil organisms as well as viruses. In binomial nomenclature, the genus name forms the first part of the binomial s ...
and 400 species. Together, they represent a broad variety of metabolic strategies and occupy diverse environments, ranging from obligate
pathogen In biology, a pathogen (, "suffering", "passion" and , "producer of"), in the oldest and broadest sense, is any organism or agent that can produce disease. A pathogen may also be referred to as an infectious agent, or simply a Germ theory of d ...
s living within host organisms to oligotrophic groundwater ecosystems. Whilst most members of the ''Betaproteobacteria'' are
heterotrophic A heterotroph (; ) is an organism that cannot produce its own food, instead taking nutrition from other sources of organic carbon, mainly plant or animal matter. In the food chain, heterotrophs are primary, secondary and tertiary consumers, but ...
, deriving both their carbon and electrons from organocarbon sources, some are
photoheterotroph Photoheterotrophs (''Greek language, Gk'': ''photo'' = light, ''hetero'' = (an)other, ''troph'' = nourishment) are heterotrophic phototrophs—that is, they are organisms that use light for energy, but cannot use carbon dioxide as their sole carbon ...
ic, deriving energy from light and carbon from organocarbon sources. Other genera are
autotroph An autotroph is an organism that can convert Abiotic component, abiotic sources of energy into energy stored in organic compounds, which can be used by Heterotroph, other organisms. Autotrophs produce complex organic compounds (such as carbohy ...
ic, deriving their carbon from
bicarbonate In inorganic chemistry, bicarbonate (IUPAC-recommended nomenclature: hydrogencarbonate) is an intermediate form in the deprotonation of carbonic acid. It is a polyatomic anion with the chemical formula . Bicarbonate serves a crucial bioche ...
or
carbon dioxide Carbon dioxide is a chemical compound with the chemical formula . It is made up of molecules that each have one carbon atom covalent bond, covalently double bonded to two oxygen atoms. It is found in a gas state at room temperature and at norma ...
and their electrons from reduced
inorganic An inorganic compound is typically a chemical compound that lacks carbon–hydrogen bonds⁠that is, a compound that is not an organic compound. The study of inorganic compounds is a subfield of chemistry known as '' inorganic chemistry''. Inor ...
ion An ion () is an atom or molecule with a net electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by convent ...
s such as
nitrite The nitrite polyatomic ion, ion has the chemical formula . Nitrite (mostly sodium nitrite) is widely used throughout chemical and pharmaceutical industries. The nitrite anion is a pervasive intermediate in the nitrogen cycle in nature. The name ...
,
ammonium Ammonium is a modified form of ammonia that has an extra hydrogen atom. It is a positively charged (cationic) polyatomic ion, molecular ion with the chemical formula or . It is formed by the protonation, addition of a proton (a hydrogen nucleu ...
,
thiosulfate Thiosulfate ( IUPAC-recommended spelling; sometimes thiosulphate in British English) is an oxyanion of sulfur with the chemical formula . Thiosulfate also refers to the compounds containing this anion, which are the salts of thiosulfuric acid, ...
or
sulfide Sulfide (also sulphide in British English) is an inorganic anion of sulfur with the chemical formula S2− or a compound containing one or more S2− ions. Solutions of sulfide salts are corrosive. ''Sulfide'' also refers to large families o ...
— many of these
chemolithoautotrophic A lithoautotroph is an organism that derives energy from reactions of reduced compounds of mineral (inorganic) origin. Two types of lithoautotrophs are distinguished by their energy source; photolithoautotrophs derive their energy from light, whil ...
. ''Betaproteobacteria'' are economically important, with roles in maintaining
soil pH Soil pH is a measure of the acidity or basicity (alkalinity) of a soil. Soil pH is a key characteristic that can be used to make informative analysis both qualitative and quantitatively regarding soil characteristics. pH is defined as the neg ...
and in elementary cycling. Some economically important members of the ''Betaproteobacteria'' use
nitrate Nitrate is a polyatomic ion with the chemical formula . salt (chemistry), Salts containing this ion are called nitrates. Nitrates are common components of fertilizers and explosives. Almost all inorganic nitrates are solubility, soluble in wa ...
as their
terminal electron acceptor An electron acceptor is a chemical entity that accepts electrons transferred to it from another compound. Electron acceptors are oxidizing agents. The electron accepting power of an electron acceptor is measured by its redox potential. In the si ...
and can be used industrially to remove
nitrate Nitrate is a polyatomic ion with the chemical formula . salt (chemistry), Salts containing this ion are called nitrates. Nitrates are common components of fertilizers and explosives. Almost all inorganic nitrates are solubility, soluble in wa ...
from
wastewater Wastewater (or waste water) is water generated after the use of freshwater, raw water, drinking water or saline water in a variety of deliberate applications or processes. Another definition of wastewater is "Used water from any combination of do ...
by
denitrification Denitrification is a microbially facilitated process where nitrate (NO3−) is reduced and ultimately produces molecular nitrogen (N2) through a series of intermediate gaseous nitrogen oxide products. Facultative anaerobic bacteria perform denitr ...
. A number of ''Betaproteobacteria'' are
diazotroph Diazotrophs are organisms capable of nitrogen fixation, i.e. converting the relatively inert diatomic nitrogen (N2) in Earth's atmosphere into bioavailable compound forms such as ammonia. Diazotrophs are typically microorganisms such as bacteria ...
s, meaning that they can fix molecular
nitrogen Nitrogen is a chemical element; it has Symbol (chemistry), symbol N and atomic number 7. Nitrogen is a Nonmetal (chemistry), nonmetal and the lightest member of pnictogen, group 15 of the periodic table, often called the Pnictogen, pnictogens. ...
from the air as their nitrogen source for growth – this is important to the farming industry as it is a primary means of
ammonium Ammonium is a modified form of ammonia that has an extra hydrogen atom. It is a positively charged (cationic) polyatomic ion, molecular ion with the chemical formula or . It is formed by the protonation, addition of a proton (a hydrogen nucleu ...
levels in soils rising without the presence of leguminous plants.


Phylogeny

The ''Betaproteobacteria'' are one of the eight classes that make up the ''
Pseudomonadota Pseudomonadota (synonym "Proteobacteria") is a major phylum of gram-negative bacteria. Currently, they are considered the predominant phylum within the domain of bacteria. They are naturally found as pathogenic and free-living (non- parasitic) ...
'' ("Proteobacteria"). The ''Betaproteobacteria'' are most closely related to the ''
Gammaproteobacteria ''Gammaproteobacteria'' is a class of bacteria in the phylum ''Pseudomonadota'' (synonym ''Proteobacteria''). It contains about 250 genera, which makes it the most genus-rich taxon of the Prokaryotes. Several medically, ecologically, and scienti ...
'', ''
Acidithiobacillia ''Acidithiobacillia'' is a class of the phylum '' Pseudomonadota'' ("Proteobacteria"). Its type order, the ''Acidithiobacillales'', was formerly classified within the '' Gammaproteobacteria'', and comprises two families of sulfur-oxidising autot ...
'' and ''
Hydrogenophilalia The ''Hydrogenophilaceae'' are a family of the class '' Hydrogenophilalia'' in the phylum ''Pseudomonadota'' ("Proteobacteria"), with two genera – '' Hydrogenophilus'' and '' Tepidiphilus''. Like all ''Pseudomonadota'', they are Gram-negative. ...
'', which together make up a
taxon In biology, a taxon (back-formation from ''taxonomy''; : taxa) is a group of one or more populations of an organism or organisms seen by taxonomists to form a unit. Although neither is required, a taxon is usually known by a particular name and ...
which has previously been called " Chromatibacteria". Four orders of ''Betaproteobacteria'' are currently recognised — the ''
Burkholderiales The Burkholderiales are an order of ''Betaproteobacteria'' in the phylum ''Pseudomonadota''.George M. Garrity: '' Bergey's Manual of Systematic Bacteriology''. 2. Auflage. Springer, New York, 2005, Vol. 2: ''The Proteobacteria Part C: The Alpha-, ...
'', the ''
Neisseriales The Neisseriaceae are a family of '' Pseudomonadota'', within the '' Neisseriales'' order of ''Betaproteobacteria''. While many organisms in the family are mammalian commensals or part of the normal flora, the genus '' Neisseria'' includes two i ...
'', the ''
Nitrosomonadales The ''Nitrosomonadales'' are an order of the class ''Betaproteobacteria'' in the phylum ''Pseudomonadota''.Garrity, George M.; Brenner, Don J.; Krieg, Noel R.; Staley, James T. (eds.) (2005). Bergey's Manual of Systematic Bacteriology, Volume Two ...
'' and the ''
Rhodocyclales The Rhodocyclales are an order of the class Betaproteobacteria in the phylum Pseudomonadota ("Proteobacteria").Garrity, George M.; Brenner, Don J.; Krieg, Noel R.; Staley, James T. (eds.) (2005). Bergey's Manual of Systematic Bacteriology, Volum ...
''. The name "
Procabacteriales "Procabacteriaceae" is a ''Candidatus'' family of uncultivated Gram-negative ''Betaproteobacteria''. The sole genus, ''"Candidatus'' Procabacter''"'', was identified as an obligate endosymbiont of ''Acanthamoeba ''Acanthamoeba'' is a genus ...
" was also proposed for an order of
endosymbiont An endosymbiont or endobiont is an organism that lives within the body or cells of another organism. Typically the two organisms are in a mutualism (biology), mutualistic relationship. Examples are nitrogen-fixing bacteria (called rhizobia), whi ...
s of ''
Acanthamoeba ''Acanthamoeba'' is a genus of amoeboid, amoebae that are commonly recovered from soil, fresh water, and other habitat (ecology), habitats. The genus ''Acanthamoeba'' has two stages in its life cycle, the metabolically active trophozoite stage a ...
'', 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 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 Multilocus sequence typing (MLST) is a technique in molecular biology for the typing of multiple loci, using DNA sequences of internal fragments of multiple housekeeping genes to characterize isolates of microbial species. The first MLST scheme ...
system) was published in 2017, that removed the order ''
Hydrogenophilales The ''Hydrogenophilaceae'' are a family of the class ''Hydrogenophilalia'' in the phylum ''Pseudomonadota'' ("Proteobacteria"), with two genera – '' Hydrogenophilus'' and '' Tepidiphilus''. Like all ''Pseudomonadota'', they are Gram-negative. A ...
'' from the class and into a novel class of the "
Pseudomonadota Pseudomonadota (synonym "Proteobacteria") is a major phylum of gram-negative bacteria. Currently, they are considered the predominant phylum within the domain of bacteria. They are naturally found as pathogenic and free-living (non- parasitic) ...
", the ''
Hydrogenophilalia The ''Hydrogenophilaceae'' are a family of the class '' Hydrogenophilalia'' in the phylum ''Pseudomonadota'' ("Proteobacteria"), with two genera – '' Hydrogenophilus'' and '' Tepidiphilus''. Like all ''Pseudomonadota'', they are Gram-negative. ...
''. The same study also merged the former order '' Methylophilales'' into the ''
Nitrosomonadales The ''Nitrosomonadales'' are an order of the class ''Betaproteobacteria'' in the phylum ''Pseudomonadota''.Garrity, George M.; Brenner, Don J.; Krieg, Noel R.; Staley, James T. (eds.) (2005). Bergey's Manual of Systematic Bacteriology, Volume Two ...
''. The four orders of the ''Betaproteobacteria'' are: * ''
Burkholderiales The Burkholderiales are an order of ''Betaproteobacteria'' in the phylum ''Pseudomonadota''.George M. Garrity: '' Bergey's Manual of Systematic Bacteriology''. 2. Auflage. Springer, New York, 2005, Vol. 2: ''The Proteobacteria Part C: The Alpha-, ...
'' (type order) comprises the families '' Burkholderiacae'' (type family), '' Alcaliginaceae'', ''
Comamonadaceae The Comamonadaceae are a family of the Betaproteobacteria.Willems A., J. De Ley, M. Gillis, and K. Kersters. ''Comamonadaceae, a New Family Encompassing the Acidovorans rRNA Complex, Including Variovorax paradoxus gen. nov.,comb. nov. for Alcali ...
'', ''
Oxalobacteraceae The Oxalobacteraceae are a family of bacteria, included in the order Burkholderiales. Like all Pseudomonadota, Oxalobacteraceae are Gram-negative. The family includes strict aerobes, strict anaerobes, and nitrogen-fixing Nitrogen fixation is ...
'' and '' Sutterellaceae''. They exhibit a range of morphologies, including rods, curved rods, cocci, spirillae and multicellular 'tablets'. Both
heterotrophs A heterotroph (; ) is an organism that cannot produce its own food, instead taking nutrition from other sources of organic carbon, mainly plant or animal matter. In the food chain, heterotrophs are primary, secondary and tertiary consumers, but ...
and photoheterotrophs are found along with some facultative
autotrophs An autotroph is an organism that can convert abiotic sources of energy into energy stored in organic compounds, which can be used by other organisms. Autotrophs produce complex organic compounds (such as carbohydrates, fats, and proteins) us ...
. * ''
Neisseriales The Neisseriaceae are a family of '' Pseudomonadota'', within the '' Neisseriales'' order of ''Betaproteobacteria''. While many organisms in the family are mammalian commensals or part of the normal flora, the genus '' Neisseria'' includes two i ...
'' comprises the families '' Neisseriaceae'' (type family) and '' Chromobacteriaceae''. Their morphologies include cocci, curved rods, spirillae, rods, multicellular ribbons and filaments. Most are
heterotrophs A heterotroph (; ) is an organism that cannot produce its own food, instead taking nutrition from other sources of organic carbon, mainly plant or animal matter. In the food chain, heterotrophs are primary, secondary and tertiary consumers, but ...
with some facultative methylotrophs and chemolithoheterotrophs. * ''
Nitrosomonadales The ''Nitrosomonadales'' are an order of the class ''Betaproteobacteria'' in the phylum ''Pseudomonadota''.Garrity, George M.; Brenner, Don J.; Krieg, Noel R.; Staley, James T. (eds.) (2005). Bergey's Manual of Systematic Bacteriology, Volume Two ...
'' comprises the families ''
Nitrosomonadaceae The ''Nitrosomonadales'' are an order of the class ''Betaproteobacteria'' in the phylum ''Pseudomonadota''.Garrity, George M.; Brenner, Don J.; Krieg, Noel R.; Staley, James T. (eds.) (2005). Bergey's Manual of Systematic Bacteriology, Volume Two ...
'' (type family), '' Methylophilacae'', '' Thiobacillaceae'', '' Sterolibacteriacae'', ''
Spirillaceae Spirillaceae is a family in the order ''Nitrosomonadales'' in the class ''Betaproteobacteria'' of the bacteria Bacteria (; : bacterium) are ubiquitous, mostly free-living organisms often consisting of one Cell (biology), biological cell ...
'' and '' Gallionellaceae''. Their morphologies include rods, spirillae and curved rods. Most are chemolithoautotrophs with some methylotrophs and
heterotrophs A heterotroph (; ) is an organism that cannot produce its own food, instead taking nutrition from other sources of organic carbon, mainly plant or animal matter. In the food chain, heterotrophs are primary, secondary and tertiary consumers, but ...
* ''
Rhodocyclales The Rhodocyclales are an order of the class Betaproteobacteria in the phylum Pseudomonadota ("Proteobacteria").Garrity, George M.; Brenner, Don J.; Krieg, Noel R.; Staley, James T. (eds.) (2005). Bergey's Manual of Systematic Bacteriology, Volum ...
'' comprises the families ''
Rhodocyclaceae The ''Rhodocyclaceae'' are a family of gram-negative bacteria.Garrity, George M.; Brenner, Don J.; Krieg, Noel R.; Staley, James T. (eds.) (2005). Bergey's Manual of Systematic Bacteriology, Volume Two: The Proteobacteria, Part C: The Alpha-, Be ...
'' (type family), '' Azonexaceae'' and '' Zoogloeaceae''. Morphologies include rods, curved rods, rings, spirillae and cocci. Most species are
heterotrophs A heterotroph (; ) is an organism that cannot produce its own food, instead taking nutrition from other sources of organic carbon, mainly plant or animal matter. In the food chain, heterotrophs are primary, secondary and tertiary consumers, but ...
with some photoheterotrophs and chemolithoautotrophs.


Role in disease

Some members of the ''Betaproteobacteria'' can cause disease in various
eukaryotic The eukaryotes ( ) constitute the Domain (biology), domain of Eukaryota or Eukarya, organisms whose Cell (biology), cells have a membrane-bound cell nucleus, nucleus. All animals, plants, Fungus, fungi, seaweeds, and many unicellular organisms ...
organisms, including humans. For example, ''
Neisseria gonorrhoeae ''Neisseria gonorrhoeae'', also known as ''gonococcus'' (singular) or ''gonococci'' (plural), is a species of Gram-negative diplococci bacteria first isolated by Albert Ludwig Sigesmund Neisser, Albert Neisser in 1879. An obligate human pathog ...
'' and '' N. meningitidis'' cause
gonorrhea Gonorrhoea or gonorrhea, colloquially known as the clap, is a sexually transmitted infection (STI) caused by the bacterium ''Neisseria gonorrhoeae''. Infection may involve the genitals, mouth, or rectum. Gonorrhea is spread through sexual c ...
and
meningitis Meningitis is acute or chronic inflammation of the protective membranes covering the brain and spinal cord, collectively called the meninges. The most common symptoms are fever, intense headache, vomiting and neck stiffness and occasion ...
respectively, while '' Bordetella pertussis'' causes
whooping cough Whooping cough ( or ), also known as pertussis or the 100-day cough, is a highly contagious, Vaccine-preventable diseases, vaccine-preventable Pathogenic bacteria, bacterial disease. Initial symptoms are usually similar to those of the common c ...
. Other members of the class infect plants, such as ''
Ralstonia solanacearum ''Ralstonia solanacearum'' is an aerobic non-spore-forming, Gram-negative, plant pathogenic bacterium. ''R. solanacearum'' is soil-borne and motile with a polar flagellar tuft. It colonises the xylem, causing bacterial wilt in a very wide ran ...
'' which causes bacterial wilt disease of over 250 plant species, '' Burkholderia cepacia'' which causes bulb rot in onions, and '' Xylophilus ampelinus'' which causes
necrosis Necrosis () is a form of cell injury which results in the premature death of cells in living tissue by autolysis. The term "necrosis" came about in the mid-19th century and is commonly attributed to German pathologist Rudolf Virchow, who i ...
of grapevines.


Economic importance

''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 is potentially dangerous because high ammonium content can lead to
eutrophication Eutrophication is a general term describing a process in which nutrients accumulate in a body of water, resulting in an increased growth of organisms that may deplete the oxygen in the water; ie. the process of too many plants growing on the s ...
. Biological wastewater treatment systems, as well as other biological ammonium-removing methods, depend on the metabolism of various ''Bacteria'' including members of the ''
Nitrosomonadales The ''Nitrosomonadales'' are an order of the class ''Betaproteobacteria'' in the phylum ''Pseudomonadota''.Garrity, George M.; Brenner, Don J.; Krieg, Noel R.; Staley, James T. (eds.) (2005). Bergey's Manual of Systematic Bacteriology, Volume Two ...
'' of the ''Betaproteobacteria'' that perform
nitrification ''Nitrification'' is the biological oxidation of ammonia to nitrate via the intermediary nitrite. Nitrification is an important step in the nitrogen cycle in soil. The process of complete nitrification may occur through separate organisms or ent ...
to remove excessive ammonia from wastewater. The ammonia is first oxidized into
nitrite The nitrite polyatomic ion, ion has the chemical formula . Nitrite (mostly sodium nitrite) is widely used throughout chemical and pharmaceutical industries. The nitrite anion is a pervasive intermediate in the nitrogen cycle in nature. The name ...
, further oxidized to
nitrate Nitrate is a polyatomic ion with the chemical formula . salt (chemistry), Salts containing this ion are called nitrates. Nitrates are common components of fertilizers and explosives. Almost all inorganic nitrates are solubility, soluble in wa ...
. A variety of other organisms then reduces nitrate into molecular
nitrogen Nitrogen is a chemical element; it has Symbol (chemistry), symbol N and atomic number 7. Nitrogen is a Nonmetal (chemistry), nonmetal and the lightest member of pnictogen, group 15 of the periodic table, often called the Pnictogen, pnictogens. ...
gas (
denitrification Denitrification is a microbially facilitated process where nitrate (NO3−) is reduced and ultimately produces molecular nitrogen (N2) through a series of intermediate gaseous nitrogen oxide products. Facultative anaerobic bacteria perform denitr ...
), which leaves the ecosystem and is carried into the atmosphere.


See also

* ''
Acidithiobacillia ''Acidithiobacillia'' is a class of the phylum '' Pseudomonadota'' ("Proteobacteria"). Its type order, the ''Acidithiobacillales'', was formerly classified within the '' Gammaproteobacteria'', and comprises two families of sulfur-oxidising autot ...
'' * ''
Gammaproteobacteria ''Gammaproteobacteria'' is a class of bacteria in the phylum ''Pseudomonadota'' (synonym ''Proteobacteria''). It contains about 250 genera, which makes it the most genus-rich taxon of the Prokaryotes. Several medically, ecologically, and scienti ...
'' * ''
Hydrogenophilalia The ''Hydrogenophilaceae'' are a family of the class '' Hydrogenophilalia'' in the phylum ''Pseudomonadota'' ("Proteobacteria"), with two genera – '' Hydrogenophilus'' and '' Tepidiphilus''. Like all ''Pseudomonadota'', they are Gram-negative. ...
''


References


External links

* {{Taxonbar, from=Q136674 Bacteria classes