Betaproteobacteria are a class of
Gram-negative bacteria
Gram-negative bacteria are bacteria that do not retain the crystal violet stain used in the Gram staining method of bacterial differentiation. They are characterized by their cell envelopes, which are composed of a thin peptidoglycan cell wall ...
, and one of the eight classes of the
phylum Pseudomonadota (synonym Proteobacteria).
The ''Betaproteobacteria'' are a class comprising over 75
genera and 400 species of bacteria.
Together, the ''Betaproteobacteria'' represent a broad variety of metabolic strategies and occupy diverse environments from obligate
pathogen
In biology, a pathogen ( el, πάθος, "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 ...
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 ('' 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 source. Con ...
ic, deriving energy from light and carbon from organocarbon sources. Other genera are
autotroph
An autotroph or primary producer is an organism that produces complex organic compounds (such as carbohydrates, fats, and proteins) using carbon from simple substances such as carbon dioxide,Morris, J. et al. (2019). "Biology: How Life Wo ...
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 biochem ...
or
carbon dioxide
Carbon dioxide ( chemical formula ) is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature. In the air, carbon dioxide is trans ...
and their electrons from reduced
inorganic
In chemistry, an inorganic compound is typically a chemical compound that lacks carbon–hydrogen bonds, that is, a compound that is not an organic compound. The study of inorganic compounds is a subfield of chemistry known as ''inorganic chemist ...
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 conve ...
s such as
nitrite,
ammonium,
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[ — many of these ]chemolithoautotrophic A lithoautotroph is an organism which 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 while ...
. ''Betaproteobacteria'' are economically important, with roles in maintaining soil pH and in elementary cycling. Other economically important members of the ''Betaproteobacteria'' are able to use nitrate as their terminal electron acceptor
An electron acceptor is a chemical entity that accepts electrons transferred to it from another compound. It is an oxidizing agent that, by virtue of its accepting electrons, is itself reduced in the process. Electron acceptors are sometimes mista ...
and can be used industrially to remove nitrate from wastewater
Wastewater 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 domestic, industrial ...
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 bacteria and archaea that fix gaseous nitrogen in the atmosphere into a more usable form such as ammonia.
A diazotroph is a microorganism that is able to grow without external sources of fixed nitrogen. Examples of organisms that ...
s, meaning that they can fix molecular nitrogen
Nitrogen is the chemical element with the symbol N and atomic number 7. Nitrogen is a nonmetal and the lightest member of group 15 of the periodic table, often called the pnictogens. It is a common element in the universe, estimated at se ...
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 the presence of leguminous plants.
Phylogeny
The ''Betaproteobacteria'' are one of the eight classes that make up the "Proteobacteria". The ''Betaproteobacteria'' are most closely related to the '' Gammaproteobacteria'', ''Acidithiobacillia
Acidithiobacillia is a class of the "''Pseudomonadota''". Its type order, the '' Acidithiobacillales'', was formerly classified within the ''Gammaproteobacteria'', and comprises two families of sulfur-oxidising autotroph
An autotroph or prim ...
'' and ''Hydrogenophilalia
The class Hydrogenophilalia in the ''Bacteria'' was circumscribed in 2017 when it was demonstrated that the order ''Hydrogenophilales'' was distinct from the ''Betaproteobacteria'' on the basis of physiology, biochemistry, fatty acid profiles, an ...
'', and together they make up a taxon
In biology, a taxon ( back-formation from '' taxonomy''; plural 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 n ...
which has previously been called "'' Chromatibacteria''".[ Four orders of ''Betaproteobacteria'' are currently recognised — the '']Burkholderiales
The Burkholderiales are an order of Pseudomonadota.George M. Garrity: ''Bergey's Manual of Systematic Bacteriology''. 2. Auflage. Springer, New York, 2005, Vol. 2: ''The Proteobacteria Part C: The Alpha-, Beta-, Delta-, and Epsilonproteabacteria' ...
'', the ''Neisseriales
The Neisseriaceae are a family of Pseudomonadota, within the ''Neisseriales'' order. While many organisms in the family are mammalian commensals or part of the normal Flora (microbiology), flora, the genus ''Neisseria'' includes two important hum ...
'', the ''Nitrosomonadales
The NitrosomonadalesBoden, R; Hutt, LP, Rae AW (2017) Reclassification of ''Thiobacillus aquaesulis'' (Wood & Kelly, 1995) as ''Annwoodia aquaesulis'' gen. nov., comb. nov., transfer of ''Thiobacillus'' (Beijerinck, 1904) from the ''Hydrogenophil ...
'' and the ''Rhodocyclales
The ''Rhodocyclales'' 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 Tw ...
''. The name "''Procabacteriales
"Procabacteriaceae" is a ''Candidatus'' family of uncultivated Gram-negative Betaproteobacteria. The sole genus, ''" Procabacter"'', was identified as an obligate endosymbiont of ''Acanthamoeba
''Acanthamoeba'' is a genus of amoebae that ar ...
''" was also proposed for an order of endosymbiont
An ''endosymbiont'' or ''endobiont'' is any organism that lives within the body or cells of another organism most often, though not always, in a mutualistic relationship.
(The term endosymbiosis is from the Greek: ἔνδον ''endon'' "within ...
s of ''Acanthamoeba
''Acanthamoeba'' is a genus of amoebae that are commonly recovered from soil, fresh water, and other habitats.
''Acanthamoeba'' has two evolutive forms, the metabolically active trophozoite and a dormant, stress-resistant cyst. Trophozoites are ...
'', 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 Hydrogenophilalia, with two genera – '' Hydrogenophilus'' and '' Tepidiphilus''. Like all ''Pseudomonadota'', they are Gram-negative. All known species are thermophilic, growing around 50 °C and ...
from the class and into a novel class of the " Pseudomonadota", the Hydrogenophilalia
The class Hydrogenophilalia in the ''Bacteria'' was circumscribed in 2017 when it was demonstrated that the order ''Hydrogenophilales'' was distinct from the ''Betaproteobacteria'' on the basis of physiology, biochemistry, fatty acid profiles, an ...
. The same study also merged the former order '' Methylophilales'' into the ''Nitrosomonadales
The NitrosomonadalesBoden, R; Hutt, LP, Rae AW (2017) Reclassification of ''Thiobacillus aquaesulis'' (Wood & Kelly, 1995) as ''Annwoodia aquaesulis'' gen. nov., comb. nov., transfer of ''Thiobacillus'' (Beijerinck, 1904) from the ''Hydrogenophil ...
''.
The four orders of the ''Betaproteobacteria'' are sub-divided into families:
''Burkholderiales
The Burkholderiales are an order of Pseudomonadota.George M. Garrity: ''Bergey's Manual of Systematic Bacteriology''. 2. Auflage. Springer, New York, 2005, Vol. 2: ''The Proteobacteria Part C: The Alpha-, Beta-, Delta-, and Epsilonproteabacteria' ...
'' (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
Gram-negative bacteria are bacteria that do not retain the crystal violet stain used in the Gra ...
'' and ''Sutterellaceae
The Sutterellaceae are a family of the Betaproteobacteria. Cells of Sutterellaceae are Gram-negative, oxidase- and catalase-negative, and grow under microaerophilic or anaerobic
Anaerobic means "living, active, occurring, or existing in the abs ...
''.
The order ''Burkholderiales
The Burkholderiales are an order of Pseudomonadota.George M. Garrity: ''Bergey's Manual of Systematic Bacteriology''. 2. Auflage. Springer, New York, 2005, Vol. 2: ''The Proteobacteria Part C: The Alpha-, Beta-, Delta-, and Epsilonproteabacteria' ...
'' comprises 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 or primary producer is an organism that produces complex organic compounds (such as carbohydrates, fats, and proteins) using carbon from simple substances such as carbon dioxide,Morris, J. et al. (2019). "Biology: How Life Works", ...
.
''Neisseriales
The Neisseriaceae are a family of Pseudomonadota, within the ''Neisseriales'' order. While many organisms in the family are mammalian commensals or part of the normal Flora (microbiology), flora, the genus ''Neisseria'' includes two important hum ...
'' comprises the families ''Neisseriaceae
The Neisseriaceae are a family of Pseudomonadota, within the ''Neisseriales'' order. While many organisms in the family are mammalian commensals or part of the normal flora, the genus ''Neisseria'' includes two important human pathogens, specifi ...
'' (type family) and '' Chromobacteriaceae''. The order ''Neisseriales
The Neisseriaceae are a family of Pseudomonadota, within the ''Neisseriales'' order. While many organisms in the family are mammalian commensals or part of the normal Flora (microbiology), flora, the genus ''Neisseria'' includes two important hum ...
'' comprises morphologies including cocci, curved rods, spirillae, rods, multicellular ribbons and filaments. Most organisms 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 NitrosomonadalesBoden, R; Hutt, LP, Rae AW (2017) Reclassification of ''Thiobacillus aquaesulis'' (Wood & Kelly, 1995) as ''Annwoodia aquaesulis'' gen. nov., comb. nov., transfer of ''Thiobacillus'' (Beijerinck, 1904) from the ''Hydrogenophil ...
'' comprises the families '' Nitrosomonadaceae'' (type family), '' Methylophilacae'', '' Thiobacillaceae'', '' Sterolibacteriacae'', ''Spirillaceae
Spirillaceae is a family in the order '' Nitrosomonadales'' in the class ''Betaproteobacteria'' of the bacteria.
Only one genus, ''Spirillum
''Spirillum'' is a genus of Gram-negative bacteria in the family '' Spirillaceae'' of the '' Nitros ...
'' and '' Gallionellaceae''. The order comprises morphologies including rods, spirillae and curved rods. Most organisms 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''".Garrity, George M.; Brenner, Don J.; Krieg, Noel R.; Staley, James T. (eds.) (2005). Bergey's Manual of Systematic Bacteriology, Volume Tw ...
'' comprises the families '' Rhodocyclaceae'' (type family), '' Azonexaceae'' and '' Zoogloeaceae''. Morphologies include rods, curved rods, rings, spirillae and cocci. Most species in this order 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
Eukaryotes () are organisms whose Cell (biology), cells have a cell nucleus, nucleus. All animals, plants, fungi, and many unicellular organisms, are Eukaryotes. They belong to the group of organisms Eukaryota or Eukarya, which is one of the ...
organisms, including in humans, such as members of the genus ''Neisseria
''Neisseria'' is a large genus of bacteria that colonize the mucosal surfaces of many animals. Of the 11 species that colonize humans, only two are pathogens, '' N. meningitidis'' and ''N. gonorrhoeae''.
''Neisseria'' species are Gram-negativ ...
'': ''N. gonorrhoeae
''Neisseria gonorrhoeae'', also known as ''gonococcus'' (singular), or ''gonococci'' (plural), is a species of Gram-negative diplococci bacteria isolated by Albert Neisser in 1879. It causes the sexually transmitted genitourinary infection gon ...
'' and '' N. meningitidis'' being primary examples, which cause gonorrhea
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. Infected men may experience pain or burning with u ...
and meningitis respectively, as well as ''Bordetella pertussis
''Bordetella pertussis'' is a Gram-negative, aerobic, pathogenic, encapsulated coccobacillus of the genus ''Bordetella'', and the causative agent of pertussis or whooping cough. Like '' B. bronchiseptica'', ''B. pertussis'' is motile and expre ...
'' which causes whooping cough
Whooping cough, also known as pertussis or the 100-day cough, is a highly contagious bacterial disease. Initial symptoms are usually similar to those of the common cold with a runny nose, fever, and mild cough, but these are followed by two or t ...
. Other members of the class can 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 rang ...
'' which causes bacterial wilt disease of over 250 plant species, '' Burkholderia cepacia'' which causes bulb rot in onions as well as '' Xylophilus ampelinus'' which causes necrosis of grapevines. Betaproteobacteria is known to play an important role in denitrification, removal of phosphorus and xenobiotic degradation from the waste
Economic Importance
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 the process by which an entire body of water, or parts of it, becomes progressively enriched with minerals and nutrients, particularly nitrogen and phosphorus. It has also been defined as "nutrient-induced increase in phytopla ...
. 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 NitrosomonadalesBoden, R; Hutt, LP, Rae AW (2017) Reclassification of ''Thiobacillus aquaesulis'' (Wood & Kelly, 1995) as ''Annwoodia aquaesulis'' gen. nov., comb. nov., transfer of ''Thiobacillus'' (Beijerinck, 1904) from the ''Hydrogenophil ...
'' of the ''Betaproteobacteria'' that undergo nitrification
''Nitrification'' is the biological oxidation of ammonia to nitrite followed by the oxidation of the nitrite to nitrate occurring through separate organisms or direct ammonia oxidation to nitrate in comammox bacteria. The transformation of am ...
and a wide range of organisms capable of 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 ...
to remove excessive ammonia from wastewater by first oxidation into nitrate and then nitrite and then reduction into molecular nitrogen
Nitrogen is the chemical element with the symbol N and atomic number 7. Nitrogen is a nonmetal and the lightest member of group 15 of the periodic table, often called the pnictogens. It is a common element in the universe, estimated at se ...
gas, which leaves the ecosystem and is carried into the atmosphere.
See also
* ''Acidithiobacillia
Acidithiobacillia is a class of the "''Pseudomonadota''". Its type order, the '' Acidithiobacillales'', was formerly classified within the ''Gammaproteobacteria'', and comprises two families of sulfur-oxidising autotroph
An autotroph or prim ...
''
* '' Gammaproteobacteria''
* ''Hydrogenophilalia
The class Hydrogenophilalia in the ''Bacteria'' was circumscribed in 2017 when it was demonstrated that the order ''Hydrogenophilales'' was distinct from the ''Betaproteobacteria'' on the basis of physiology, biochemistry, fatty acid profiles, an ...
''
References
External links
*
{{Taxonbar, from=Q136674
Bacteria classes