{{Short description|Class of bacteria}} {{Automatic taxobox | image = Burkholderia pseudomallei 01.jpg | image_caption = Colonies of ''Burkholderia pseudomallei'', one of many pathogenic Betaproteobacteria. | taxon = Betaproteobacteria | authority = | subdivision_ranks = Orders | subdivision = Burkholderiales<br /> Ferritrophicales<br /> Ferrovales<br /> Neisseriales<br /> Nitrosomonadales <br /> Procabacteriales<br /> Rhodocyclales }}
'''''Betaproteobacteria''''' are a class of Gram-negative bacteria, and one of the six classes of the phylum ''Pseudomonadota'' (synonym Proteobacteria).<ref name="Slonczewski">{{cite book|title=Microbiology: An Evolving Science|vauthors=Slonczewski JL, Foster JW|date=2014|publisher=W. W. Norton & Company|isbn=978-0-393-12367-8|edition=3rd|pages=742–3}}</ref>
== Metabolism == The ''Betaproteobacteria'' comprise over 75 genera and 400 species.<ref name="ProkaryotesIntro">{{cite book|title=The Prokaryotes, Volume 5 - Proteobacteria: Alpha and Beta Subclasses |veditors=Dworkin M, Falkow S, Rosenberg E, Schleifer KH, Stackebrandt E |edition=3rd |publisher=Springer |date=2006 |isbn=978-0-387-25495-1 |doi=10.1007/0-387-30745-1 |pages=15–18}}</ref> 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 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<ref name="Slonczewski" /> — many of these chemolithoautotrophic.
''Betaproteobacteria'' are economically important, with roles in maintaining soil pH and in elementary cycling. Some economically important members of 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 the presence of leguminous plants.
==Phylogeny== 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".<ref name=ProkaryotesIntro/>
Four orders of ''Betaproteobacteria'' are currently recognised — the ''Burkholderiales'', the ''Neisseriales'', the ''Nitrosomonadales'' and the ''Rhodocyclales''.<ref name="Boden2017" /> 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.<ref name="LPSN">{{cite web |author = J.P. Euzéby | url=https://www.bacterio.net/-classifphyla.html#betaproteobacteria |title=Betaproteobacteria | access-date=21 May 2017 |publisher=List of Prokaryotic names with Standing in Nomenclature (LPSN)}}</ref><ref name="Horn2002">{{cite journal | vauthors = Horn M, Fritsche TR, Linner T, Gautom RK, Harzenetter MD, Wagner M | title = Obligate bacterial endosymbionts of ''Acanthamoeba'' spp. related to the beta-Proteobacteria: proposal of " ''Candidatus'' Procabacter acanthamoebae" gen. nov., sp. nov | journal = International Journal of Systematic and Evolutionary Microbiology | volume = 52 | issue = 2 | pages = 599–605 | year = 2002 | pmid = 11931173 | doi = 10.1099/00207713-52-2-599| doi-access = free }}</ref>
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 system) was published in 2017, that removed the order ''Hydrogenophilales'' from the class and into a novel class of the "Pseudomonadota", the ''Hydrogenophilalia''.<ref name="Boden2017">{{cite journal | vauthors = Boden R, Hutt LP, Rae AW | title = Reclassification of ''Thiobacillus aquaesulis'' (Wood & Kelly, 1995) as ''Annwoodia aquaesulis'' gen. nov., comb. nov., transfer of ''Thiobacillus'' (Beijerinck, 1904) from the ''Hydrogenophilales'' to the ''Nitrosomonadales'', proposal of ''Hydrogenophilalia'' class. nov. within the '''Proteobacteria''', and four new families within the orders ''Nitrosomonadales'' and ''Rhodocyclales''. | journal = International Journal of Systematic and Evolutionary Microbiology | volume = 67 | issue = 5 | pages = 1191–1205 | year = 2017 | pmid = 28581923 | doi = 10.1099/ijsem.0.001927| hdl = 10026.1/8740 | doi-access = free | hdl-access = free }}</ref> The same study also merged the former order ''Methylophilales'' into the ''Nitrosomonadales''.<ref name="Boden2017" />
The four orders of the ''Betaproteobacteria'' are: * '''''Burkholderiales''''' (type order) comprises the families ''Burkholderiacae'' (type family), ''Alcaliginaceae'', ''Comamonadaceae'', ''Oxalobacteraceae'' and ''Sutterellaceae''. They exhibit a range of morphologies, including rods, curved rods, cocci, spirillae and multicellular 'tablets'. Both heterotrophs and photoheterotrophs are found along with some facultative autotrophs.<ref name="Boden2017" /> * '''''Neisseriales''''' comprises the families ''Neisseriaceae'' (type family) and ''Chromobacteriaceae''. Their morphologies include cocci, curved rods, spirillae, rods, multicellular ribbons and filaments. Most are heterotrophs with some facultative methylotrophs and chemolithoheterotrophs.<ref name="Boden2017" /> * '''''Nitrosomonadales''''' comprises the families ''Nitrosomonadaceae'' (type family), ''Methylophilacae'', ''Thiobacillaceae'', ''Sterolibacteriacae'', ''Spirillaceae'' and ''Gallionellaceae''. Their morphologies include rods, spirillae and curved rods. Most are chemolithoautotrophs with some methylotrophs and heterotrophs<ref name="Boden2017" /> * '''''Rhodocyclales''''' comprises the families ''Rhodocyclaceae'' (type family), ''Azonexaceae'', and ''Zoogloeaceae''. Morphologies include rods, curved rods, rings, spirillae and cocci. Most species are heterotrophs with some photoheterotrophs and chemolithoautotrophs.<ref name="Boden2017" />
==Role in disease== Some members of the ''Betaproteobacteria'' can cause disease in various eukaryotic organisms, including humans. For example, ''Neisseria gonorrhoeae'' and ''Neisseria 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.<ref name=Prokaryotes11>{{cite book|title=The Prokaryotes, Volume 5 - Proteobacteria: Alpha and Beta Subclasses |veditors=Dworkin M, Falkow S, Rosenberg E, Schleifer KH, Stackebrandt E |edition=3rd |publisher=Springer |date=2006 |isbn=978-0-387-25495-1 |doi=10.1007/0-387-30745-1 |page=11}}</ref>
==Economic importance== ''Betaproteobacteria'' play an important role in denitrification, removal of phosphorus, and xenobiotic degradation from waste.<ref>{{Cite journal |last1=Marathe |first1=Nachiket P. |last2=Shetty |first2=Sudarshan A. |last3=Shouche |first3=Yogesh S. |last4=Larsson |first4=D. G. Joakim |date=2016-11-03 |title=Limited Bacterial Diversity within a Treatment Plant Receiving Antibiotic-Containing Waste from Bulk Drug Production |journal=PLOS ONE |volume=11 |issue=11 |article-number=e0165914 |doi=10.1371/journal.pone.0165914 |issn=1932-6203 |pmc=5094703 |pmid=27812209 |doi-access=free}}</ref> Various human activities, such as fertilizer production and chemical plant usage, release significant amounts of ammonium ions into rivers and oceans.<ref name="Bonnet et al">{{cite journal|last1=Bonnet|first1=C.|last2=Volat|first2=B.|last3=Bardin|first3=R.|last4=Degranges|first4=V.|last5=Montuelle|first5=B.|title=Use of immunofluorescence technique for studying a Nitrobacter population from wastewater treatment plant following discharge in river sediments: First experimental data|journal=Water Research|date=March 1997|volume=31|issue=3|pages=661–664|doi=10.1016/S0043-1354(96)00094-2}}</ref> Ammonium buildup in aquatic environments is potentially dangerous because high ammonium content can lead to eutrophication.<ref name="Bonnet et al"/> 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 the ecosystem and is carried into the atmosphere.<ref name="Agnieszka et al">{{cite journal|last1=Cydzik-Kwiatkowska|first1=Agnieszka|last2=Zielińska|first2=Magdalena|title=Bacterial communities in full-scale wastewater treatment systems|journal= World Journal of Microbiology and Biotechnology|date=Mar 2016|volume=32|issue=66|page=66|doi=10.1007/s11274-016-2012-9|pmid=26931606|pmc=4773473}}</ref>
==See also== * ''Acidithiobacillia'' * ''Gammaproteobacteria'' * ''Hydrogenophilalia''
==References== {{Reflist|2}}
==External links== * {{MeshName|Betaproteobacteria}}
{{Bacteria classification}} {{Gram-negative bacterial diseases}} {{Taxonbar|from=Q136674}}
Category:Betaproteobacteria Category:Bacteria classes