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Burkholderia pseudomallei 01.jpg
Colonies of Burkholderia pseudomallei, one of many pathogenic Betaproteobacteria.
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Domain: Bacteria
Phylum: Proteobacteria



Betaproteobacteria are a class of gram-negative bacteria, and one of the eight classes of the phylum Proteobacteria. [1]

Gram-negative bacteria group of bacteria that do not retain the crystal violet stain used in the Gram staining method of bacterial differentiation

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 sandwiched between an inner cytoplasmic cell membrane and a bacterial outer membrane.

In biology, a phylum is a level of classification or taxonomic rank below Kingdom and above Class. Traditionally, in botany the term division has been used instead of phylum, although the International Code of Nomenclature for algae, fungi, and plants accepts the terms as equivalent. Depending on definitions, the animal kingdom Animalia or Metazoa contains approximately 35 phyla, the plant kingdom Plantae contains about 14, and the fungus kingdom Fungi contains about 8 phyla. Current research in phylogenetics is uncovering the relationships between phyla, which are contained in larger clades, like Ecdysozoa and Embryophyta.

Proteobacteria phylum of Gram-negative bacteria

Proteobacteria is a major phylum of gram-negative bacteria. They include a wide variety of pathogens, such as Escherichia, Salmonella, Vibrio, Helicobacter, Yersinia, Legionellales and many other notable genera. Others are free-living (non-parasitic) and include many of the bacteria responsible for nitrogen fixation.

The Betaproteobacteria are a class comprising over 75 genera and 400 species of bacteria. [2] Together, the Betaproteobacteria represent a broad variety of metabolic strategies and occupy diverse environments 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 [1] - many of these chemolithoautotrophic 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 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.

A genus is a taxonomic rank used in the biological classification of living and fossil organisms, as well as viruses, in biology. In the hierarchy of biological classification, genus comes above species and below family. In binomial nomenclature, the genus name forms the first part of the binomial species name for each species within the genus.

In biology, a pathogen, in the oldest and broadest sense, is anything that can produce disease. A pathogen may also be referred to as an infectious agent, or simply a germ.

Photoheterotrophs are heterotrophic phototrophs—that is, they are organisms that use light for energy, but cannot use carbon dioxide as their sole carbon source. Consequently, they use organic compounds from the environment to satisfy their carbon requirements; these compounds include carbohydrates, fatty acids, and alcohols. Examples of photoheterotrophic organisms include purple non-sulfur bacteria, green non-sulfur bacteria, and heliobacteria. Recent research has indicated that the oriental hornet and some aphids may be able to use light to supplement their energy supply.


The Betaproteobacteria are one of the eight classes that make up the "Proteobacteria". The Betaproteobacteria are most closely related to the Gammaproteobacteria , Acidithiobacillia and Hydrogenophilalia , and together they make up a taxon which has previously been called " Chromatibacteria ". [2] Four orders of Betaproteobacteria are currently recognised - the Burkholderiales , the Neisseriales , the Nitrosomonadales and the Rhodocyclales . [3] 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. [4] [5] 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 "Proteobacteria", the Hydrogenophilalia. [3] The same study also merged the former order Methylophilales into the Nitrosomonadales . [3]

Gammaproteobacteria class of bacteria

Gammaproteobacteria are a class of bacteria. Several medically, ecologically, and scientifically important groups of bacteria belong to this class. Like all Proteobacteria, the Gammaproteobacteria are Gram-negative.

Acidithiobacillia is a class of the "Proteobacteria". Its type order, the Acidithiobacillales, was formerly classified within the Gammaproteobacteria, and comprises two families of sulfur-oxidising autotrophs, the Acidithiobacillaceae and the Thermithiobacillaceae, which in turn include the genera Acidithiobacillus and Thermithiobacillus

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, and phylogenetic analyses on the basis of the 16S rRNA gene and 53 ribosomal protein sequences concatenated using the rMLST platform for multilocus sequence typing.

The four orders of the Betaproteobactera are sub-divided into families:
Burkholderiales (type order) comprises the families Burkholderiacae (type family), Alcaliginaceae , Commamonadaceae , Oxalobacteraceae and Sutterellaceae . The order Burkholderiales comprises a range of morphologies, including rods, curved rods, cocci, spirillae and multicellular 'tablets'. Both heterotrophs and photoheterotrophs are found along with some facultative autotrophs. [3]
Neisseriales comprises the families Neisseriaceae (type family) and Chromobacteriaceae . The order Neisseriales comprises morphologies including cocci, curved rods, spirillae, rods, multicellular ribbons and filaments. Most organisms are heterotrophs with some facultative methylotrophs and chemolithoheterotrophs. [3]
Nitrosomonadales comprises the families Nitrosomonadaceae (type family), Methylophilacae , Thiobacillaceae , Sterolibacteriacae , Spirillaceae and Gallionellaceae . The order comprises morphologies including rods, spirillae and curved rods. Most organisms are chemolithoautotrophs with some methylotrophs and heterotrophs [3]
Rhodocyclales 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 with some photoheterotrophs and chemolithoautotrophs. [3]

Burkholderiales order of bacteria

The Burkholderiales are an order of Proteobacteria. Like all Proteobacteria, 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, non-pathogenic Paraburkholderia, Caballeronia, Polaromonas, Thiomonas, Collimonas, Hydrogenophaga, Sphaerotilus, Variovorax, Acidovorax, Rubrivivax and Rhodoferax, and Herbaspirillum.

The Oxalobacteraceae are a family of bacteria, included in the order Burkholderiales. Like all Proteobacteria, Oxalobacteraceae are Gram-negative. The family includes strict aerobes, strict anaerobes, and nitrogen-fixing (diazotrophic) members. The cells are curved, vibroid, or straight rod-shaped.

The Sutterellaceae are a family of the Betaproteobacteria. Cells of Sutterellaceae are Gram-negative, oxidase- and catalase-negative, and grow under microaerophilic or anaerobic atmospheres.

Role in disease

Some members of the Betaproteobacteria can cause disease in various eukaryotic organisms, including in humans, such as members of the genus Neisseria : N. gonorrhoeae and N. meninngitides being primary examples, which cause gonorrhea and meningitis respectively, as well as Bordetella pertussis which causes whooping cough. Other members of the class can infect plants, such as Burkholderia cepacia which causes bulb rot in onions as well as Xylophilus ampelinus which causes necrosis of grapevines. [6]

Eukaryote taxonomic group whose members have complex structures enclosed within membranes

Eukaryotes are organisms whose cells have a nucleus enclosed within membranes, unlike prokaryotes, which have no membrane-bound organelles. Eukaryotes belong to the domain Eukaryota or Eukarya. Their name comes from the Greek εὖ and κάρυον. Eukaryotic cells also contain other membrane-bound organelles such as mitochondria and the Golgi apparatus, and in addition, some cells of plants and algae contain chloroplasts. Unlike unicellular archaea and bacteria, eukaryotes may also be multicellular and include organisms consisting of many cell types forming different kinds of tissue. Animals and plants are the most familiar eukaryotes.

<i>Neisseria</i> genus of bacteria

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. Most gonoccocal infections are asymptomatic and self-resolving, and epidemic strains of the meningococcus may be carried in >95% of a population where systemic disease occurs at <1% prevalence.

<i>Neisseria gonorrhoeae</i> species of bacterium

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 gonorrhea as well as other forms of gonococcal disease including disseminated gonococcemia, septic arthritis, and gonococcal ophthalmia neonatorum.

Economic Importance

Various human activities, such as fertilizer production and chemical plant usage, release significant amounts of ammonium ions into rivers and oceans. [7] [8] Ammonium buildup in aquatic environments is potentially dangerous because high ammonium content can lead to eutrophication. [7] 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 undergo nitrification and a wide range of organisms capable of denitrification to remove excessive ammonia from wastewater by first oxidation into nitrate and then nitrite and then reduction into molecular nitrogen gas, which leaves the ecosystem and is carried into the atmosphere. [8] [9]

Eutrophication ecosystem response to the addition of substances

Eutrophication, or hypertrophication, is when a body of water becomes overly enriched with minerals and nutrients which induce excessive growth of plants and algae. This process may result in oxygen depletion of the water body. One example is an "algal bloom" or great increase of phytoplankton in a water body as a response to increased levels of nutrients. Eutrophication is often induced by the discharge of nitrate or phosphate-containing detergents, fertilizers, or sewage into an aquatic system.

Nitrosomonadales order of bacteria

The Nitrosomonadales are an order of the class Betaproteobacteria in the phylum "Proteobacteria". Like all members of their class, they are Gram-negative.

Nitrification biological oxidation of ammonia or ammonium to nitrite followed by the oxidation of the nitrite to nitrate

Nitrification is the biological oxidation of ammonia or ammonium to nitrite followed by the oxidation of the nitrite to nitrate. The transformation of ammonia to nitrite is usually the rate limiting step of nitrification. Nitrification is an important step in the nitrogen cycle in soil. Nitrification is an aerobic process performed by small groups of autotrophic bacteria and archaea. This process was discovered by the Russian microbiologist Sergei Winogradsky.

See also

Related Research Articles

The Rhodocyclaceae are a family of gram-negative bacteria. They are given their own order in the beta subgroup of Proteobacteria, and include many genera previously assigned to the family Pseudomonadaceae.

Rhodocyclales order of bacteria

The Rhodocyclales are an order of the class Betaproteobacteria in the phylum "Proteobacteria". Following a major reclassification of the class in 2017, the previously monofamilial order was split into three families:

The Hydrogenophilaceae are a family of the Hydrogenophilalia, with two genera – Hydrogenophilus and Tepidiphilus. Like all "Proteobacteria", they are Gram-negative. All known species are thermophilic, growing around 50 °C and using molecular hydrogen or organic molecules as their source of electrons to support growth - some species are autotrophs.

Thiobacillus is a genus of Gram-negative Betaproteobacteria. Thiobacilus thioparus is the type species of the genus, and the type strain thereof is the StarkeyT strain, isolated by Robert Starkey in the 1930s from a field at Rutgers University in the United States of America. While over 30 "species" have been named in this genus since it was defined by Martinus Beijerinck in 1904, most names were never validly or effectively published. The remainder were either reclassified into Paracoccus, Starkeya ; Sulfuriferula, Annwoodia, Thiomonas ; Halothiobacillus, Guyparkeria, or Thermithiobacillus or Acidithiobacillus. The very loosely defined "species" Thiobacillus trautweinii was where sulfur oxidising heterotrophs and chemolithoheterotrophs were assigned in the 1910-1960s era, most of which were probably Pseudomonas species. Many species named in this genus were never deposited in service collections and have been lost.

The Acidithiobacillales are an order of bacteria within the class Acidithiobacillia and comprises the genera Acidithiobacillus and Thermithiobacillus. Originally, both were included in the genus Thiobacillus, but they are not related to the type species, which belongs to the Betaproteobacteria.

<i>Brocadia anammoxidans</i> species of bacterium

"Candidatus Brocadia anammoxidans" is a bacterial member of the order Planctomycetes and therefore lacks peptidoglycan in its cell wall, and has a compartmentalized cytoplasm.

Microbial metabolism is the means by which a microbe obtains the energy and nutrients it needs to live and reproduce. Microbes use many different types of metabolic strategies and species can often be differentiated from each other based on metabolic characteristics. The specific metabolic properties of a microbe are the major factors in determining that microbe's ecological niche, and often allow for that microbe to be useful in industrial processes or responsible for biogeochemical cycles.

Thauera is a genus of Gram-negative bacteria in the family Zoogloeaceae of the order Rhodocyclales of the Betaproteobacteria. The genus is named for the German microbiologist Rudolf Thauer. Most species of this genus are motile by flagella and are mostly rod-shaped. The species occur in wet soil and polluted freshwater.

Spirillaceae family of bacteria

Spirillaceae is a family in the order Nitrosomonadales in the class Betaproteobacteria of the bacteria.

Dechloromonas is a genus in the phylum Proteobacteria (Bacteria).

Azoarcus is a genus of nitrogen-fixing bacteria. Species in this genus are usually found in contaminated water, as they are involved in the degradation of some contaminants, commonly inhabiting soil. These bacteria have also been found growing in the endophytic compartment of some rice species and other grasses. The genus is within the family Zoogloeaceae in the Rhodocyclales of the Betaproteobacteria.

Azonexus is a genus of gram-negative, non-spore-forming, highly motile bacteria that is the type genus of the family Azonexaceae which is in the order Rhodocyclales of the class Betaproteobacteria.

Azovibrio is a genus of bacteria from the order Rhodocyclales which belongs to the class of Betaproteobacteria, but the family to which it belongs is uncertain since it falls in between the Zoogloeaceae and the Rhodocyclaceae. Up to now there is only on species known.

<i>Zoogloea</i> genus of bacteria

Zoogloea is a genus of gram-negative, aerobic, rod-shaped bacteria from the family of Zoogloeaceae in the Rhodocyclales of the class Betaproteobacteria.

Dissimilatory nitrate reduction to ammonium (DNRA), also known as nitrate/nitrite ammonification, is the result of anaerobic respiration by chemoorganoheterotrophic microbes using nitrate (NO3) as an electron acceptor for respiration. In anaerobic conditions microbes which undertake DNRA oxidise organic matter and use nitrate (rather than oxygen) as an electron acceptor, reducing it to nitrite, then ammonium (NO3→NO2→NH4+).

The genus Annwoodia was named in 2017 to circumscribe an organism previously described as a member of the genus Thiobacillus, Thiobacillus aquaesulis - the type and only species is Annwoodia aquaesulis, which was isolated from the geothermal waters of the Roman Baths in the city of Bath in the United Kingdom by Ann P. Wood and Donovan P. Kelly of the University of Warwick - the genus was subsequently named to honour Wood's contribution to microbiology. The genus falls within the family Thiobacillaceae along with Thiobacillus and Sulfuritortus, both of which comprise autotrophic organisms dependent on thiosulfate, other sulfur oxyanions and sulfide as electron donors for chemolithoheterotrophic growth. Whilst Annwoodia spp. and Sulfuritortus spp. are thermophilic, Thiobacillus spp. are mesophilic.


  1. 1 2 Slonczewski JL, Foster JW (2014). Microbiology: An Evolving Science (3rd ed.). W. W. Norton & Company. pp. 742–3. ISBN   9780393123678.
  2. 1 2 Dworkin M, Falkow S, Rosenberg E, Schleifer KH, Stackebrandt E, eds. (2006). The Prokaryotes, Volume 5 - Proteobacteria: Alpha and Beta Subclasses (3rd ed.). Springer. pp. 15–18. doi:10.1007/0-387-30745-1. ISBN   9780387254951.
  3. 1 2 3 4 5 6 7 Boden 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 Hydrogenophilales to the Nitrosomonadales, proposal of Hydrogenophilalia class. nov. within the Proteobacteria, and four new families within the orders Nitrosomonadales and Rhodocyclales". International Journal of Systematic and Evolutionary Microbiology. 67 (5): 1191–1205. doi:10.1099/ijsem.0.001927. PMID   28581923.
  4. J.P. Euzéby. "Betaproteobacteria". List of Prokaryotic names with Standing in Nomenclature (LPSN). Retrieved 21 May 2017.
  5. Horn M, Fritsche TR, Linner T, Gautom RK, Harzenetter MD, Wagner M (2002). "Obligate bacterial endosymbionts of Acanthamoeba spp. related to the beta-Proteobacteria: proposal of " Candidatus Procabacter acanthamoebae" gen. nov., sp. nov". International Journal of Systematic and Evolutionary Microbiology. 52 (2): 599–605. doi:10.1099/00207713-52-2-599. PMID   11931173.
  6. Dworkin M, Falkow S, Rosenberg E, Schleifer KH, Stackebrandt E, eds. (2006). The Prokaryotes, Volume 5 - Proteobacteria: Alpha and Beta Subclasses (3rd ed.). Springer. p. 11. doi:10.1007/0-387-30745-1. ISBN   9780387254951.
  7. 1 2 Bonnet, C.; Volat, B.; Bardin, R.; Degranges, V.; Montuelle, B. (March 1997). "Use of immunofluorescence technique for studying a Nitrobacter population from wastewater treatment plant following discharge in river sediments: First experimental data". Water Research. 31 (3): 661–664. doi:10.1016/S0043-1354(96)00094-2.
  8. 1 2 Prasad, V. S. R. K.; Siva Prasad, V. G. S. G.; Sridevi, Venigalla; Sudarsan, K. G. (September 2015). "Biodegradation of Ammoniacal Nitrogen to Nitrite in an Industrial Effluent using Nitrosomonas species: First stage in Nitrification". Journal of Chemical, Biological and Physical Sciences. 5 (4): 4733–4740.
  9. Cydzik-Kwiatkowska, Agnieszka; Zielińska, Magdalena (Mar 2016). "Bacterial communities in full-scale wastewater treatment systems". World J Microbiol Biotechnol. 32 (66): 66. doi:10.1007/s11274-016-2012-9. PMC   4773473 . PMID   26931606.