Pseudomonadota is a major phylum of Gram-negative bacteria. The renaming of several prokaryote phyla in 2021, including Pseudomonadota, remains controversial among microbiologists, many of whom continue to use the earlier name Proteobacteria, of long standing in the literature. The phylum Proteobacteria includes a wide variety of pathogenic genera, such as Escherichia, Salmonella, Vibrio, Yersinia, Legionella, and many others. Others are free-living (non-parasitic) and include many of the bacteria responsible for nitrogen fixation.
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 denitrification as a type of respiration that reduces oxidized forms of nitrogen in response to the oxidation of an electron donor such as organic matter. The preferred nitrogen electron acceptors in order of most to least thermodynamically favorable include nitrate (NO3−), nitrite (NO2−), nitric oxide (NO), nitrous oxide (N2O) finally resulting in the production of dinitrogen (N2) completing the nitrogen cycle. Denitrifying microbes require a very low oxygen concentration of less than 10%, as well as organic C for energy. Since denitrification can remove NO3−, reducing its leaching to groundwater, it can be strategically used to treat sewage or animal residues of high nitrogen content. Denitrification can leak N2O, which is an ozone-depleting substance and a greenhouse gas that can have a considerable influence on global warming.
The Rhodocyclaceae are a family of gram-negative bacteria. They are given their own order in the beta subgroup of Pseudomonadota, and include many genera previously assigned to the family Pseudomonadaceae.
The Rhodocyclales are an order of the class Betaproteobacteria in the phylum Pseudomonadota ("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 class Hydrogenophilalia in the phylum Pseudomonadota ("Proteobacteria"), with two genera – Hydrogenophilus and Tepidiphilus. Like all Pseudomonadota, they are Gram-negative. All known species are thermophilic, growing around 50 °C, and use 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. Thiobacillus 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.
Nitrobacter is a genus comprising rod-shaped, gram-negative, and chemoautotrophic bacteria. The name Nitrobacter derives from the Latin neuter gender noun nitrum, nitri, alkalis; the Ancient Greek noun βακτηρία, βακτηρίᾱς, rod. They are non-motile and reproduce via budding or binary fission. Nitrobacter cells are obligate aerobes and have a doubling time of about 13 hours.
Gammaproteobacteria is a class of bacteria in the phylum Pseudomonadota. It contains about 250 genera, which makes it the most genus-rich taxon of the Prokaryotes. Several medically, ecologically, and scientifically important groups of bacteria belong to this class. All members of this class are Gram-negative. It is the most phylogenetically and physiologically diverse class of the Pseudomonadota.
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 is a family in the order Nitrosomonadales in the class Betaproteobacteria of the bacteria.
Dechloromonas is a genus in the phylum Pseudomonadota (Bacteria).
Azoarcus indigens is a species of bacteria. It is a nitrogen-fixing bacteria associated with roots of Leptochloa fusca . Its cells are yellow-pigmented, straight to curved, gram-negative rods. Its type strain is VB32.
Azoarcus communis is a species of bacteria. It is a nitrogen-fixing bacteria. Its cells are yellow-pigmented, straight to curved, gram-negative rods. Its type strain is LMG 5514.
Azoarcus olearius is a species of bacteria. It is a nitrogen-fixing bacteria. Its cells are Gram-negative, motile and rod-shaped, surrounded by a thin capsule. Its type strain is DQS-4T.
Azoarcus tolulyticus is a species of bacteria. It is a nitrogen-fixing bacteria. It is notable for degrading toluene. Tol-4 is its type strain.
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.
Ferribacterium is a genus of bacteria from the family of Rhodocyclaceae which belongs to the class of Betaproteobacteria. Up to now there is only one species of this genus known.
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.
Ann Patricia Wood is a retired British biochemist and bacteriologist who specialized in the ecology, taxonomy and physiology of sulfur-oxidizing chemolithoautotrophic bacteria and how methylotrophic bacteria play a role in the degradation of odour causing compounds in the human mouth, vagina and skin. The bacterial genus Annwoodia was named to honor her contributions to microbial research in 2017.
