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.
In biological classification, class is a taxonomic rank, as well as a taxonomic unit, a taxon, in that rank. Other well-known ranks in descending order of size are life, domain, kingdom, phylum, order, family, genus, and species, with class fitting between phylum and order. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the prefix sub-: subclass. For example, dogs are in the class Mammalia.
Bacteria are a type of biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a number of shapes, ranging from spheres to rods and spirals. Bacteria were among the first life forms to appear on Earth, and are present in most of its habitats. Bacteria inhabit soil, water, acidic hot springs, radioactive waste, and the deep portions of Earth's crust. Bacteria also live in symbiotic and parasitic relationships with plants and animals. Most bacteria have not been characterised, and only about half of the bacterial phyla have species that can be grown in the laboratory. The study of bacteria is known as bacteriology, a branch of microbiology.
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 Gammaproteobacteria comprise several medically and scientifically important groups of bacteria, such as the Enterobacteriaceae, Vibrionaceae, and Pseudomonadaceae. A number of important pathogens belong to this class, e.g. Salmonella spp. (enteritis and typhoid fever), Yersinia pestis (plague), Vibrio cholerae (cholera), Pseudomonas aeruginosa (lung infections in hospitalized or cystic fibrosis patients), and Escherichia coli (food poisoning). Important plant pathogens such as Xanthomonas axonopodis pv. citri (citrus canker), Pseudomonas syringae pv. actinidiae (kiwifruit Psa outbreak), and Xylella fastidiosa are also Gammaproteobacteria. Members of Chromatium are photosynthetic and oxidize hydrogen sulfide instead of water, producing sulfur as a waste product. Some Gammaproteobacteria are methane oxidizers, and many are symbiotic with geothermic ocean vent-dwelling animals.
The Enterobacteriaceae are a large family of Gram-negative bacteria. This family is the only representative in the order Enterobacteriales of the class Gammaproteobacteria in the phylum Proteobacteria.
The Vibrionaceae are a family of Proteobacteria given their own order. Inhabitants of fresh or salt water, several species are pathogenic, including the type species Vibrio cholerae, which is the agent responsible for cholera. Most bioluminescent bacteria belong to this family, and are typically found as symbionts of deep-sea animals.
The Pseudomonadaceae are family of bacteria which includes the genera Azomonas, Azomonotrichon, Azorhizophilus, Azotobacter, Cellvibrio, Mesophilobacter, Pseudomonas, Rhizobacter, Rugamonas, and Serpens. The family Azotobacteriaceae was recently reclassified into this family.
|Phylogeny of Gammaproteobacteria|
|Phylogeny of Gammaproteobacteria after Not all orders are monophyletic, consequently families or genera are shown for Pseudomonadales, Oceanospirillales, and Alteromonadales. In the case of singleton orders, the genus is shown. (In bacterial taxonomy, orders have the suffix -ales, while families have -aceae.)|
A number of bacteria have been described as members of Gammaproteobacteria, but have not yet been assigned an order or family. These include bacteria of the genera Alkalimarinus , Alkalimonas , Arenicella , Gallaecimonas , Ignatzschineria , Litorivivens , Marinicella , Methylohalomonas , Methylonatrum , Plasticicumulans , Pseudohongiella , Sedimenticola , Thiohalobacter , Thiohalomonas , Thiohalorhabdus , Thiolapillus , and Wohlfahrtiimonas .
Alkalimarinus is a Gram-negative genus of bacteria from the class of Alteromonadaceae with one known species. Alkalimarinus sediminis has been isolated from sediments from the coast of Weihai in China.
Alkalimonas is a genus in the phylum Proteobacteria (Bacteria).
Arenicella is a genus of bacteria from the class of Alteromonadaceae.
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.
Pseudomonas is a genus of Gram-negative, Gammaproteobacteria, belonging to the family Pseudomonadaceae and containing 191 validly described species. The members of the genus demonstrate a great deal of metabolic diversity and consequently are able to colonize a wide range of niches. Their ease of culture in vitro and availability of an increasing number of Pseudomonas strain genome sequences has made the genus an excellent focus for scientific research; the best studied species include P. aeruginosa in its role as an opportunistic human pathogen, the plant pathogen P. syringae, the soil bacterium P. putida, and the plant growth-promoting P. fluorescens.
Burkholderia is a genus of Proteobacteria whose pathogenic members include the Burkholderia cepacia complex which attacks humans and Burkholderia mallei, responsible for glanders, a disease that occurs mostly in horses and related animals; Burkholderia pseudomallei, causative agent of melioidosis; and Burkholderia cepacia, an important pathogen of pulmonary infections in people with cystic fibrosis (CF).
The Methylococcaceae are a family of bacteria that obtain their carbon and energy from methane, called methanotrophs.
Methanotrophs are prokaryotes that metabolize methane as their only source of carbon and energy. They can be either bacteria or archaea and can grow aerobically or anaerobically, and require single-carbon compounds to survive.
The Pseudomonadales are an order of Proteobacteria. A few members are opportunistic pathogens, such as species of Pseudomonas, Moraxella, and Acinetobacter, which may cause pneumonia.
The Pasteurellaceae comprise a large family of Gram-negative bacteria. Most members live as commensals on mucosal surfaces of birds and mammals, especially in the upper respiratory tract. Pasteurellaceae are typically rod-shaped, and are a notable group of facultative anaerobes. Their biochemical characteristics can be distinguished from the related Enterobacteriaceae by the presence of oxidase, and from most other similar bacteria by the absence of flagella.
Acidithiobacillus is a genus of the Acidithiobacillia in the "Proteobacteria". Like all "Proteobacteria", Acidithiobacillus spp. are Gram-negative. Some members of this genus were classified as Thiobacillus spp., before they were reclassified in 2000.
The Chromatiaceae are the main family of purple sulfur bacteria. Many members conduct an anoxygenic photosynthesis. They are distinguished from the Ectothiorhodospiraceae by producing sulfur globules and storing them inside their cells. Most species of Ectothiorhodospiraceae are also purple sulfur bacteria but they store the globules outside their cells. The sulfur is an intermediate in the oxidization of sulfide, which is ultimately converted into sulfate, and may serve as a reserve.
Betaproteobacteria are a class of gram-negative bacteria, and one of the eight classes of the phylum Proteobacteria.
Alphaproteobacteria is a class of bacteria in the phylum Proteobacteria. Its members are highly diverse and possess few commonalities, but nevertheless share a common ancestor. Like all Proteobacteria, its members are gram-negative and some of its intracellular parasitic members lack peptidoglycan and are consequently gram variable.
Pseudomonas syringae is a rod-shaped, Gram-negative bacterium with polar flagella. As a plant pathogen, it can infect a wide range of species, and exists as over 50 different pathovars, all of which are available to researchers from international culture collections such as the NCPPB, ICMP, and others. Whether these pathovars represent a single species is unclear.
Pseudomonas savastanoi is a Gram-negative plant pathogenic bacterium that infects a variety of plants. It was once considered a pathovar of Pseudomonas syringae, but following DNA-relatedness studies, it was instated as a new species. It is named after Savastano, a worker who proved between 1887 and 1898 that olive knot are caused by bacteria.
Xanthomonas is a genus of Proteobacteria, many of which cause plant diseases.
Halo blight of bean is a bacterial disease caused by Pseudomonas syringae pv. phaseolicola. Halo blight’s pathogen is a gram-negative, aerobic, polar-flagellated and non-spore forming bacteria. This bacterial disease was first discovered in the early 1920s, and rapidly became the major disease of beans throughout the world. The disease favors the places where temperatures are moderate and plentiful inoculum is available.
The bacterial phyla are the major lineages, known as phyla or divisions, of the domain Bacteria.
Bacterial taxonomy is the taxonomy, i.e. the rank-based classification, of bacteria.
Conserved signature inserts and deletions (CSIs) in protein sequences provide an important category of molecular markers for understanding phylogenetic relationships. CSIs, brought about by rare genetic changes, provide useful phylogenetic markers that are generally of defined size and they are flanked on both sides by conserved regions to ensure their reliability. While indels can be arbitrary inserts or deletions, CSIs are defined as only those protein indels that are present within conserved regions of the protein.
Medical Subject Headings (MeSH) is a comprehensive controlled vocabulary for the purpose of indexing journal articles and books in the life sciences; it serves as a thesaurus that facilitates searching. Created and updated by the United States National Library of Medicine (NLM), it is used by the MEDLINE/PubMed article database and by NLM's catalog of book holdings. MeSH is also used by ClinicalTrials.gov registry to classify which diseases are studied by trials registered in ClinicalTrials.