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.
The Methylococcaceae are a family of bacteria that obtain their carbon and energy from methane, called methanotrophs.
The Pseudomonadales are an order of Pseudomonadota. A few members are pathogens, such as species of Pseudomonas, Moraxella, and Acinetobacter, which may cause disease in humans, animals and plants.
The Aeromonadales are an order of Pseudomonadota, with 10 genera in two families. The species are anaerobic. The cells are rod-shaped. Some species of this order are motile by a single polar flagellum; others are not motile.
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.
The Xanthomonadales are a bacterial order within the Gammaproteobacteria. They are one of the largest groups of bacterial phytopathogens, harbouring species such as Xanthomonas citri, Xanthomonas euvesicatoria, Xanthomonas oryzae and Xylella fastidiosa. These bacteria affect agriculturally important plants including tomatoes, bananas, citrus plants, rice, and coffee. Many species within the order are also human pathogens. Species within the genus Stenotrophomonas are multidrug resistant opportunistic pathogens that are responsible for nosocomial infections in immunodeficient patients.
The Cardiobacteriaceae are a family of Pseudomonadota, given their own order. They are Gram-negative and rod-shaped, with diameters around 0.5 to 1.7 μm and lengths from 1–6 μm.
The Alteromonadales are an order of Pseudomonadota. Although they have been treated as a single family, the Alteromonadaceae, they were divided into eight by Ivanova et al. in 2004. The cells are straight or curved rods. They are motile by the use of a single flagellum. Most of the species are marine.
The Thiotrichaceae are a family of Pseudomonadota, including Thiomargarita namibiensis, the largest known bacterium. Some species are movable by gliding, Thiospira by using flagella.
The Alteromonadaceae are a family of Pseudomonadota. They are now one of several families in the order Alteromonadales, including Alteromonas and its closest relatives. Species of this family are mostly rod-like shaped and motile by using one polar flagellum.
The Aeromonadaceae are Gram-negative bacteria. The species are facultative anaerobic organisms. The cells are rod-shaped. They are mostly found in estuarine waters and fresh water, also in soil and sewage. Some are pathogenic for humans and other animals such as fishes and frogs.
A diplococcus is a round bacterium that typically occurs in the form of two joined cells.
Moraxella is a genus of gram-negative bacteria in the family Moraxellaceae. It is named after the Swiss ophthalmologist Victor Morax. The organisms are short rods, coccobacilli, or as in the case of Moraxella catarrhalis, diplococci in morphology, with asaccharolytic, oxidase-positive, and catalase-positive properties. M. catarrhalis is the clinically most important species under this genus.
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. It is composed by all Gram-negative microbes and is the most phylogenetically and physiologically diverse class of Proteobacteria.
Moraxella bovis is a Gram-negative, aerobic, oxidase-positive rod-shaped bacterium. It is the cause of infectious bovine keratoconjunctivitis, a contagious ocular disease of cattle, referred to colloquially as pinkeye or New Forest eye. M. bovis was first associated with pinkeye in cattle 1915 in Bengal, India
Moraxella osloensis is a Gram-negative oxidase-positive, aerobic bacterium within the family Moraxellaceae in the gamma subdivision of the purple bacteria.
Moraxella lacunata is a rod-shaped, Gram-negative, nonmotile bacterium, generally present as diploid pairs. It causes one of the commonest forms of catarrhal conjunctivitis.
Psychrobacter is a genus of Gram-negative, osmotolerant, oxidase-positive, psychrophilic or psychrotolerant, aerobic bacteria which belong to the family Moraxellaceae and the class Gammaproteobacteria. The shape is typically cocci or coccobacilli. Some of those bacteria were isolated from humans and can cause humans infections such as endocarditis and peritonitis. This genus of bacteria is able to grow at temperatures between −10 and 42 °C. Rudi Rossau found through DNA-rRNA hybridization analysis that Psychrobacter belongs to the Moraxellaceae. The first species was described by Juni and Heym. Psychrobacter occur in wide range of moist, cold saline habitats, but they also occur in warm and slightly saline habitats.
Moraxella boevrei is a Gram-negative, oxidase- and catalase-positive, aerobic nonmotile bacterium in the genus Moraxella, which was isolated from the nasal flora of healthy goats in Lyon in France.
Elizabeth Osborne King was an American microbiologist who discovered and described bacteria of medical importance at the United States Centers for Disease Control and Prevention from the late 1940s through the early 1960s. A 1984 CDC manual dedication referred to King as "internationally known as an authority on a variety of unusual bacteria." The genera Kingella and Elizabethkingia and several species of bacteria are named to honor her for her pioneering work. King died of cancer on April 8, 1966, in Atlanta, where she is interred in Oakland Cemetery.
