Pseudomonas is a genus of Gram-negative, Gammaproteobacteria, belonging to the family Pseudomonadaceae and containing 191 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, P. lini, P. migulae, and P. graminis.
Pseudomonas fluorescens is a common Gram-negative, rod-shaped bacterium. It belongs to the Pseudomonas genus; 16S rRNA analysis as well as phylogenomic analysis has placed P. fluorescens in the P. fluorescens group within the genus, to which it lends its name.
Pseudomonas putida is a Gram-negative, rod-shaped, saprotrophic soil bacterium.
Pseudomonas aeruginosa is a common encapsulated, gram-negative, aerobic–facultatively anaerobic, rod-shaped bacterium that can cause disease in plants and animals, including humans. A species of considerable medical importance, P. aeruginosa is a multidrug resistant pathogen recognized for its ubiquity, its intrinsically advanced antibiotic resistance mechanisms, and its association with serious illnesses – hospital-acquired infections such as ventilator-associated pneumonia and various sepsis syndromes.
Pseudomonas alcaligenes is a Gram-negative aerobic bacterium used for bioremediation purposes of oil pollution, pesticide substances, and certain chemical substances, as it can degrade polycyclic aromatic hydrocarbons. It can be a human pathogen, but occurrences are very rare. Based on 16S rRNA analysis, P. alcaligenes has been placed in the P. aeruginosa group.
Pseudomonas chlororaphis is a bacterium used as a soil inoculant in agriculture and horticulture. It can act as a biocontrol agent against certain fungal plant pathogens via production of phenazine-type antibiotics. Based on 16S rRNA analysis, similar species have been placed in its group.
Pseudomonas fragi is a psychrophilic, Gram-negative bacterium that is responsible for dairy spoilage. Unlike many other members of the genus Pseudomonas, P. fragi does not produce siderophores. Optimal temperature for growth is 30 °C, however it can grow between 0 and 35 °C. Based on 16S rRNA analysis, P. fragi has been placed in the P. chlororaphis group.
Pseudomonas avellanae is a Gram-negative plant pathogenic bacterium. It is the causal agent of bacterial canker of hazelnut. Based on 16S rRNA analysis, P. avellanae has been placed in the P. syringae group. This species was once included as a pathovar of Pseudomonas syringae, but following DNA-DNA hybridization, it was instated as a separate species. Following ribotypical analysis Pseudomonas syringae pv. theae was incorporated into this species.
Pseudomonas corrugata is a Gram-negative, plant-pathogenic bacterium that causes pith necrosis in tomatoes. Based on 16S rRNA analysis, P. corrugata has been placed in the P. fluorescens group. For a more comprehensive phylogenetic analysis of P. corrugata and its closely related phytopathogenic bacterium P. mediterranea, refer to Trantas et al. 2015.
Pseudomonas marginalis is a soil bacterium that can cause soft rots of plant tissues. It infects poinsettia, lettuce, and crucifers.
Pseudomonas tolaasii is a species of Gram-negative soil bacteria that is the causal agent of bacterial blotch on cultivated mushrooms. It is known to produce a toxin, called tolaasin, which is responsible for the brown blotches associated with the disease. It also demonstrates hemolytic activity, causing lysis of erythrocytes. Based on 16S rRNA analysis, P. tolaasii has been placed in the P. fluorescens group.
Pseudomonas denitrificans is a Gram-negative aerobic bacterium that performs denitrification. It was first isolated from garden soil in Vienna, Austria. It overproduces cobalamin (vitamin B12), which it uses for methionine synthesis and it has been used for manufacture of the vitamin. Scientists at Rhône-Poulenc Rorer took a genetically engineered strain of the bacteria, in which eight of the cob genes involved in the biosynthesis of the vitamin had been overexpressed, to establish the complete sequence of methylation and other steps in the cobalamin pathway.
Pseudomonas mendocina is a Gram-negative environmental bacterium that can cause opportunistic infections, such as infective endocarditis and spondylodiscitis, although cases are very rare. It has potential use in bioremediation as it is able to degrade toluene. Based on 16S rRNA analysis, P. mendocina has been placed in the P. aeruginosa group.
Pseudomonas anguilliseptica is a Gram-negative bacterium that is pathogenic to fish. It was first isolated from Japanese eels. Based on 16S rRNA analysis, P. anguilliseptica has been placed in the P. aeruginosa group.
Pseudomonas veronii is a Gram-negative, rod-shaped, fluorescent, motile bacterium isolated from natural springs in France. It may be used for bioremediation of contaminated soils, as it has been shown to degrade a variety of simple aromatic organic compounds. Based on 16S rRNA analysis, P. veronii has been placed in the P. fluorescens group.
Pseudomonas amygdali is a Gram-negative plant pathogenic bacterium. It is named after its ability to cause disease on almond trees. Different analyses, including 16S rRNA analysis, DNA-DNA hybridization, and MLST clearly placed P. amygdali in the P. syringae group together with the species Pseudomonas ficuserectae and Pseudomonas meliae, and 27 pathovars of Pseudomonas syringae/Pseudomonas savastanoi, constituting a single, well-defined phylogenetic group which should be considered as a single species. This phylogenetic group has not been formally named because of the lack of reliable means to differentiate it phenotypically from closely related species, and it is currently known as either genomospecies 2 or phylogroup 3. When it is formally named, the correct name for this new species should be Pseudomonas amygdali, which takes precedence over all the other names of taxa from this group, including Pseudomonas savastanoi, which is and inadequate and confusing name whose use is not recommended.
Pseudomonas aurantiaca is an orange Gram-negative soil bacterium, originally isolated from the rhizosphere soil of potatoes. It produces di-2,4-diacetylfluoroglucylmethan, which is antibiotically active against Gram-positive organisms. It has shown potential for use as a biocontrol agent against plant-pathogenic microbes. Based on 16S rRNA analysis, P. aurantiaca has been placed in the P. chlororaphis group.
Pseudomonas migulae is a fluorescent, Gram-negative, rod-shaped bacterium isolated from natural mineral waters in France. This bacterium has also been isolated from endophytic tissues of lodgepole pine trees growing on gravel mining sites with potential to perform biological nitrogen fixation and plant growth promotion. Based on 16S rRNA analysis, P. migulae has been placed in the P. fluorescens group.
Pseudomonas stutzeri is a Gram-negative soil bacterium that is motile, has a single polar flagellum, and is classified as bacillus, or rod-shaped. While this bacterium was first isolated from human spinal fluid, it has since been found in many different environments due to its various characteristics and metabolic capabilities. P. stutzeri is an opportunistic pathogen in clinical settings, although infections are rare. Based on 16S rRNA analysis, this bacterium has been placed in the P. stutzeri group, to which it lends its name.
Pseudomonas nitroreducens is an aerobic, Gram-negative soil bacterium first isolated from oil brine in Japan. It is able to synthesise polyhydroxybutyrate homopolymer from medium chain length fatty acids. Based on 16S rRNA analysis, P. nitroreducens has been placed in the P. aeruginosa group.
