[4][5][6][7][8] 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.

The generic name Pseudomonas created for these organisms was defined in rather vague terms by Walter Migula in 1894 and 1900 as a genus of Gram-negative, rod-shaped, and polar-flagellated bacteria with some sporulating species.

[17][18] In 2020, a phylogenomic analysis of 494 complete Pseudomonas genomes identified two well-defined species (P. aeruginosa and P. chlororaphis) and four wider phylogenetic groups (P. fluorescens, P. stutzeri, P. syringae, P. putida) with a sufficient number of available proteomes.

[21] In 2021, a broad phylogenomic analysis on this genus led to the reorganization of the species included in Pseudomonas, leading to the creation of several new genera to accommodate some of them[22].

For example, several P. aeruginosa-specific core proteins were identified that are known to play an important role in this species' pathogenicity, such as CntL, CntM, PlcB, Acp1, MucE, SrfA, Tse1, Tsi2, Tse3, and EsrC.

[citation needed] Pseudomonas may be the most common nucleator of ice crystals in clouds, thereby being of utmost importance to the formation of snow and rain around the world.

These bacteria produce a vast array of secondary metabolites[30], including antibiotics, siderophores, and biosurfactants, which contribute to their ecological versatility and biotechnological potential.

are naturally resistant to penicillin and the majority of related beta-lactam antibiotics, but a number are sensitive to piperacillin, imipenem, ticarcillin, or ciprofloxacin.

[citation needed] This ability to thrive in harsh conditions is a result of their hardy cell walls that contain proteins known as porins.

[33] This low susceptibility is attributable to a concerted action of multidrug efflux pumps with chromosomally encoded antibiotic resistance genes (e.g., mexAB-oprM, mexXY, etc.

Some recent studies have shown phenotypic resistance associated to biofilm formation or to the emergence of small-colony-variants, which may be important in the response of P. aeruginosa populations to antibiotic treatment.

The bacterium possesses a wide range of secretion systems, which export numerous proteins relevant to the pathogenesis of clinical strains.

Notable species demonstrated as suitable for use as bioremediation agents include: Pseudomonas is a genus of bacteria known to be associated with several diseases affecting humans, plants, and animals.

[53] Pseudomonas aeruginosa is highly contagious and has displayed resistance to antibiotic treatments, making it difficult to manage effectively.

Some strains of Pseudomonas are known to target white blood cells in various mammal species, posing risks to humans, cattle, sheep, and dogs alike.

Notably, the Pseudomonas syringae family is linked to diseases affecting a wide range of agricultural plants, with different strains showing adaptations to specific host species.

[55] Similar types of fragments from differing organisms are visualized and their lengths compared to each other by Southern blotting or by the much faster method of polymerase chain reaction (PCR).

[56] Around 51% of Pseudomonas bacteria found in dairy processing plants are P. fluorescens, with 69% of these isolates possessing proteases, lipases, and lecithinases which contribute to degradation of milk components and subsequent spoilage.

[57] Electronic nose technology allows fast and continuous measurement of microbial food spoilage by sensing odours produced by these volatile compounds.

α proteobacteria: P. abikonensis, P. aminovorans, P. azotocolligans, P. carboxydohydrogena, P. carboxidovorans, P. compransoris, P. diminuta, P. echinoides, P. extorquens, P. lindneri, P. mesophilica, P. paucimobilis, P. radiora, P. rhodos, P. riboflavina, P. rosea, P. vesicularis.

β proteobacteria: P. acidovorans, P. alliicola, P. antimicrobica, P. avenae, P. butanovora, P. caryophylli, P. cattleyae, P. cepacia, P. cocovenenans, P. delafieldii, P. facilis, P. flava, P. gladioli, P. glathei, P. glumae, P. huttiensis, P. indigofera, P. lanceolata, P. lemoignei, B. mallei, P. mephitica, P. mixta, P. palleronii, P. phenazinium, P. pickettii, P. plantarii, P. pseudoflava, B. pseudomallei, P. pyrrocinia, P. rubrilineans, P. rubrisubalbicans, P. saccharophila, P. solanacearum, P. spinosa, P. syzygii, P. taeniospiralis, P. terrigena, P. testosteroni.

γ proteobacteria: P. beijerinckii, P. diminuta, P. doudoroffii, P. elongata, P. flectens, P. marinus, P. halophila, P. iners, P. marina, P. nautica, P. nigrifaciens, P. pavonacea,[67] P. piscicida, P. stanieri.