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Pseudomonas
From Wikipedia, the free encyclopedia
Pseudomonas is a genus of gamma proteobacteria. The name Pseudomonas loosely means 'false unit', being derived from the Greek words pseudo ('false') and monas ('a single unit').
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Members of the genus display the following defining characteristics:[1]
- Rod shaped
- Gram negative
- One or more polar flagella, providing motility
- Aerobic
- Non spore forming
- Tests positive for catalase test
Pseudomonas aeruginosa is the type species for the genus.
Other characteristics which tend to be associated with Pseudomonas species (although there are some exceptions) include secretion of pyoverdin (also known as fluorescein), a fluorescent yellow-green siderophore[2] under iron-limiting conditions; certain Pseudomonas species may also produce additional types of siderophore, such as pyocyanin by Pseudomonas aeruginosa[3] and thioquinolobactin by Pseudomonas fluorescens[4], for example. Pseudomonas species also typically give a positive result to the oxidase test, the absence of gas formation from glucose, glucose is oxidised in oxidation/fermentation test using Hugh and Leifson O/F test, hemolytic (on blood agar), indole negative, methyl red negative, Voges Proskauer test negative.
The genus demonstrates a great deal of metabolic diversity, and consequently are able to colonise a wide range of niches. [5] 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 Pseudomonas aeruginosa in its role as an opportunistic human pathogen, the plant pathogen Pseudomonas syringae, the soil bacterium Pseudomonas putida, and the plant growth promoting Pseudomonas fluorescens.
All species and strains of Pseudomonas are Gram-negative rods, and have historically been classified as strict aerobes. Exceptions to this classification have recently been discovered in Pseudomonas biofilms.[6] A significant number can produce exopolysaccharides that are known as slime layers. Secretion of exopolysaccharide makes it difficult for Pseudomonads to be phagocytosed by mammalian white blood cells.[7] Slime production also contributes to surface-colonising biofilms which are difficult to remove from food preparation surfaces. Growth of Pseudomonads on spoiling foods can generate a "fruity" odor.
Pseudomonas have the ability to metabolise a variety of diverse nutrients. Combined with the ability to form biofilms, they are thus able to survive in a variety of unexpected places. For example, they have been found in areas where pharmaceuticals are prepared. A simple carbon source, such as soap residue or cap liner-adhesives is a suitable place for the Pseudomonads to thrive. Other unlikely places where they have been found include antiseptics such as quaternary ammonium compounds and bottled mineral water.
Being gram-negative bacteria, most Pseudomonas spp. are naturally resistant to penicillin and the majority of related beta-lactam antibiotics, but a number are sensitive to piperacillin, imipenem, tobramycin, or ciprofloxacin.[7]
This ability to thrive in harsh conditions is a result of their hardy cell wall that contains porins. Their resistance to most antibiotics is attributed to efflux pumps called ABC transporters, which pump out some antibiotics before they are able to act.
P. aeruginosa is an opportunistic human pathogen, most commonly affecting patients already suffering from cystic fibrosis[8] or AIDS[9] who are immunocompromised as a result. Infection can affect many different parts of the body, but infections typically target the respiratory tract, causing bacterial pneumonia. Treatment of such infections can be difficult due to multiple antibiotic resistance[10].
P. oryzihabitans can also be a human pathogen, although infections are rare. It can cause peritonitis[11], endophthalmitis[12], septicemia and bacteremia.
P. plecoglossicida is a fish pathogenic species, causing hemorrhagic ascites in the ayu (Plecoglossus altivelis)[13].
P. syringae is a prolific plant pathogen. It exists as over 50 different pathovars, many of which demonstrate a high degree of host plant specificity. There are numerous other Pseudomonas species that can act as plant pathogens, notably all of the other members of the P. syringae subgroup, but P. syringae is the most widespread and best studied.
Although not strictly a plant pathogen, P. tolaasii can be a major agricultural problem, as it can cause bacterial blotch of cultivated mushrooms[14].
Since the mid 1980s, certain members of the Pseudomonas genus have been applied to cereal seeds or applied directly to soils as a way of preventing the growth or establishment of crop pathogens. This practice is generically referred to as biocontrol.
Recently, 16S rRNA sequence analysis redefined the taxonomy of many bacterial species previously classified as being in the Pseudomonas genus[15]. Species which moved from the Pseudomonas genus are listed below; clicking on a species will show its new classification. Note that the term 'Pseudomonad' does not apply strictly to just the Pseudomonas genus, and can be used to also include previous members such as the genera Burkholderia and Ralstonia.
α proteobacteria
- P. abikonensis
- P. aminovorans
- P. carboxydohydrogena
- P. carboxidovorans
- P. compransoris
- P. diminuta
- P. echinoides
- P. extorquens
- P. mesophilica
- P. paucimobilis
- P. radiora
- P. rhodos
- P. riboflavina
- P. rosea
- P. vesicularis
- P. lindneri
β proteobacteria
- P. acidovorans
- P. alliicola
- P. andropogonis
- P. antimicrobica
- P. avenae
- P. butanovorae
- P. caryophylli
- P. cattleyae
- P. cepacia
- P. cocovenenans
- P. delafieldii
- P. facilis
- P. flava
- P. gladioli
- P. glathei
- P. glumae
- P. graminis
- P. huttiensis
- P. indigofera
- P. lanceolata
- P. lemoignei
- P. mallei
- P. mephitica
- P. mixta
- P. palleronii
- P. phenazinium
- P. pickettii
- P. plantarii
- P. phenazinium
- P. pseudoflava
- P. pseudomallei
- P. pyrrocinia
- P. rubrilineans
- P. rubrisubalbicans
- P. saccharophila
- P. solanacearum
- P. spinosa
- P. syzygii
- P. taeniospiralis
- P. terrigena
- P. testosteroni
- P. woodsii
γ-β proteobacteria
- P. beteli
- P. boreopolis
- P. cissicola
- P. geniculata
- P. hibiscicola
- P. maltophilia
- P. ochracea
- P. pictorum
γ proteobacteria
- P. beijerinckii
- P. diminuta
- P. doudoroffii
- P. elongata
- P. flectens
- P. graveolens
- P. halodurans
- P. halophila
- P. iners
- P. lemonnieri
- P. marina
- P. mildenbergii
- P. multiresinivorans
- P. nautica
- P. nigrifaciens
- P. ovalis
- P. pavonacea
- P. piscicida
- P. schuylkilliensis
- P. stanieri
- P. vendrelli
δ proteobacteria
- P. formicans
- ^ Krieg, N.R. (Ed.) (1984) Bergey's Manual of Systematic Bacteriology, Volume 1. Williams & Wilkins. ISBN 0683041088
- ^ Meyer JM, Geoffroy VA, Baida N, Gardan L, Izard D, Lemanceau P, Achouak W, Palleroni NJ. (2002) Siderophore typing, a powerful tool for the identification of fluorescent and nonfluorescent pseudomonads. Applied Environmental Microbiology. 68(6):2745-53. PMID 12039729
- ^ Lau GW, Hassett DJ, Ran H, Kong F. (2004) The role of pyocyanin in Pseudomonas aeruginosa infection. Trends in Molecular Medicine 10(12):599-606. PMID 15567330
- ^ Matthijs S, Tehrani KA, Laus G, Jackson RW, Cooper RM, Cornelis P. (2007) Thioquinolobactin, a Pseudomonas siderophore with antifungal and anti-Pythium activity. Environmental Microbiology 9(2):425-34. PMID 17222140
- ^ Madigan M; Martinko J (editors). (2005). Brock Biology of Microorganisms, 11th ed., Prentice Hall. ISBN 0131443291.
- ^ Hassett D, Cuppoletti J, Trapnell B, Lymar S, Rowe J, Yoon S, Hilliard G, Parvatiyar K, Kamani M, Wozniak D, Hwang S, McDermott T, Ochsner U (2002). "Anaerobic metabolism and quorum sensing by Pseudomonas aeruginosa biofilms in chronically infected cystic fibrosis airways: rethinking antibiotic treatment strategies and drug targets". Adv Drug Deliv Rev 54 (11): 1425-43. PMID 12458153.
- ^ a b Ryan KJ; Ray CG (editors) (2004). Sherris Medical Microbiology, 4th ed., McGraw Hill. ISBN 0838585299.
- ^ Elkin S, Geddes D. (2003) Pseudomonal infection in cystic fibrosis: the battle continues. Expert Review of Anti Infective Therapy 1(4):609-18. PMID 15482158
- ^ Shanson DC. (1990) Septicaemia in patients with AIDS. Transactions of the Royal Society of Tropical Medicine and Hygiene 84 Suppl 1:14-6. PMID 2201108
- ^ McGowan JE Jr. (2006) Resistance in nonfermenting gram-negative bacteria: multidrug resistance to the maximum. The American Journal of Medicine 119(6 Suppl 1):S29-36; discussion S62-70. PMID 16735148
- ^ Levitski-Heikkila TV, Ullian ME. (2005) Peritonitis with multiple rare environmental bacteria in a patient receiving long-term peritoneal dialysis. American Journal of Kidney Disease 46(6):e119-24. PMID 16310563
- ^ Yu EN, Foster CS. (2002) Chronic postoperative endophthalmitis due to Pseudomonas oryzihabitans. American Journal of Ophthalmology 134(4):613-4. PMID 12383826
- ^ Nishimori, et al. "Pseudomonas plecoglossicida sp. nov., the causative agent of bacterial haemorrhagic ascites of ayu, Plecoglossus altivelis." Int J Syst Evol Microbiol. 2000 Jan; 50 Pt 1:83-9. PMID 10826790
- ^ Brodey, C.L., Rainey, P.B., Tester, M. and Johnstone, K. ( 1991) Bacterial blotch disease of the cultivated mushroom is caused by an ion channel forming lipodepsipeptide toxin. Molecular Plant–Microbe Interaction 1, 407– 411.
- ^ Anzai Y, Kim H, Park, JY, Wakabayashi H (2000). "Phylogenetic affiliation of the pseudomonads based on 16S rRNA sequence". Int J Syst Evol Microbiol 50: 1563-89. PMID 10939664.