Pseudomonas fluorescens

Pseudomonas fluorescens
Pseudomonas fluorescens under white light.
The same plate under UV light.
Scientific classification
Kingdom:	Bacteria
Phylum:	Proteobacteria
Class:	Gamma Proteobacteria
Order:	Pseudomonadales
Family:	Pseudomonadaceae
Genus:	Pseudomonas
Species:	P. fluorescens
Binomial name
Pseudomonas fluorescens (Flügge 1886) Migula, 1895
Type strain
ATCC 13525 CCUG 1253 CCEB 546 CFBP 2102 CIP 69.13 DSM 50090 JCM 5963 LMG 1794 NBRC 14160 NCCB 76040 NCIMB 9046 NCTC 10038 NRRL B-14678 VKM B-894
Synonyms
Bacillus fluorescens liquefaciens Flügge 1886 Bacillus fluorescens Trevisan 1889 Bacterium fluorescens (Trevisan 1889) Lehmann and Neumann 1896 Liquidomonas fluorescens (Trevisan 1889) Orla-Jensen 1909 Pseudomonas lemonnieri (Lasseur) Breed 1948 Pseudomonas schuylkilliensis Chester 1952 Pseudomonas washingtoniae (Pine) Elliott

Pseudomonas fluorescens is a common Gram-negative, rod-shaped bacterium.^[1] It belongs to the Pseudomonas genus; 16S rRNA analysis has placed P. fluorescens in the P. fluorescens group within the genus,^[2] to which it lends its name.

General characteristics

P. fluorescens has multiple flagella. It has an extremely versatile metabolism, and can be found in the soil and in water. It is an obligate aerobe, but certain strains are capable of using nitrate instead of oxygen as a final electron acceptor during cellular respiration.

Optimal temperatures for growth of Pseudomonas fluorescens are 25-30 degrees Celsius. It tests positive for the oxidase test. Pseudomonas fluorescens is also a nonsaccharolytic bacteria.

Heat-stable lipases and proteases are produced by Pseudomonas fluorescens and other similar pseudomonads.^[3] These enzymes cause milk to spoil, by causing bitterness, casein breakdown, and ropiness due to production of slime and coagulation of proteins.^[4][5]

The name

The word Pseudomonas means 'false unit', being derived from the Greek words pseudo (Greek: ψευδο 'false') and monas (Latin: monas, fr. Greek: μονάς/μονάδα 'a single unit'). The word was used early in the history of microbiology to refer to germs. The name 'fluorescens' refers to the microbe's secretion of a soluble fluorescent pigment called pyoverdin (formerly called fluorescein), which is a type of siderophore.^[6]

Genome sequencing projects

The genomes of P. fluorescens strains SBW25,^[7] Pf-5^[8] and PfO-1^[9] have been sequenced.

Biocontrol properties

Some P. fluorescens strains (CHA0 or Pf-5, for example) present biocontrol properties, protecting the roots of some plant species against parasitic fungi such as Fusarium or Pythium, as well as some phytophagous nematodes.^[10]

It is not clear exactly how the plant growth-promoting properties of P. fluorescens are achieved; theories include:

• the bacteria might induce systemic resistance in the host plant, so it can better resist attack by a true pathogen
• the bacteria might outcompete other (pathogenic) soil microbes, e.g., by siderophores, giving a competitive advantage at scavenging for iron
• the bacteria might produce compounds antagonistic to other soil microbes, such as phenazine-type antibiotics or hydrogen cyanide

To be specific, certain P. fluorescens isolates produce the secondary metabolite 2,4-diacetylphloroglucinol (2,4-DAPG), the compound found to be responsible for antiphytopathegenic and biocontrol properties in these strains.^[11] The phl gene cluster encodes factors for 2,4-DAPG biosynthesis, regulation, export, and degradation. Eight genes, phlHGFACBDE, are annotated in this cluster and conserved organizationally in 2,4-DAPG-producing strains of P. fluorescens. Of these genes, phlD encodes a type III polyketide synthase, representing the key biosynthetic factor for 2,4-DAPG production. PhlD shows similarity to plant chalcone synthases and has been theorized to originate from horizontal gene transfer.^[12] But phylogenetic and genomic analysis has revealed that the entire phl gene cluster is ancestral to P. fluorescens, many strains have lost the capacity, and it exists on different genomic regions among strains.^[13]

There is experimental evidence to support all of these theories, in certain conditions; a good review of the topic is written by Haas and Defago.^[14]

The strain referred to as Pf-CL145A has proved itself a promising solution to the invasive Dreissena( zebra and quagga) mussels. The strain of the bacteria produces toxins that destroy the digestive system of the mussels and produces a >90% kill rate.

Several strains of "P. Fluorescens", such as Pf-5 and JL3985, have developed a natural resistance to ampicillin and streptomycin^[15]. These antibiotics are regularly used in biological research as a selective pressure tool to promote plasmid expression.

Medical Properties

By culturing Pseudomonas fluorescens, Mupirocin (an antibiotic) can be produced, which has been found to be useful in treating skin, ear, and eye disorders.^[16] Mupirocin free acid and its salts and esters are agents currently used in creams, ointments, and sprays as a treatment of Methicillin-resistant Staphylococcus aureus (MRSA) infection.

P. fluorescens demonstrates hemolytic activity and, as a result, has been known to infect blood transfusions.^[17]

It is also used in milk to make yogurt.

United States Patents: 6489358, 4873012, 6156792

Disease

P. fluorescens is an unusual cause of disease in humans, and usually affects patients with compromised immune systems (e.g., patients on cancer treatment). From 2004 to 2006, there was an outbreak of P. fluorescens in the United States, involving 80 patients in six states. The source of the infection was contaminated heparinized saline flushes being used with cancer patients.^[18]

References

1. ^ Palleroni, N.J. (1984) Pseudomonadaceae. Bergey's Manual of Systematic Bacteriology. Krieg, N. R. and Holt J. G. (editors) Baltimore: The Williams and Wilkins Co., pg. 141 - 199
2. ^ Anzai, et al.; Kim, H; Park, JY; Wakabayashi, H; Oyaizu, H (2000, Jul). "Phylogenetic affiliation of the pseudomonads based on 16S rRNA sequence". Int J Syst Evol Microbiol 50 (Pt 4): 1563–89. doi:10.1099/00207713-50-4-1563. PMID 10939664. 
3. ^ Frank, J.F. 1997. Milk and dairy products. In Food Microbiology, Fundamentals and Frontiers, ed. M.P. Doyle, L.R. Beuchat, T.J. Montville, ASM Press, Washington, p. 101.
4. ^ Jay, J.M. 2000. Taxonomy, role, and significance of microorganisms in food. In Modern Food Microbiology, Aspen Publishers, Gaithersburg MD, p. 13.
5. ^ Ray, B. 1996. Spoilage of Specific food groups. In Fundamental Food Microbiology, CRC Press, Boca Raton FL, p. 220. I
6. ^ C D Cox and P Adams (1985) Infection and Immunity 48(1): 130–138
7. ^ Pseudomonas fluorescens
8. ^ Pseudomonas fluorescens Pf-5 Genome Page
9. ^ Pseudomonas fluorescens PfO-1 Genome Page
10. ^ Haas, D. and Keel, C. (2003) Regulation of antibiotic production in root-colonizing Pseudomonas spp. and relevance for biological control of plant disease. Annual Reviews of Phytopathology 41, 117-153 PMID 12730389
11. ^ Bangera, M. G., and L. S. Thomashow. 1999. Identification and characterization of a gene cluster for synthesis of the polyketide antibiotic 2,4-diacetylphloroglucinol from pseudomonas fluorescens q2-87. Journal of Bacteriology 181:3155-3163.
12. ^ Bangera, M. G., and L. S. Thomashow. 1999. Identification and characterization of a gene cluster for synthesis of the polyketide antibiotic 2,4-diacetylphloroglucinol from pseudomonas fluorescens q2-87. Journal of Bacteriology 181:3155-3163.
13. ^ Moynihan, J. A., J. P. Morrissey, E. R. Coppoolse, W. J. Stiekema, F. O'Gara, and E. F. Boyd. 2009. Evolutionary history of the phl gene cluster in the plant-associated bacterium pseudomonas fluorescens. Applied and Environmental Microbiology 75:2122-2131.
14. ^ Haas D, Defago G. (2005) Biological control of soil-borne pathogens by fluorescent pseudomonads. Nature Reviews in Microbiology 3(4):307-19 doi:10.1038/nrmicro1129 PMID 15759041
15. ^ Alain Sarniguet et al. (1995). "The sigma factor σ^s affects antibiotic production and biological control activity of Pseudomonas fluorescens Pf-5". P Natl Aca Sci USA 92: 12255–12259. 
16. ^ Bactroban
17. ^ Gibb AP, Martin KM, Davidson GA, Walker B, Murphy WG. (1995) Rate of growth of Pseudomonas fluorescens in donated blood. Journal of Clinical Patholology 48(8):717-8. PMID 7560196
18. ^ Gershman MD, Kennedy DJ, Noble-Wang J, et al. (2008). "Multistate outbreak of Pseudomonas fluorescens bloodstream infection after exposure to contaminated heparinized saline flush prepared by a compounding pharmacy". Clin Infect Dis 47 (11): 1372–1379. doi:10.1086/592968. PMID 18937575. 

External links

• www.pseudomonasfluorescens.org
• www.pseudomonas.com, the Pseudomonas genome database
• Migula's Systematic Bacteriology (in German)
• UV fluorescent Pseudomonas video
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