PSEUDOMONAS FLUORESCENS

'''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.

Contents

General characteristics

The name

Genome sequencing projects

Biocontrol properties

Medical Properties

References

External links

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.
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' is due to the fact that secretes 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:

★ that the bacteria might induce systemic resistance in the host plant, so it can better resist attack by a true pathogen

★ the bacteria might out compete 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
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^[11].

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^[12].
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^[13].
It is also used in milk to make yogurt.
United States Patents: 6489358, 4873012, 6156792

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. Phylogenetic affiliation of the pseudomonads based on 16S rRNA sequence, Anzai, ''et al.'', , , Int J Syst Evol Microbiol, 2000, Jul
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.
6. C D Cox and P Adams (1985) Infection and Immunity 48(1): 130–138
7. http://www.sanger.ac.uk/Projects/P_fluorescens/
8. http://cmr.tigr.org/tigr-scripts/CMR/GenomePage.cgi?org=gpf
9. http://cmr.tigr.org/tigr-scripts/CMR/GenomePage.cgi?org=ntpf02
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. Haas D, Defago G. (2005) Biological control of soil-borne pathogens by fluorescent pseudomonads.
Nature Reviews in Microbiology 3(4):307-19 PMID 15759041
12. http://www.netdoctor.co.uk/medicines/100000220.html
13. 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

External links

★ www.pseudomonas.com, the Pseudomonas genome database

★ Migula's Systematic Bacteriology (in German)