Document Detail

Phase variation in Flavobacterium psychrophilum: characterization of two distinct colony phenotypes.
MedLine Citation:
PMID:  20597429     Owner:  NLM     Status:  MEDLINE    
Four 'smooth' and 4 'rough' colony phenotypes of the Gram-negative fish pathogen Flavobacterium psychrophilum isolated from rainbow trout Oncorhynchus mykiss were characterized using biochemical, physiological, molecular and virulence tests to better understand the pathogenesis of the bacterium. Biochemically, the 2 cell types did not react significantly differently. Physiologically, the 2 phenotypes had distinct characteristics, and, when grown in broth, the smooth cells were found to be autoagglutinating and able to switch into the non-agglutinating rough phenotype. The rough cells did not switch into the smooth phenotype under any growth conditions tested, indicating that the phase variation from the smooth to rough phenotype is irreversible or that the conditions for the reversible switch are still to be found. Smooth cells were hydrophobic and more adhesive compared to the hydrophilic rough cells, suggesting that the phase variation most probably involves one or several surface structures other than outer membrane proteins and lipopolysaccharides that were found to be similar in both types. Analysis of extracellular products produced by the 2 cell types indicated furthermore that a difference in enzymatic activities could exist. Both cell types were virulent for rainbow trout in an intramuscular challenge; thus, the distinct physiological characteristics of the phenotypes do not seem to be directly associated with virulence, when the body surface of the fish is disregarded. The results suggest that phase variation occurs in F. psychrophilum, but that the importance of the 2 phenotypes for the pathogenesis of the bacterium has still to be investigated.
Eva Högfors-Rönnholm; Tom Wiklund
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Diseases of aquatic organisms     Volume:  90     ISSN:  0177-5103     ISO Abbreviation:  Dis. Aquat. Org.     Publication Date:  2010 May 
Date Detail:
Created Date:  2010-07-05     Completed Date:  2010-08-17     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  8807037     Medline TA:  Dis Aquat Organ     Country:  Germany    
Other Details:
Languages:  eng     Pagination:  43-53     Citation Subset:  IM    
Laboratory of Aquatic Pathobiology, Department of Biology, Abo Akademi University, BioCity, Tykistökatu 6, 20520 Turku, Finland.
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MeSH Terms
Fish Diseases / microbiology
Flavobacterium / classification*,  physiology*
Oncorhynchus mykiss
Time Factors

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