Role of toxR on survival strategies of Vibrio cholerae O1 El Tor
Abstract number: P1163
Valeru S., Abd H., Sandström G.
Objectives:Vibrio cholerae, the causative agent of diarrhoeal disease cholera, utilises different survival strategies in aquatic environments. The bacterium can survive as free-living or in association with zooplankton and under starvation it can build biofilm and rugose colonies. V. cholerae expresses cholera toxin and toxin-coregulated pilus as the main virulence factors, which are co-regulated by a transcriptional regulator toxR.
Aim of the current study was to investigate role of toxR gene on survival of V. cholerae O1 El Tor under starvation or in association with the free-living amoeba Acanthamoeba castellanii.
Methods: Starvation survival test, rugose switching test, biofilm analysis, analysis of protein expression, analysis of toxR expression and bacteria-amoeba association assay.
Results: The results showed that toxR mutant can shift to rugose colony morphology in response to nutrient starvation characterised by wrinkled colony morphology, which shows increased biofilm formation and enhanced survival under specific conditions such different media and different temperatures. The toxR mutant strain shows high frequency of rugose switching at stationary phase when compared with wild-type V. cholerae strains. Immunoblot analysis showed that expression of Omp T was increased in rugose strains and Omp U seemed to be reduced.
The association assay of the bacteria with amoebae showed that presence of A. castellanii enhanced growth and survival of V. cholerae wild-type and toxR mutant to 100 fold at day 10. In comparison, growth of bacteria decreased 10000 fold from day 4 in absence of the amoebae. Despite A. castellanii grew well in absence of wild-type and toxR mutant bacterial strains, presence of the each bacterial strain did not inhibit growth of the amoebae.
Conclusions: The variation in expression of outer membrane proteins seem to play an important role in V. cholerae O1 El Tor (strain 1552) rugose and smooth switching. Rugose to smooth switching mechanism in V. cholerae may be toxR dependent, and the toxR gene is also important for the survival of V. cholerae in starvation conditions. A. castellanii enhanced growth of both wild-type and toxR mutant V. cholerae strains indicating that toxR has no affect on the interaction of V. cholerae with A. castellanii and that the bacteria are adapted to survive with the amoebae possibly in the aquatic environments.
|Session name:||Abstracts 20th European Congress of Clinical Microbiology and Infectious Diseases|
|Location:||Vienna, Austria, 10 - 13 April 2010|
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