Functional analysis of the group A streptococcal luxS/AI-2 system in metabolism, adaptation to stress and interaction with host cells
The luxS/AI-2 signaling pathway has been reported to interfere with important physiological and pathogenic functions in a variety of bacteria. In the present study, we investigated the functional role of the streptococcal luxS/AI-2 system in metabolism and diverse aspects of pathogenicity including the adaptation of the organism to stress conditions using two serotypes of Streptococcus pyogenes, M1 and M19.
Results: Exposing wild-type and isogenic luxS-deficient strains to sulfur-limited media suggested a limited role for luxS in streptococcal activated methyl cycle metabolism. Interestingly, loss of luxS led to an increased acid tolerance in both serotypes.
Accordingly, luxS expression and AI-2 production were reduced at lower pH, thus linking the luxS/AI-2 system to stress adaptation in S. pyogenes.
luxS expression and AI-2 production also decreased when cells were grown in RPMI medium supplemented with 10% serum, considered to be a host environment-mimicking medium. Furthermore, interaction analysis with epithelial cells and macrophages showed a clear advantage of the luxS-deficient mutants to be internalized and survive intracellularly in the host cells compared to the wild-type parents.
In addition, our data revealed that luxS influences the expression of two virulence-associated factors, the fasX regulatory RNA and the virulence gene sibA (psp).
Conclusions: Here, we suggest that the group A streptococcal luxS/AI-2 system is not only involved in the regulation of virulence factor expression but seems to provide the pathogen a tool allowing to thrive under conditions often encountered during infections.
Author: Maria Siller, Rajendra P. Janapatla, Zaid A. Pirzada, Christine Hassler, Daniela Zinkl and Emmanuelle Charpentier
Credits/Source: BMC Microbiology 2008, 8:188
Published on: 2008-10-30
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