Abstract
Communication between species from different kingdoms may be as important as intra-kingdom communication. It has recently been confirmed that co-existing bacteria and phytoplankton in aquatic ecosystems do cross-talk. This study examined the signs of possible cross signalling between V. harveyi, one of the predominant bacterial species of the marine ecosystem and a dominant diatom species, S.marinoi, to understand communication over species borders. It is known that V.harveyi employ quorum sensing for cell-to-cell communication, bioluminescence (luxR), and the regulation of the virulence gene (vhp, chiA). Former studies have also shown, this kind of interactions being disrupted by compounds secreted by a few algal species existing in the aquatic ecosystem. We investigated the QS communication by quantifying the expression levels of virulence regulator luxR and virulence factors metalloprotease (vhp) and chitinase (chiA) in four different V. harveyi strains grown in the presence of S. marinoi strain. Results obtained in this study indicate that quorum sensing was activated in strains of V. harveyi analysed but did not regulate the expressions of vhp and chiA virulence factors. This observation suggests that the existence of S. marinoi did not interfere with the QS behaviour of V. harveyi and its interaction with marine diatom; it may be due to the commensalism relationship.
Highlights
In aquatic ecosystems, algae and bacteria coexist together, and there are many interactions between them, which are of particular interest to marine ecology.[1,2,3,4] Such interactions influence the physiology of these organisms, alter ecological and biogeochemical events, and shape the diversity of microbial communities in the ecosystem.[5]
This experiment confirmed that the microscopic counts of S. marinoi in the presence of Vibrio corresponded to the growth curve without bacteria present, and plate counts of Vibrio wild type strain BB120 in the presence of S. marinoi were similar to the counts in the absence of the diatom
A specificity test of the PCR primers used for amplifying rpoA, luxR, vhp, chiA genes in Vibrio BB120 genomic DNA and DNA from axenic S. marinoi, as templates for PCR, showed no bands for S. marinoi when PCR products were resolved on an agarose gel
Summary
Algae and bacteria coexist together, and there are many interactions between them, which are of particular interest to marine ecology.[1,2,3,4] Such interactions influence the physiology of these organisms, alter ecological and biogeochemical events, and shape the diversity of microbial communities in the ecosystem.[5]. QS modulates gene expression, essential for bacterial cell development, survival and pathogenicity.[13,14] The successful colonization and invasion of host by the pathogenic bacteria known to be mediated by QS.[13,15,16,17,18] QS has numerous influences on bacterial physiology and function as well as promotes contact-mediated communication with their symbionts.[7]
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