Renoz, François
[UCL]
Serratia symbiotica, one of most frequent symbiont found in aphids, is a valuable symbiont candidate for studying the evolution of bacterial mutualism in insects. Indeed, this bacterial symbiont species includes a wide variety of strains ranging from a free-living to intracellular lifestyles, being either facultative, either co-obligate partners for the host aphid. The main purpose of this work was to investigate how symbiotic bacteria form new associations and extend their influence in insect populations. A culture-dependent approach was used to decipher the microbial diversity hosted by several aphid species. Novel microbial partners of aphids were identified and several novel S. symbiotica strains were isolated. Genomic features displayed by S. symbiotica strain CWBI-2.3T that likely play a role in the establishment of symbiosis were scrutinized. Our analysis supports for the presence of many genes potentially involved in host interactions. We demonstrate that the aphid gut is a suitable environment for the multiplication of S. symbiotica whose does not induce immediate pathogenic effects and do not trigger the aphid immune defenses that were investigated. In addition, the symbiont is able to express a wide range of molecular effectors that are potentially required during the initial stages of host colonization. Finally, we highlight the existence of gut-associated S. symbiotica strains in wild aphids and ants populations, illustrating the extraordinary diversity and versatility of the symbiont. Although the symbiotic status of these extracellular S. symbiotica strains has not yet been clearly identified, it appears that both facultative and co-obligate intracellular strains are derived from free-living S. symbiotica strains that have been gradually domesticated by the host insect. In view of these results, S. symbiotica strains exhibiting a free-living capacity represent tremendous candidates to investigate the origins of bacterial mutualism in insects.
Bibliographic reference |
Renoz, François. Evolution of bacterial mutualism in insects: the case of Serratia symbiotica in aphids. (2017) |
Permanent URL |
http://hdl.handle.net/2078.1/195462 |