VINCENT Paula Andrea
congresos y reuniones científicas
Conferencia; ASM Conference on Mechanisms of Interbacterial Cooperation and Competition; 2017
BackgroundDistinctive microbial communities can be found at different plant structures (i.e. roots, stems and leaves) and it is expected that a functional basis underlays those specific associations. Even though there is considerable evidence that microbial communities associated with plants play a key role in the plant physiology, it is not trivial no manipulate those communities to obtain the desired effect. In order to gain some insight into the sugarcane microbiome composition and function, we isolated bacteria from this niche and evaluated bacterial interactions between members of the community. MethodsSugarcane endophytes were isolated by sampling plant stems with a cork borer, grinding plant tissue in a sterile mortar followed by resuspension in saline solution and plating in a culture medium containing salts, aminoacids and sucrose. After 5 days of incubation at 30° C, isolates were selected based on differential colony morphotypes and growth rates. 16S rDNA sequencing allowed the selection of a subset of phylogenetically different isolates for pairwise co-cultures on the same solid medium used for bacterial isolation. Microbial interactions were followed in time and interactions including growth promotion, growth inhibition, pigment production and colony morphology changes were documented. As an initial approach to elucidate the chemistry behind some interactions, we replaced one of the sugarcane isolates in the co-culture assay for the enterobacterium Escherichia coli. If the interaction was mimicked, then we used E. coli mutants defective in the production of known secreted metabolites. ResultsSeveral sugarcane endophytic isolates belonging to different genera showed at least one type of microbial interaction in the co-culture assay. We documented growth-inhibiting interactions, commensal and mutualistic growth promotion interactions, interactions affecting colony morphology and pigment production and an unanticipated interaction consisting in growth inhibition of one of the isolates in the immediate proximity of the two isolates but growth promotion at a distal position. The latest interaction involved the enterobacterium Pantoea dispersa. When P. dispersa was replaced in the co-culture assay with E. coli, the growth promoting effect was mimicked but the inhibitory phenotype was not reproduced. Interestingly, the E. coli growth promoting effect was lost when a strain impaired in the siderophore enterobactin synthesis was used. ConclusionsNumerous endophytic isolates showed the ability to interact with other members of the microbial community in several ways. One type of interaction stood out from the rest since it showed microbial inhibition when the two isolates were in close proximity but growth promotion when they were distant from each other. Preliminary data suggest that the growth-promoting phenotype might be mediated by a siderophore.