pKjK5 in an anaerobic polymicrobial bioreactor
While most studies on microbial antibiotic resistance have been done with single strains or co-cultures, we know that bacteria naturally live in multi-species communities where they interact with one another. Interspecies interactions such as horizontal gene transfer (HGT) are key factors in the evolution and spread of antibiotic resistance genes and there is thus a need to further investigate how resistance plasmids acquired through conjugation affect the dynamics and composition of more complex communities and what taxonomic barriers the plasmids might encounter as they invade a community.  In this study, we experimentally assess the dynamics and reach of HGT coupled to antimicrobial resistance in a polymicrobial community setting. Using a bacterial community derived from a human fecal sample and simulating its original environmental conditions, we assessed community composition after experimental exposure to antibiotics with and without the presence of a donor strain carrying a conjugative plasmid conferring resistance against antibiotics and the concomitant spread of this conjugative plasmid in the community. Our results demonstrated that the temporal development of structure and composition of the total bacterial community varied between control treatments (free of plasmid) and treatments where the donor carrying the conjugative plasmid pkjk5 was introduced. The plasmid pkjk5 was transferred to rare members of the polymicrobial community but notably it didn't invade one the most abundant Gram positive representatives. These results expand our understanding of how natural bacterial communities dynamics are impacted during antibiotic treatments and the influence of a conjugative plasmid in that development. Key words: antibiotic resistance, antibiotic resistance genes, horizontal gene transfer, conjugation, plasmid, microbial ecology, polymicrobial communities, gut microbiota, continuous culture, anaerobic.