[S1-4] Understanding behaviors of plasmids in natural environments using single-cell-level analyses
Plasmids can be transmitted between different bacterial cells and are important genetic elements because they are spreading various genes, including drug resistance genes. However, it remains unclear when and which plasmids are transmitted from one bacterium to another in nature. The objective our study is to understand the behaviors of different plasmids in the environment. We successfully obtained variety of conjugative plasmids from soil, sediment in rivers and lakes, sewage treatment plants, and livestock manure in various sites of Japan. There were PromA group plasmids as many as IncP/P-1 group plasmids, which are known to be widely distributed in the environment. Next, a GFP gene was inserted into a PromA group plasmid and then, the host ranges of different PromA plasmids were compared using a model bacterial community and flow cytometry and cell sorter. As a result, PromA group plasmids showed broad host ranges transferring among different class bacteria. Notably, transconjugants of each plasmid was different even if they belong to the same PromA group plasmid. Since there was little information on the original host of PromA group plasmid (i.e., the natural host), their natural host were identified by droplet digital PCR and sorting methods. As a result, nine operating taxonomic units (OTU) were obtained as candidates of natural hosts of PromA plasmid.