Conjugative transfer of broad host range plasmids to an acidobacterial strain, Edaphobacter aggregans.

The Acidobacteria phylum is of high ecological interest. Its members are ubiquitous and particularly abundant in soils but many are recalcitrant to cultivation in the laboratory. Thus, the ability of Acidobacteria to capture and maintain plasmids remains largely unexplored. In this work we tested the transfer and the stability of (i) the PromA plasmid pMOL98 and (ii) the IncQ plasmid pKT230 to the acidobacterial strain Edaphobacter aggregans DSM 19364. To this end quantitative conjugation assays were performed and transconjugants were scored for plasmid-borne antibiotic selection markers. The tested plasmids were transferred and maintained in the new host. Plasmid pMOL98 was more stable than pKT230 in Ed. aggregans in the absence of positive selection. Thus, from an ecological point of view, we have extended the host range of PromA and IncQ plasmids for the first time to an acidobacterial strain. Furthermore, we have uncovered the potential of Acidobacteria to capture as-yet-unknown plasmids and to foster the development of new cloning and expression systems for the exploitation of biotechnologically valuable soil resources.