HM2-phage resistant solventogenic Clostridium saccharoperbutylacetonicum N1-4 shows increased exopolysaccharide production

During the history of the solventogenic clostridia fermentation industry, bacteriophages have been a recurrent problem. This study reports that HM2, a lytic bacteriophage for solventogenic Clostridium saccharoperbutylacetonicum N1-4 (N1-4), has a genome size of 17 470 bp with 22 open reading frames, including replication, lysis, integration and structural modules. To understand HM2 infection and resistance in N1-4, bacteriophage insensitive mutants (BIMs) were isolated and characterized. These eight independent BIMs included four adsorption mediated and four non-adsorption types. Adsorption mediated BIMs had increased exopolysaccharide (EPS) production and decreased attachment of HM2 to the cell surface. Non-adsorption mediated BIMs had a moderate increase in EPS production, which did not affect HM2 attachment. Absorption mediated BIMs had reduced fermentation performance, whereas the non-absorption mediated BIMs were indistinguishable from N1-4. Consequently, non-adsorption mediated BIMs would be more useful in a fermentation since they couple good fermentation performance with phage resistance.