Neisseria subflava Type 6 Secretion System competition with bacterial and fungal species

The aim of this study was to assess whether a Type VI Secretion System (T6SS) present in the commensal, non-pathogenic Neisseria subflava strain KU1003-01 plays a role in competition between these bacteria and other commensal and pathogenic Gram-negative microorganisms and the yeast Candida albicans. Using an overlap extension PCR strategy, the core T6SS gene encoding membrane protein TssM was knocked out for N. subflava strain KU1003-01. Co-culture competition assays were conducted with either the N. subflava or N. subflava tssM knock-out strains as the attackers and N. gonorrhoeae strain NCCP11945, N. subflava strain KU1003-02, or C. albicans strain 3153 as the targets. There was a significant difference in recoverable target cell CFUs observed following co-culture with the T6SS knock-out strain in comparison to the parent strain. TssM has been identified as critical to T6SS function for a number of species, and our findings indicate that the T6SS in N. subflava contributes to competition with these other species.