Fig. 3.
Identification of T6S-dependent antibacterial effectors and cognate immunity proteins in B. fragilisN. (A) Secretome profiling reveals two candidate effectors in B. fragilisN. Proteins secreted by B. fragilisN in a T6S-dependent manner (Dataset S1, Table S4) are mapped onto its T6SS locus (red, known T6SS components; blue, candidate effectors). (B) Candidate E/I pairs protect against T6S-mediated killing. B. fragilisN donor cells were grown in contact with B. fragilisN tssC recipient cells carrying deletions of genes encoding the E/I pairs. (C) Expression of effector genes causes T6S-mediated killing of recipient cells lacking cognate immunity genes. B. fragilisN donor cells were grown in contact with E/I mutant recipient cells expressing immunity genes or carrying an empty vector. (D and E) B. thetaiotaomicron (D) and B. vulgatus (E) are protected from B. fragilisN T6S by heterologous expression of immunity genes. Recipient species carry an empty vector or constitutively express B. fragilisN immunity genes. In all graphs, *P < 0.05. Error bars indicate ± SD (n = 2; representative of three independent trials).