spro:N7E60_14645 K11903 type VI secretion system secreted protein Hcp | (GenBank) hcp-2; type VI secretion system effector Hcp-2 spro:N7E60_15540 K11900 type VI secretion system protein ImpC | (GenBank) tssC; type VI secretion system contractile sheath large subunit spro:N7E60_15535 K11901 type VI secretion system protein ImpB | (GenBank) tssB; type VI secretion system contractile sheath small subunit