Involved in DNA conjugation, at least in the recipient strain (PubMed:18554329). Secreted via the ESX-1 / type VII secretion system (T7SS) (By similarity). Loss of DNA conjugation when disrupted in recipient strain; strain still secretes EsxB (PubMed:18554329). DNA conjugation in M.smegmatis is unidirectional with distinct donor and recipient strains; mc(2)155 is a donor strain while MKD8 is a recipient strain. Mutations in a donor strain that alter DNA transfer do not always alter DNA transfer in a recipient strain. Belongs to the EspB family.