Spreading the news about the novel conjugation mechanism in Streptomyces bacteria

The hallmark of mycelial spore-forming bacteria of the genus Streptomyces is their prolific production of antibiotics and other bioactive secondary metabolites as part of a complex morphological and physiological developmental program. They are further distinguished by a conjugation mechanism that differs substantially from the single-strand mode of DNA transfer via Type IV secretion, which is exhibited by numerous unicellular Gram-negative and Gram-positive bacteria. At the crux of the novel intermycelial transfer event in Streptomyces spp. is a membrane pore composed of a single plasmid protein (TraB), which also functions as an FtsK-like DNA pump driven by the energy of ATP hydrolysis. TraB binds to specific 8-mer repeats within the non-coding clt plasmid transfer locus and the DNA is then translocated intercellularly in double-strand form. TraB also translocates chromosomal DNA most likely by binding to 8-mer clc sequences (clt-like chromosomal sequences) distributed throughout streptomycete chromosomes. In the recipient, plasmids are dispersed through septal crosswalls apparently by a multiprotein complex comprising TraB and plasmid Spd proteins. Continued rounds of such intramycelial spreading distribute plasmids well beyond the initial entrance point during the time prior to cell differentiation and sporulation.