The PulE ATPase is required for twitching motility and DNA donation during Thermus thermophilus transjugation

Abstract

Thermus thermophilus can acquire DNA through natural competence and through transjugation, a mechanism that involves a two-step process of DNA secretion (push) and DNA internalization (pull) between mating cells of related species. The natural competence apparatus (NCA) is required in the recipient mate for the pull step. However, how the DNA gets out of the donor cell is only partially known. The putative DNA translocase TdtA, encoded in mobile genetic element ICETh1 of T. thermophilus HB27, was shown to be required for DNA donation (Blesa et al. 2017a). This ring-shaped hexameric ATPase binds to the membrane and likely interacts with yet unknown secretory components that allow the extrusion of DNA through the membrane, so a genetic screening to identify additional putative secretory components was executed. Here, we describe that mutants in gene TT_C1844, encoding a putative AAA-ATPase thereafter named PulE, do not synthesize the recently described “narrow” type 4 pili required for twitching motility and made of major PilA5 pilin. Concomitantly, pulE mutants were also defective in DNA dotation during transjugation, suggesting a role of narrow pili in the donation process. However, single pilA5 null mutants were still functional as DNA donors in transjugation experiments, so we conclude that the need for PulE in transjugation is independent from its role in narrow pili synthesis and twitching motility.