comH, a novel gene essential for natural transformation of Helicobacter pylori

Helicobacter pylori is naturally competent for transformation, but the DNA uptake system of this bacterium is only partially characterized, and nothin g is known about the regulation of competence in H. pylori. To identify oth er components involved in transformation or competence regulation in this s pecies, we screened a mutant library for competence-deficient mutants. This resulted in the identification of a novel, Helicobacter-specific competenc e gene (comH) whose function is essential for transformation of H. pylori w ith chromosomal DNA fragments as web as with plasmids. Complementation of c omH mutants in hans completely restored competence. Unlike other transforma tion genes of H. pylori, comH does not belong to a known family of ortholog ous genes. Moreover, no significant homologs of comH were identified in cur rently available databases of bacterial genome sequences. The comH gene cod es for a protein with an N-terminal leader sequence and is present in both highly competent and less-efficient transforming H. pylori strains. A comH homolog was found in Helicobacter acinonychis but not in Helicobacter felis and Helicobacter mustelae.