Fig 4.

Inactivation of comEC in A. baumannii abolishes twitching-like motility and natural transformation competence. A. baumannii isolates 07-095 and 07-102 were transformed on motility plates as described in the text using chromosomal DNA derived from A. baumannii ATCC 17978 comEC::Km to generate comEC mutants 07-095 comEC::Km and 07-102 comEC::Km, respectively. (A) Subsequently, both mutants and their respective parental strains were inoculated into motility medium as described in the text. Motility at the interphase was observed with the parental strains (arrowheads) but not with the mutant derivatives. (B) To prove an involvement of comEC in natural competence, 07-095 comEC::Km and its parental strain were incubated on motility plates with or without plasmid pWH1266 conferring resistance to ampicillin and tetracycline. The bacteria were then floated off the motility plates, and after adjustment of optical densities, the bacteria were plated on LB agar plates containing 100 μg/ml of ampicillin to select for transformants. While strain 07-095 was readily transformable, its comEC-inactivated derivative was not.