A NOVEL COMPETENCE GENE, COMP, IS ESSENTIAL FOR NATURAL TRANSFORMATION OF ACINETOBACTER SP. STRAIN BD413

Acinetobacter sp, strain BD413 (= ATCC 33305), a nutritionally versati le bacterium, has an extremely efficient natural transformation system , Here we describe the generation of eight transformation-affected mut ants of Acinetobacter sp, strain BD413 by insertional mutagenesis. The se mutants were found by Southern blot analysis and complementation st udies to result from single nptII marker insertions at different chrom osomal loci, DNA binding and uptake studies with one mutant, T205, rev ealed that the transformation deficiency of this mutant results from a complete lack of DNA binding and, therefore, uptake activity, A novel competence gene essential for natural transformation, named comP, was cloned by complementation of mutant T205, The nucleotide sequence of comP was determined, and its deduced 15-kDa polypeptide displays signi ficant similarities to type IV pilins, Analysis of the ultrastructure of a transformation-deficient comP mutant and the transformation-compe tent wild-type strain revealed that both are covered with bundle-formi ng thin fimbriae (3 to 4 nm in diameter) and individual thick fimbriae (6 nm in diameter). These results provide evidence that the pilinlike ComP is unrelated to the piluslike structures of strain BD413. Taking all data into account, we propose that ComP functions as a major subu nit of an organelle acting as a channel or pore mediating DNA binding and/or uptake in Acinetobacter sp, strain BD413.