Temperature-dependent expression of conjugation pili by IncM plasmid-harbouring bacteria: identification of plasmid-encoded regulatory functions.

摘要: A 1,3 kb DNA fragment of the IncM plasmid R446, if cloned in a multicopy plasmid, inhibits trans expression conjugation pili by plasmid-harbouring host bacteria as indicated their insensitivity to pilus-dependent bacteriophage phi M (Iml, M-mediated lysis). Determination nucleotide sequence this fragment, introduction deletions an analysis transposon insertions reveal two determinants, imlA and imlB, responsible for Iml phenotype. stretch 80 bp containing about 450 adjacent comprising together, bring inhibition typical at 30 degrees C. The transposable promoter probe construction respective lacZ fusions indicate transcription complementary strands vivo overlapping region imlB. Moreover, reporter genes discloses temperature-dependent imlA-imlB-region one direction. particular subfragment 1.3 plasmid-derived does not inhibit pilus C but stimulates formation 42 give rise untypical sensitivity addition Other subfragments vital interferences with cells. putative nature determinants interfering normal is discussed.