INTEGRATION HOST FACTOR IS REQUIRED FOR 1,2-PROPANEDIOL-DEPENDENT TRANSCRIPTION OF THE COB PDU REGULON IN SALMONELLA-TYPHIMURIUM LT2/

We show that integration host factor (IHF) is required for the activat ion of transcription of the cobalamin biosynthetic (cob) and 1,2-propa nediol (1,2-PDL) utilization (pdu) operons in Salmonella typhimurium L T2. A lack of IHF affected transcription of the cob/pdu regulon in at least two ways. First, the level of the regulatory protein PocR was de creased in ihfB (formerly himD) mutants, as judged by Western blot ana lysis with polyclonal antiserum raised against PocR. Second, even when PocR was available, in the absence of IHF, PocR was unable to activat e transcription of cob/pdu in response to 1,2-PDL. This result suggest ed an additional role for IHF in PocR-dependent transcription activati on. Consistent with these findings, ihfB mutants of this bacterium wer e unable to use 1,2-PDL as a carbon or energy source.