SEARCH OF CHROMOSOMAL GENES INVOLVED IN MICROCIN J25 PRODUCTION

POMARES, M. FERNANDA; SALOMÓN, RAÚL A.; FARÍAS, RICARDO N; VINCENT, PAULA A

Pinamar-Argentina

Congreso; XLIReunión Anual de la Sociedad Argentina de Investigaciones en Bioquímica y Biología Molecular; 2005

Sociedad Argentina de Investigaciones en Bioquímica y Biología Molecular

Microcin J25 (MccJ25) is a plasmid-encoded, 21-amino-acid, antibacterial peptide produced by Escherichia coli. We have developed a system for identifying putative chromosomal genes involved in microcin synthesis or regulation. We transformed an E. coli  MccJ 5 sensitive  host with two plasmids, one of the plasmid bears genes required for microcin production. This construction is lethal for cells since it lacks the immunity gene and the other plasmid, a temperature-sensitive replicon that carries the MccJ25 immunity gene mcjD cloned. When shifted double transformants to 42ºC, the thermosensitive immunity plasmid was lost and, the only cells expected to survive were those having a chromosomal or a plasmid mutation lowering or abolishing microcin production. One chromosomal mutant was selected for further study. The mutation abolished microcin production. It was mapped to the lrp gene, encoding an E. coli global transcriptional regulator. Most likely, the lrp gene product acts as a positive regulator at the transcription level.