Genetic analysis of microcin H47 antibiotic system.

The microcin H47 genetic determinants span a DNA region of ca. 10 kb and represent the first description of an enterobacterial antibiotic system located in the chromosome of the producing strain. Transcriptional and translational fusions to lacZ showed a complex transcriptional organization of the microcin H47 system. Complementation tests identified six genes that are necessary for the production of the antibiotic; the products of two of them are involved in the export of microcin to the extracellular medium. The immunity determinant was located in an 0.8-kb DNA fragment. There is a putative "silent region" of ca. 3 kb inside the system that could not be clearly related to any antibiotic function. Protein products were identified and assigned to three production genes and also to a gene from the silent region.