A CRTB HOMOLOG ESSENTIAL FOR PHOTOCHROMOGENICITY IN MYCOBACTERIUM-MARINUM - ISOLATION, CHARACTERIZATION, AND GENE DISRUPTION VIA HOMOLOGOUSRECOMBINATION

A gene essential for light-induced pigment production was isolated fro m the photochromogen Mycobacterium marinum by heterologous complementa tion of an M. marinum cosmid library in the nonchromogen Mycobacterium smegmatis. This gene is part of an operon and homologous to the Strep tomyces griseus and Myxococcus xanthus crtB genes encoding phytoene sy nthase, Gene replacement at this locus,vas achieved via homologous rec ombination, demonstrating that its expression is essential for photoch romogenicity. The ease of targeted gene disruption in this pathogenic Mycobacterium allows for the dissection of the molecular basis of myco bacterial pathogenesis.