Structural and functional analysis of the gene cluster encoding carotenoid biosynthesis in Mycobacterium aurum A+.

The fragment containing the carotenoid gene cluster from Mycobacterium aurum A+, a 3,3'-dihydroxy-isoneriatene and 3-monohydroxy-isoneriatene accumulator, has been sequenced and the exposed eight genes are organised in two operons. The function of three of these genes, a phytoene desaturase (crtI), a phytoene cyclase (crtY) and a beta-carotene desaturase (crtU), was demonstrated by complementation of M. aurum carotenoid mutants. The eight genes of the carotenoid cluster are highly homologous to other carotenoid gene clusters and thus this cluster is a candidate for its introduction into mycobacteria as a non-antibiotic reporter gene(s) as well as a source of new regulated promoters.