The lgtABCDE Gene Cluster, Involved in Lipooligosaccharide Biosynthesis in Neisseria gonorrhoeae , Contains Multiple Promoter Sequences

Abstract

ABSTRACT Biosynthesis of the variable core domain of lipooligosaccharide (LOS) in Neisseria gonorrhoeae is mediated by glycosyl transferases encoded by lgtABCDE . Changes within homopolymeric runs within lgtA , lgtC , and lgtD affect the expression state of these genes, with the nature of the LOS expressed determined by the functionality of these genes. However, the mechanism for modulating the amount of multiple LOS chemotypes expressed in a single cell is not understood. Using mutants containing polar disruptions within the lgtABCDE locus, we determined that the expression of this locus is mediated by multiple promoters and that disruption of transcription from these promoters alters the relative levels of simultaneously expressed LOS chemotypes. Expression of the lgtABCDE locus was quantified by using xylE transcriptional fusions, and the data indicate that this locus is transcribed in trace amounts and that subtle changes in transcription result in phenotypic changes. By using rapid amplification of 5′ cDNA ends, transcriptional start sites and promoter sequences were identified within lgtABCDE . Most of these promoters possessed 50 to 67% homology with the consensus gearbox promoter sequence of Escherichia coli .