The genes for erythritol catabolism are organized as an inducible operon in Brucella abortus

Erythritol utilization is a characteristic of pathogenic Brucella abortus s trains. The attenuated vaccine strain gig is the only Brucella strain that is inhibited by erythritol, so a role for erythritol metabolism in virulenc e is suspected. A chromosomal fragment from the pathogenic strain B. abortu s 2308 containing genes for the utilization of erythritol was cloned taking advantage of an erythritol-sensitive Tn5 insertion mutant. The nucleotide sequence of the complete 7714 bp fragment was determined. Four ORFs were id entified in the sequence. The four genes were closely spaced, suggesting th at they were organized as a single operon (the ery operon), The first gene (eryA) encoded a 519 aa putative erythritol kinase, The second gene (eryB) encoded an erythritol phosphate dehydrogenase, The function of the third ge ne (eryC) product was tentatively assigned as D-erythrulose-1-phosphate deh ydrogenase and the fourth gene (eryD) encoded a regulator of ery operon exp ression. The operon promoter was located 5' to eryA, and contained an IHF ( integration host factor) binding site. Transcription from this promoter was repressed by EryD, and stimulated by erythritol. Functional IHF was requir ed for expression of the operon in Escherichia coli, suggesting a role for IHF in its regulation in a. abortus. The results obtained will be helpful i n clarifying the role of erythritol metabolism in the virulence of Brucella spp.