GENES REQUIRED FOR EXTRACELLULAR SECRETION OF ENTEROTOXIN ARE CLUSTERED IN VIBRIO-CHOLERAE

Pleiotropic transposon insertion mutants of Vibrio cholerae that are u nable to secrete enterotoxin, HA/protease and chitinase through the ou ter membrane have been isolated. The gene, epsM, responsible for compl ementation of two of the Tn5 insertion mutations was sequenced. It enc odes a putative cytoplasmic membrane protein of 18.5 kDa that exhibits similarity to proteins required for extracellular secretion of pullul anase, pectate lyase or elastase in other Gram- bacteria. It is presen t on a 15-kb DNA fragment from the V. cholerae genome, containing the epsE gene that was previously shown to be required for secretion of ch olera toxin [Sandkvist et al., Gene 123 (1993) 81-86]. Partial reading frames flanking epsM also demonstrated similarity to genes required f or extracellular secretion of pullulanase in Klebsiella oxytoca.