THE CAPSULE AND O-ANTIGEN IN VIBRIO-CHOLERAE-O139 BENGAL ARE ASSOCIATED WITH A GENETIC REGION NOT PRESENT IN VIBRIO-CHOLERAE-O1

Vibrio cholerae O139 Bengal, although closely related to V. cholerae O 1 El Tor, produces a polysaccharide capsule and has a distinct O antig en. We have identified a chromosomal region of at least II kb, as defi ned by three TnphoA mutations, that is required for the expression of both polysaccharides. Electron microscopy and sodium dodecyl sulfate-p olyacrylamide gel electrophoresis show that these TnphoA mutants have lost the abilities both to express capsule and to produce lipopolysacc haride beyond the core oligosaccharide. Reactivity with O139 typing se rum and resistance to serum are also lost in the mutants, DNA probes f or this region do not hybridize with O1 V. cholerae but do react with other vibrios, implying that the region was recently acquired.