Neisseria gonorrhoeae WS1 is a spontaneous pyocin (a bacteriocin produced by Pseudomonas aeruginosa)-resistant mutant of N. gonorrhoeae FA19 that produces a truncated lipooligosaccharide (LOS) and is nontransformable. The LOS specific mutation in WS1 was moved into a transformable background by transforming FA19 with chromosomal DNA from WSI (generating strain JWS-1), A clone (pJCL2) capable of restoring JWS-1 to wild-type LOS expression, as detected by its acquisition of reactivity with monoclonal antibodies and by its complemented sodium dodecyl sulfate-polyacrylamide gel electrophoresis profile, was isolated, Sequential unidirectional deletion and DNA sequence analysis of pJCL2 identified an open reading frame, designated lsi-7, that could complement the defect in JWS-1, Homology searches against various databases indicated that lsi-7 had homology with several Escherichia coli genes involved in the phosphorylation of sugars, lsi-7 is adjacent to the lsi-6 gene, another gene involved in LOS biosynthesis. Complementation studies using Salmonella typhimurium lipopolysaccharide mutants showed lsi-6 and lsi-7 to be gonococcal homologs of S, typhimurium rfaD and rfaE, respectively. Reverse transcriptase PCR analysis demonstrated that lsi-6 and lsi-7 are part of the same transcriptional unit.