A SERUM-SENSITIVE, SIALYLTRANSFERASE-DEFICIENT MUTANT OF NEISSERIA-GONORRHOEAE DEFECTIVE IN CONVERSION TO SERUM RESISTANCE BY CMP-NANA OR BLOOD-CELL EXTRACTS

A stable, sialyltransferase-deficient mutant of Neisseria gonorrhoeae strain F62 totally defective in CMP-NANA-dependent lipopolysaccharide (LPS) sialylation was isolated by insertion mutagenesis with transposo n Tn1545-Delta 3 and screened for unlabelled colonies following incuba tion with CMP-C-14-NANA. In contrast to the parental strain which beca me serum resistant on incubation with CMP-NANA or blood cell extracts, the mutant, JB1, remained serum sensitive. French press extracts of s train F62 catalysed LPS sialylation, but corresponding extracts of the mutant were inactive. Five LPS components were detected by SDS-PAGE i n the parental strain. Five components of the same M(r) were also foun d in the mutant. Th ree identical components were detected by Western blotting using MAb 3F11, which recognises the Gal beta 1-4GlcNAc group s in the conserved LPS components of F62 which can be sialylated. The mutant, JB1, is therefore deficient in the sialyltransferase that is e ssential for both LPS sialylation and conversion of serum-sensitive go nococci to serum resistance by either CMP-NANA or blood cell extracts. No evidence was obtained for an LPS sialylation pathway by blood cell extracts that is independent of CMP-NANA.