Regulation of the lipopolysaccharide-specific sialyltransferase activity of gonococci by the growth state of the bacteria, but not by carbon source, catabolite repression or oxygen supply

The enzyme sialyltransferase (STase) of Neisseria gonorrhoeae is a major pa thogenicitiy determinant. Using a refined method for assaying the STase act ivity, the Km for CMP-NANA was shown to be 14 +/- 2 mu M, higher than that reported previously. Rates of sialylation by Nonidet extracts, prepared und er conditions that optimise solubilisation of the membrane-bound enzyme, we re 6 to 20 nmol of NANA transferred from CMP-C-14-NANA onto isolated lipopo lysaccharide/min./mg of extracted protein, far higher than the previously r eported rates of less than 1 nmol of NANA transferred/min./mg of extracted protein. Gonococci grew more slowly with lactate or pyruvate than with gluc ose as the carbon source. Although growth with a mixture of limiting concen trations of both glucose and lactate was biphasic, diauxic growth was also found in the control culture supplied with glucose alone. The growth rate i n the presence of lactate alone was slower than with glucose. The growth ra te increased slightly relative to the glucose culture when both substrates were available; lactate was consumed more rapidly than glucose. Higher STas e activities were found in bacteria harvested in the exponential than in th e stationary phase of aerobic growth: the activity in aerated cultures was higher than those of oxygen-limited or anaerobic cultures. Similar STase ac tivities were found in bacteria that had been grown with glucose, lactate o r pyruvate as the carbon and energy source. Sialyltransferase synthesis is essentially constitutive: it is not regulated by glucose repression or by i nduction by lactate or anaerobiosis.