Provided are recombinant DNA molecules that do not occur in nature encoding an O-acetyltransferase, vectors that direct expression of an O-acetyltransferase, recombinant host cells which express an O-acetyltransferase, methods for recombinant production of an O-acetyltransferase, methods for acetylating capsular polysaccharides, especially those of a Serogroup A Neisseria meningitidis using a recombinant O-acetyltransferase, and immunogenic compositions comprising the acetylated capsular polysaccharide.
ACKNOWLEDGMENT OF FEDERAL RESEARCH SUPPORT
 This invention was made, at least in part, with funding from the National Institutes of Health (Grant No. AI40247) and the Department of Energy (Grant No. DE-FG02-93ER20097). Accordingly, the United States Government has certain rights in this invention.