SYNTHESIS OF THE K5 (GROUP-II) CAPSULAR POLYSACCHARIDE IN TRANSPORT-DEFICIENT RECOMBINANT ESCHERICHIA-COLI

The genes directing the expression of group II capsules in Escherichia coli are organized into three regions. The central region 2 is type s pecific and thought to determine the synthesis of the respective polys accharide, whilst the flanking regions 1 and 3 are common to all group II gene clusters and direct the surface expression of the capsular po lysaccharide. In this communication we analyze the involvement of regi on 1 and 3 genes in the synthesis of the capsular KS polysaccharide. R ecombinant E. coli strains harboring all KS specific region 2 genes an d having various combinations of region 1 and 3 genes were studied usi ng immunoelectron microscopy. Membranes from these bacteria were incub ated with UDP[C-14]GlcA and UDPGlcNAc in the absence or presence of KS polysaccharide as an exogenous acceptor. It was found that recombinan t strains with only gene region 2 did not produce the K5 polysaccharid e. Membranes of such strains did not synthesize the polymer and did no t elongate K5 polysaccharide added as an exogenous acceptor. An involv ement of genes from region 1 (notably kpsC and kpsS) and from region 3 (notably kpsT) in the K5 polysaccharide synthesis was apparent and is discussed.