Expression of K99 pilus of E. coli.

Different factors are involved in production and (or) detection of K99. They are modifications in plasmid contents of the strains, the size of capsular antigens, the quantity of K99 protein produced according to the culture media. We made a distinction between the strains which produced K99 on Minca medium without glucose (K99-C) and those which needed glucose for production on this medium (K99-GD). The K99-GD strains were able to use adonitol and most K99-C strains did not. With strains K99-C we showed that heavily capsulated colonies produced as much K99 than non capsulated colonies, but heavily capsulated ones were hardly detected with slide agglutination. According to the carbon substrate, differences were observed in K99 production. Mannose was a bad carbon source for K99 production, the synthesis of which was completely inhibited with K99-GD strains, but not with K99-C strains. Adonitol was a good substrate for detection of K99 from K99-GD strains. Measure of intracellular AMPc showed that there was non catabolite repression for K99 biosynthesis. In the opposite, high intracellular level of AMPc was correlated with a low production of K99. Plasmid contents of the strains indicated that most strains had one or two plasmids in the range of 50-70 megadaltons. Small differences in plasmids are sometimes correlated with modifications in the quantity of K99 produced. The main conclusions were that the distinctions that we proposed between K99-C and K99-GD could help understand the mechanisms of K99 production.(ABSTRACT TRUNCATED AT 250 WORDS)