REGULATION OF ESCHERICHIA-COLI K5 CAPSULAR POLYSACCHARIDE EXPRESSION - EVIDENCE FOR INVOLVEMENT OF RFAH IN THE EXPRESSION OF GROUP-II CAPSULES

Expression of the Escherichia coli K5 antigen was used as a model syst em to study the role of known regulators of gene expression on product ion of group II capsules in E. coli. Only mutations in the rfaH gene h ad an effect on production of the K5 antigen, abolishing the expressio n of any detectable capsule at 37 degrees C. None of the mutations stu died induced capsule expression at 18 degrees C. A sequence, termed JU MPstart, found in group II capsule gene clusters and upstream of a num ber of polysaccharide biosynthesis genes in enteric bacteria is homolo gous to sequences found in RfaH regulated operons. This may indicate a common mode of regulation of these polysaccharide biosynthesis genes by RfaH.