Expression of an Escherichia coli flagellin gene, hag48, in the presence of a Salmonella H1-repressor.

An Escherichia coli K12 flagellin gene, hag48, was found to be expressed in the presence of the Salmonella rh1 gene product. The strains which had hag48 on a chromosome or on an F' factor were constructed from strains H2-e,n,xon-off rh1+ and fixed H2-e,n,xon rh1+ in which rh1+ is cotranscribed with H2 in its "on" state. Motility of these strains in semisolid medium was inhibited by anti-H48 serum and motile clones (swarms) that escaped from it were hag mutants in case of the hag48 e,n,xon-off strain tested. H48 flagellin was detected by electrophoresis, though its amount was less than e,n,x flagellin, from all the strains that were nonmotile in the presence of anti-H48 serum.