Antigen 43, a phase-variable bipartite outer membrane protein, determines colony morphology and autoaggregation in Escherichia coli K-12.

The product controlling colony form variation and autoaggregation in Escherichia coli K-12 (the flu gene product) has been identified as the phase-variable, bipartite, outer membrane protein, termed antigen 43 (Ag43). Identification is based: (i) on complete correlation in authentic flu variants between colony morphology/autoaggregation and Ag43 expression as determined by colony and Western immunoblotting and immunofluorescence microscopy; and (ii) on the use of a specific probe to map the gene encoding Ag43 to a position (min 43) on the E. coli chromosome previously established for flu.