The RNA polymerase gene specificity factor sigma 54 is required for homogeneous non-planktonic growth of uropathogenic Escherichia coli

The canonical function of a bacterial sigma ({sigma}) factor is to determine the gene specificity of the RNA polymerase (RNAP). In several diverse bacterial species, the {sigma}54 factor uniquely confers distinct functional and regulatory properties on the RNAP. A hallmark feature of the {sigma}54-RNAP is the obligatory requirement for an activator ATPase to allow transcription initiation. The genes that rely upon {sigma}54 for their transcription have a wide range of different functions suggesting that the repertoire of functions performed by genes, directly or indirectly affected by {sigma}54, is not yet exhaustive. By comparing the non-planktonic growth properties of prototypical enteropathogenic, uropathogenic and non-pathogenic Escherichia coli strains devoid of {sigma}54, we uncovered {sigma}54 as a determinant of homogenous non-planktonic growth specifically in the uropathogenic strain. Notably, bacteria devoid of individual activator ATPases of the {sigma}54-RNAP do not phenocopy the {sigma}54 mutant strain. It seems that {sigma}54s role as a determinant of homogenous non-planktonic growth represents a putative non-canonical function of {sigma}54 in regulating genetic information flow.