loss-of-function in surface motility and biofilm formation by Rm1021 and GR4.
fadD knock-out mutation could lead to the accumulation of as yet an uncharacterized fatty acid-related compound whose synthesis is not under iron control. This compound promotes surface motility of both Rm1021 and GR4 even in the absence of Rhb1021 and thus negatively interferes with biofilm development. Impairment in biofilm formation caused by fadD mutation is more drastic in the GR4 strain in that it affects not only the thickness of biofilms, but also abolishes the development of the characteristic sponge-like structure of biofilms formed under iron-replete conditions. Comparisons of biofilms are made relative to the corresponding parent strain.