Involvement of the Salmonella recA-hydN genomic region in the nitric oxide-mediated signaling. Salmonella sv. Typhimurium A9 (mutant lacking a 15kB fragment spanning recA-hydN genes) formed more abundant biofilms, which were not responsive to treatment with nitric oxide donor molsidomine. Detachment of the wild type biofilms in response to molsidomine (A). Lack of response to molsidomine by the A9 mutant (B). Appearance of the biofilms formed by the A9 mutant and the wild type (C). Genomic context of the A9 deletion (D). Thick arrows are annotated ORF. Genes with putative functions in nitric oxide signaling are shaded grey.