Phenotypes, transcriptome, and novel biofilm formation associated with the ydcI gene

The ydcI gene has previously been shown to encode a DNA-binding protein involved with acid stress resistance and induced biofilm formation in a strain of Salmonella enterica serovar Typhimurium. In addition, characterisation of the ydcI gene in Escherichia coli and other bacteria demonstrated strikingly different tolerance for induced ydcI expression across Gram negative species. In this report, we investigated the conservation of these phenotypes across multiple strains of S. Typhimurium and E. coli, and we used RNA Seq to identify the transcriptome of the ΔydcI mutant compared to WT in S. Typhimurium and E. coli (to establish the YdcI regulon in each species). We constructed deletion mutants in each species based on the RNA Seq results and tested these mutants for the relevant ydcI-related phenotypes. Though no evidence for a role in these phenotypes was found via the RNA Seq deletion mutants, we found that the ydcI-induced biofilm in S. Typhimurium is formed independently of the major biofilm genes csgA and bcsA indicating a potentially novel type of biofilm formation.