Salmonella enterica serovar Typhimurium is a gastrointestinal pathogen that overcomes colonization resistance of the gut microbiota and invades epithelial cells. Salmonella´s invasion of eukaryotic cells is driven by virulence factors and motility.
In this study, we dissect the role of cyclic di-GMP, a bacterial secondary messenger in the regulation of motility of a peritrichously flagellated bacterium such as Salmonella.
A genetic dissection of the c-di-GMP signaling network identified three GGDEF domain proteins STM2672, STM4551 and STM1987 as key di-guanylate cyclases involved in downregulation of motility in the background of a yhjH deletion background.
YhjH is a key EAL domain protein provocking an upregulation of motility.
These di-guanylate cyclases distinctively inhibit motility through the c-di-GMP receptors YcgR and/or the cellulose synthase BcsA. While STM2672 selectively inhibits motility through YcgR, STM1987 inhibits motility through BcsA and STM4551 serves both receptors.
Regulation of motility under our experimental conditions is independent from the major biofilm regulator CsgD.
We can conclude that regulation of motility in Salmonella Typhimurium is differentially regulated by the c-di-GMP signaling network through the affection of flagellar functionality and stimulation of cellulose biosynthesis.