Salmonella Typhimurium putative rspA gene plays crucial role in its pathogenesis

Abstract

Salmonella spp. are facultative anaerobic, Gram-negative, rod-shaped bacteria and belongs to the Enterobacteriaceae family. Salmonella enterica serovar Typhimurium becomes a model pathogen because of its ability to infect a wide range of hosts, along which its infection it causes millions of death worldwide. The emergence of multidrugresistant strains of S. Typhimurium catches the focus of many scientists, increasing the infection rate in different populations and becoming a challenge for antibiotic treatment. Although much has been known about Salmonella pathogenesis, the functional characterizations of certain genes are yet to be explored. rspA is one such gene with putative dehydratase function, and its role in pathogenesis is unknown. The upregulation of rspA gene inside macrophages (previous microarray report), led us to investigate its role in Salmonella pathogenesis. We generated the rspA knockout strain (by one-step gene inactivation method) and complement strain in S. Typhimurium 14028. Ex-vivo and in-vivo infectivity was looked at in Raw-264.7, THP-1, HT-29, Int-407 cell lines and Caenorhabditis elegans (C. elegans). The mutant was surviving better than WT-STM in all the cell lines and in the worm also. We found out that rspA gene has no role in bacterial growth in vitro and motility; rather, it is very important for intracellular survival and biofilm formation in bacteria. Deleting the rspA gene resulted in a hyper infectious phenotype and was more lethal to the C. elegans. The complementation was able to restore the phenotype significantly. Our study indicates that the rspA gene might be very important to regulate the pathogenesis of Salmonella in intracellular environment.