Genetic determinants in Salmonella enterica serotype Typhimurium required for overcoming stressors in the host environment

Abstract

Salmonella enterica serovar Typhimurium (S. Typhimurium), a non-typhoidal Salmonella (NTS), result in a range of diseases, including self-limiting gastroenteritis, bacteremia, enteric fever, and focal infections representing a major disease burden worldwide. There is still a significant portion of Salmonella genes whose functional basis to overcome host innate defense mechanisms, consequently causing disease in host, largely remains unknown. Here, we have applied a high-throughput transposon sequencing (Tn-seq) method to unveil the genetic factors required for the growth or survival of S. Typhimurium under various host stressors simulated in vitro. A highly saturating Tn5 library of S. Typhimurium 14028s was subjected to selection during growth in the presence of short chain fatty acid (100 mM propionate), osmotic stress (3% NaCl) or oxidative stress (1 mM H2O2) or survival in extreme acidic pH (30 min in pH3) or starvation (12 days in 1X PBS). We have identified an overlapping set of 339 conditionally essential genes (CEGs) required by S. Typhimurium to overcome these host insults. Interestingly, entire eight genes encoding F0F1-ATP synthase subunit proteins were required for fitness in all five stresses. Intriguingly, total 88 genes in Salmonella pathogenicity island (SPI), including SPI-1, SPI-2, SPI-3, SPI-5, SPI-6 and SPI-11 are also required for fitness under the in vitro conditions evaluated in this study. Additionally, by comparative analysis of the genes identified in this study and the genes previously shown to be required for in vivo fitness, we identified novel genes (marBCT, envF, barA, hscA, rfaQ, rfbI and putative proteins STM14_1138, STM14_3334, STM14_4825, and STM_5184) that has compelling potential to be exploited as vaccine development and/or drug target to curb the Salmonella infection.