In vitro vs In vivo (Systemic)

Genetic mechanisms of Salmonella enterica serotype Typhimurium for overcoming host stressors
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 biochemical 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 (≥ 186, 000 unique insertions) was subjected to selection during growth in the presence of short chain fatty acid (100 mM Propionate), osmotic stress (3% NaCl) or oxidative stress (1mM H2O2) or survival in extreme acidic pH (30 min in pH 3) 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 the five stresses. Intriguingly, Salmonella pathogenicity island (SPI) genes like SPI-1, SPI-2, SPI-3, SPI-5, SPI-6 and SPI-11 are not only required during host infection, but also for fitness under in vitro conditions. 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.