The Small RNA DsrA Influences the Acid Tolerance Response and Virulence of Salmonella enterica Serovar Typhimurium

Abstract

The Gram-negative, enteropathogen Salmonella enterica serovar Typhimurium (S. Typhimurium) is exposed to various stress conditions during pathogenesis, of which acid stress serves as a major defense mechanism in the host. Such environments are encountered in the stomach and Salmonella containing vacuole of phagocytic and non-phagocytic cells. It is only recently that small RNAs (sRNAs) have come to the forefront as major regulators of stress response networks. Consequently, the sRNA DsrA which regulates acid resistance in Escherichia coli, has not been characterized in the acid tolerance response (ATR) of Salmonella. In this study, we show dsrA to be induced two and threefold under adaptation and challenge phases of the ATR, respectively. Additionally, an isogenic mutant lacking dsrA (ΔDsrA) displayed lower viability under the ATR along with reduced motility, feeble adhesion and defective invasion efficacy in vitro. Expression analysis revealed down regulation of several Salmonella pathogenicity island-1 (SPI-1) effectors in ΔDsrA compared to the wild-type, under SPI-1 inducing conditions. Additionally, our in vivo data revealed ΔDsrA to be unable to cause gut inflammation in C57BL/6 mice at 72 h post infection, although intracellular survival and systemic dissemination remained unaffected. A possible explanation may be the significantly reduced expression of flagellin structural genes fliC and fljB in ΔDsrA, which have been implicated as major proinflammatory determinants. This study serves to highlight the role of sRNAs such as DsrA in both acid tolerance and virulence of S. Typhimurium. Additionally the robust phenotype of non-invasiveness could be exploited in developing SPI-I attenuated S. Typhimurium strains without disrupting SPI-I genes.

Comparison of Acid Sanitizers on Salmonella Typhimurium Inoculated Commercial Poultry Processing Reuse Water

“…SBS is an inorganic acidifier with a pKa of 1.96 (Knueven, 1999). This low dissociation constant allows for highly acidic conditions, which Salmonella's acid tolerance mechanism and acid-shock proteins may not be able to compensate for, which would result in cell death (Foster and Hall, 1991;Knueven, 1999;Ryan et al, 2016). It has also been shown to be effective against Campylobacter when utilized preharvest (Line, 2002), and a 10% SBS spray decreased Salmonella counts by 2 logs on poultry carcasses (Li et al, 1997).…”

A ROD9 island encoded gene in Salmonella Enteritidis plays an important role in acid tolerance response and helps in systemic infection in mice

“…Bacterial cell propagation in MEM was done according to literature [17]. Briefly, it was obtained by culturing bacterial strains in triplicate over a period of 7 h at 37ºC, 180rpm.…”

“…Log-phase ATR assay was induced as mentioned in the literature [17]. Briefly, overnight grown WT, ΔSEN1008 and ΔSEN1008/pCH112-1008cultures in 5 ml MEM (37ºC, 180rpm) were sub-cultured (1:100 dilution) till an OD 600 of 0.4 were reached.…”

“…For the ATR assay, S. Enteritidis RNA was extracted from bacterial cultures growing at neutral pH (7.6), 1-h post-adaptation pH (4.4) and 1 hour postchallenge pH (3.1), followed by subsequent purification, cDNA synthesis and qRT-PCR analysis as already discussed. Guanylate monophosphate kinase (gmK) gene was used as housekeeping gene during ATR assay [17]. For fimbrial gene expression, ΔSEN1008 and WT were grown in Luria-Bertani (LB) broth, subcultured for 4 h (37°C, 120 rpm), whereas overnight grown cultures were used to checkin vitro SPI-2 genes and flagellar assembly genes expression and followed by usual RNA extraction, DNaseI purification, cDNA synthesis, and qRT-PCR study as mentioned.…”

Preliminary Transcriptome Analysis of Mature Biofilm and Planktonic Cells of Salmonella Enteritidis Exposure to Acid Stress

“…High-throughput deep sequencing, sequencing hundreds of thousands to millions of DNA molecules at one time, is one of the latest techniques used to investigate the global gene expression profiles of pathogenic bacteria in response to environmental stress (Karavolos et al, 2008 ; Deng et al, 2012 ; Amin et al, 2016 ; Beaubrun et al, 2017 ; Philips et al, 2017 ). A number of studies have evaluated the resistance of Salmonella planktonic cells to various stresses, in particular of Typhimurium serovar (Mühlig et al, 2014 ; Amin et al, 2016 ; Ryan et al, 2016 ), however, few study have focused on the transcriptome of biofilm formed by Enteritidis serovar exposed to acid stress due to the incomplete reference genome. Therefore, the goal of this study was to study the global gene expression profiles of mature biofilms formed by S .…”