AUTHOR=Jayeola Victor , McClelland Michael , Porwollik Steffen , Chu Weiping , Farber Jeffrey , Kathariou Sophia 

TITLE=Identification of Novel Genes Mediating Survival of Salmonella on Low-Moisture Foods via Transposon Sequencing Analysis

JOURNAL=Frontiers in Microbiology

VOLUME=11

YEAR=2020

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2020.00726

DOI=10.3389/fmicb.2020.00726

ISSN=1664-302X

ABSTRACT=<p><italic>Salmonella enterica</italic> is the leading foodborne pathogen associated with outbreaks involving low-moisture foods (LMFs). However, the genes involved in <italic>Salmonella’</italic>s long-term survival on LMFs remain poorly characterized. In this study, in-shell pistachios were inoculated with Tn<italic>5-</italic>based mutant libraries of <italic>S</italic>. Enteritidis P125109, <italic>S</italic>. Typhimurium 14028s, and <italic>S</italic>. Newport C4.2 at approximate 10<sup>8</sup> CFU/g and stored at 25°C. Transposon sequencing analysis (Tn-seq) was then employed to determine the relative abundance of each Tn<italic>5</italic> insertion site immediately after inoculation (T<sub>0</sub>), after drying (T<sub>1</sub>), and at 120 days (T<sub>120</sub>). In <italic>S</italic>. Enteritidis, <italic>S</italic>. Typhimurium, and <italic>S</italic>. Newport mutant libraries, the relative abundance of 51, 80, and 101 Tn<italic>5</italic> insertion sites, respectively, was significantly lower at T<sub>1</sub> compared to T<sub>0</sub>, while in libraries of <italic>S</italic>. Enteritidis and <italic>S</italic>. Typhimurium the relative abundance of 42 and 68 Tn<italic>5</italic> insertion sites, respectively, was significantly lower at T<sub>120</sub> compared to T<sub>1</sub>. Tn<italic>5</italic> insertion sites with reduced relative abundance in this competition assay were localized in DNA repair, lipopolysaccharide biosynthesis and stringent response genes. Twelve genes among those under strong negative selection in the competition assay were selected for further study. Whole gene deletion mutants in ten of these genes, <italic>sspA</italic>, <italic>barA</italic>, <italic>uvrB</italic>, <italic>damX</italic>, <italic>rfbD</italic>, <italic>uvrY</italic>, <italic>lrhA</italic>, <italic>yifE, rbsR</italic>, and <italic>ompR</italic>, were impaired for individual survival on pistachios. The findings highlight the value of combined mutagenesis and sequencing to identify novel genes important for the survival of <italic>Salmonella</italic> in low-moisture foods.</p>