Genomic factors contributing to the resilience of Salmonella enterica on ready-to-eat muskmelon

Salmonella outbreaks have repeatedly been associated with muskmelons. This fruit poses a food safety risk due to its growth on the soil surface and because it is eaten raw. To identify genes under selection in S. enterica growing in this food matrix, barcoded transposon mutant libraries in three serovars of Salmonella, Typhimurium, Enteritidis, and Newport, were screened for survival and growth on muskmelon. The role of selected genes was subsequently verified in competition assays. Genes whose disruption caused a fitness effect in all three serovars were enriched for functions related to RNA degradation and ribosome biogenesis. The polyribonucleotide nucleotidyltransferase gene, pnp, and the D-3-phosphoglycerate dehydrogenase gene, serA , conferred an advantage when growing in muskmelon but not in a nutrition-rich control environment. This study provides a rare insight into genome-wide adaptation mechanisms of multiple Salmonella serovars to growth on food matrices, exemplified by muskmelons.