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

Salmonella outbreaks have repeatedly been associated with muskmelons. To identify genes under selection in S. enterica growing in this food matrix, barcoded transposon mutant libraries in three S. enterica serovars - Typhimurium, Enteritidis, and Newport - were screened for survival and growth on muskmelon. Applying stringent thresholds, a total of 26 genes in Typhimurium, 34 in Enteritidis, and 50 in Newport were found to significantly influence fitness during muskmelon interaction, with many of these being temperature dependent. Genes whose disruption affected fitness across all three serovars were enriched for functions related to RNA degradation and ribosome biogenesis. Targeted competition assays confirmed the contribution of selected genes, revealing nutrient-dependent phenotypes for most mutants. Remarkably, the polyribonucleotide nucleotidyltransferase gene, pnp, and the D-3-phosphoglycerate dehydrogenase gene, serA, conferred a selective advantage when growing in muskmelon but not under nutrition-rich control conditions. In contrast, the nitrogen regulation response regulator GlnG provided a muskmelon-specific fitness disadvantage. This study provides novel insights into genome-wide adaptation mechanisms of multiple Salmonella serovars to growth on muskmelons, revealing both shared and serovar-specific determinants while illustrating the dynamic genetic responses of S. enterica throughout the interaction period.