An increasing number of foodborne diseases are currently attributable to fresh vegetables and fruits contaminated with enteric pathogens such as Salmonella enterica spp. and Escherichia coli. Recent studies demonstrate that a variety of enteric pathogens are able to colonize onto plant surfaces and persist for a long time, which can subsequently lead to human infections. In order to understand the underlying mechanism of Salmonella adaptation to plants, I investigated the transcriptomics of Salmonella in contact with green vegetables cabbage and napa cabbage. Interestingly, Salmonella pathogenicity island (SPI)-1 genes, which are required for Salmonella invasion into host cells, were up-regulated upon contact with vegetables, suggesting that SPI-1 may be implicated in Salmonella colonization onto plant tissues as well as animal tissues. Furthermore, Salmonella transcriptomic profiling provided several genetic loci that showed significant changes in their expression in response to vegetables and were associated with bacterial adaptation to hostile niches, including nadA, fdnGHI, speF/potE, STM14_2269, ogt, and cbi operon. nadA was required for bacterial growth under nutrient-restricted conditions, while the others were required for bacterial invasion into host cells. The transcriptomes of Salmonella in contact with cabbage and napa cabbage provided insights into the comprehensive bacterial transcriptional response to plants and also suggested diverse virulence determinants relevant to Salmonella survival and adaptation.
