Genes ycfR, sirA and yigG contribute to the surface attachment of Salmonella enterica Typhimurium and Saintpaul to fresh produce

PLoS One. 2013;8(2):e57272. doi: 10.1371/journal.pone.0057272. Epub 2013 Feb 22.

Abstract

Salmonella enterica is a frequent contaminant of minimally-processed fresh produce linked to major foodborne disease outbreaks. The molecular mechanisms underlying the association of this enteric pathogen with fresh produce remain largely unexplored. In our recent study, we showed that the expression of a putative stress regulatory gene, ycfR, was significantly induced in S. enterica upon exposure to chlorine treatment, a common industrial practice for washing and decontaminating fresh produce during minimal processing. Two additional genes, sirA involved in S. enterica biofilm formation and yigG of unknown function, were also found to be differentially regulated under chlorine stress. To further characterize the roles of ycfR, sirA, and yigG in S. enterica attachment and survival on fresh produce, we constructed in-frame deletions of all three genes in two different S. enterica serovars, Typhimurium and Saintpaul, which have been implicated in previous disease outbreaks linked to fresh produce. Bacterial attachment to glass and polystyrene microtiter plates, cell aggregation and hydrophobicity, chlorine resistance, and surface attachment to intact spinach leaf and grape tomato were compared among wild-type strains, single-gene deletion mutants, and their respective complementation mutants. The results showed that deletions of ycfR, sirA, and yigG reduced bacterial attachment to glass and polystyrene as well as fresh produce surface with or without chlorine treatment in both Typhimurium and Saintpaul. Deletion of ycfR in Typhimurium significantly reduced bacterial chlorine resistance and the attachment to the plant surfaces after chlorinated water washes. Deletions of ycfR in Typhimurium and yigG in Saintpaul resulted in significant increase in cell aggregation. Our findings suggest that ycfR, sirA, and yigG collectively contribute to S. enterica surface attachment and survival during post-harvest minimal processing of fresh produce.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Bacterial Adhesion*
  • Biofilms
  • Fruit / microbiology*
  • Genes, Bacterial*
  • Hydrophobic and Hydrophilic Interactions
  • Phylogeny
  • Salmonella enterica / classification
  • Salmonella enterica / genetics*
  • Salmonella typhimurium / classification
  • Salmonella typhimurium / genetics*
  • Vegetables / microbiology*

Grants and funding

This work was supported by the United States Department of Agriculture National Institute of Food and Agriculture Grant no. 2011-67017-30016 under the Agriculture and Food Research Initiative Foundational Program Priority Area of Foodborne Pathogen-Plant Interactions (Program Area Code - A1301). The funder had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.