Purpose: The aim was to assess the biofilm formation of wild type and cellulose deficient Salmonella strains on the surface of whole tomatoes to characterize the role of cellulose biosynthesis in the interactions between Salmonella and the produce surface.
Methods: Analysis of the biofilm formation of S. Typhimurium and S. Typhimurium mutants deficient in thin aggregative fimbriae and/or cellulose production were completed on the tomato surface. Tomatoes were suspended in solutions of Salmonella strains diluted in sterile DI water for 24 hours at 30°C. After 24 hours, the tomato surfaces were stained with crystal violet. The tomatoes were then rinsed with DI water and acetic acid was used to solubilize the crystal violet staining. Biofilm formation was assessed through absorbance readings of the solutions at 595 nm.
Results: The deletion of the cellulose biosynthesis gene, bcsA, does significantly reduce the biofilm formation of S. Typhimurium on the tomato surface. The recorded absorbance for biofilm produced by wild type Salmonella on green, immature tomatoes was 0.682 ± 0.18 and 0.627 ± 0.16 on red, mature tomatoes. Absorbance readings for biofilm of Salmonella deficient in thin aggregative fimbriae and/or cellulose production ranged from 0.156 ± 0.04 to 0.17 ± 0.08 on immature tomatoes and 0.179 ± 0.13 to 0.188 ± 0.04 on mature tomatoes.
Significance: The results support that cellulose production is important in the biofilm formation and environmental persistence of S. Typhimurium on the tomato surface. Understanding the components important in the persistence of Salmonella can provide targets for preharvest treatments to reduce Salmonella on produce.