Ozone Sensitivity and Catalase Activity in Pigmented and Non-Pigmented Strains of .

BACKGROUND

Ozone exposure rapidly leads to bacterial death, making ozone an effective disinfectant in food industry and health care arena. However, microbial defenses may moderate this effect and play a role in the effective use of oxidizing agents for disinfection. is an opportunistic pathogen, expressing genes differentially during infection of a human host. A better understanding of regulatory systems that control expression of 's virulence genes and defenses is therefore valuable.

OBJECTIVE

Here, we investigated the role of pigmentation and catalase in on survival to ozone exposure.

METHOD

Pigmented and non-pigmented strains of were cultured to exponential or stationary phase and exposed to 5 ppm of gaseous ozone for 2.5 - 10 minutes. Survival was calculated via plate counts. Catalase activity was measured photometrically and tolerance to hydrogen peroxide was assayed by disk-diffusion.

RESULTS

Exposure of to 5 ppm gaseous ozone kills > 90% of cells within 10 minutes in a time and concentration-dependent manner. Although pigmented (grown at 28°C) survived ozonation better than unpigmented (grown at 35°C), non-pigmented mutant strains of had similar ozone survival rates, catalase activity and HO tolerance as wild type strains. Rather, ozone survival and catalase activity were elevated in 6 hour cultures compared to 48 hour cultures.

CONCLUSION

Our studies did not bear out a role for prodigiosin in ozone survival. Rather, induction of oxidative stress responses during exponential growth increased both catalase activity and ozone survival in both pigmented and unpigmented .