Effect of radioprotective agents in sporulation medium on Bacillus subtilis spore resistance to hydrogen peroxide, wet heat and germicidal and environmentally relevant UV radiation

Abstract

Aims: To determine the effects of cysteine, cystine, proline and thioproline as sporulation medium supplements on Bacillus subtilis spore resistance to hydrogen peroxide (H2O2), wet heat, and germicidal 254 nm and simulated environmental UV radiation. Methods and Results: Bacillus subtilis spores were prepared in a chemically defined liquid medium, with and without supplementation of cysteine, cystine, proline or thioproline. Spores produced with thioproline, cysteine or cystine were more resistant to environmentally relevant UV radiation at 280–400 and 320–400 nm, while proline supplementation had no effect. Spores prepared with cysteine, cystine or thioproline were also more resistant to H2O2 but not to wet heat or 254‐nm UV radiation. The increases in spore resistance attributed to the sporulation supplements were eliminated if spores were chemically decoated. Conclusions: Supplementation of sporulation medium with cysteine, cystine or thioproline increases spore resistance to solar UV radiation reaching the Earth’s surface and to H2O2. These effects were eliminated if the spores were decoated, indicating that alterations in coat proteins by different sporulation conditions can affect spore resistance to some agents. Significance and Impact of the Study: This study provides further evidence that the composition of the sporulation medium can have significant effects on B. subtilis spore resistance to UV radiation and H2O2. This knowledge provides further insight into factors influencing spore resistance and inactivation.

Effects of Electrolyzed Oxidizing Water on Inactivation of Bacillus subtilis and Bacillus cereus Spores in Suspension and on Carriers

“…In addition, even with the same strain and under the same experimental conditions, the results could vary depending on the medium and how the spores were prepared (Atrih and Foster ). It was reported that supplementation of sporulation medium with cysteine, cystine, or thioproline increased spore resistance to solar UV radiation and to H 2 O 2 if the spores were not decoated (Moeller and others ). B. subtilis spore could become more sensitive to H 2 O 2 when there was high Mn level and high Mn/Fe ration in the sporulation medium, but the resistance was unaffected to desiccation, wet or dry heat and ionizing radiation (Granger and others ).…”

“…Various spore inactivation chemicals and methods such as sodium hypochlorite, hydrogen peroxide, peracetic acid, wet heat, and UV radiation are commonly used to kill spores (Setlow and others ; Moeller and others ; Sudhaus and others ). However, unlike bacterial vegetative cells, spores of bacteria are difficult to inactivate because of its high resistance to various stresses.…”

Sporulation environment of emetic toxin-producingBacillus cereusstrains determines spore size, heat resistance and germination capacity

“…; Setlow ; Moeller et al . ), have been reported to influence sporulation and consequently spore properties. Interestingly, no apparent difference in DPA content of the spores, one of the factors influencing wet heat resistance (Setlow ), was observed between the five different sporulation conditions.…”

The cluster model of ultraviolet disinfection explains tailing kinetics

“…Significance and Impact of the Study: The ultraviolet dose-response behaviour of micro-organisms can now be explained in terms of parameters that have physical meaning and provide deep insight into the disinfection process.2016; Gerba and Betancourt 2017). Cluster formation of a sample can be influenced by inoculant concentration, sample deposition method, sample spreading method, buffer solution, test medium and temperature (Furness 1969;D'Argenio et al 2002;Moeller et al 2011;Cadnum et al 2016).Tailing is described as an upward concavity in survival curves, or sigmoid survival curves, that indicate increased resistance to inactivation (Withell 1942;Cerf 1977). Although many empirical mathematical models have been developed to fit survival curves with tails, no fundamentally-based model of microbial survival has yet been proposed that successfully explains the complete inactivation process.…”