Effect of sporulation and recovery medium on the heat resistance and amount of injury of spores from spoilage bacilli

Abstract

Aims: To assess the in¯uence of sporulation media on heat resistance, and the use of stress recovery media to measure preservation injury of spores of ®ve representative spoilage bacilli. Methods and Results: Bacillus spores prepared on nutrient agar supplemented with Ca 2+ , Mg 2+ , Mn 2+ , Fe 2+ and K + were more heat-resistant than spores obtained from nutrient agar with Mn 2+ . This increased heat resistance correlated with a decrease in the protoplast water content as determined by buoyant density sedimentation. The degree of preservation injury severity could be assessed on media containing NaCl at moderate pH and organic acids at acid pH. Ca-DPA, K + or proline were added to the recovery media to demonstrate that heat probably caused injury to both spore germination and the outgrowth system. Signi®cance and Impact of the Study 2 : The metal content of sporulation media can strongly effect the validity of preservation resistance studies. The distinctive recovery media developed here can be relevant for assessing and comparing new preservation technologies.

Importance of Considering Injured Microorganisms in Sterilization Validation

“…According to the present author's experiment, Ca, vitamin mixtures, Lalanine, puruvate and glucose are appropriate agents to promote germination (Shintani, 2006). Mg ion does not successfully promote germination contrary to reported results (Cazemier et al, 2001;Busta et al, 1976). …”

MALDI-TOF-MS analysis of bacterial spores: Wet heat-treatment as a new releasing technique for biomarkers and the influence of different experimental parameters and microbiological handling

“…Sporulation was obtained on nutrient agar (Becton, Dickinson and Co., Cockeyville, MD) supplemented with a metal mix containing MgSO 4 , KCl, CaCl 2, MnSO 4 , and FeSO 4 as described by Cazemier et al [17]. 100 l of bacterial stock was spread on nutrient agar plates, which were then incubated at 37°C for five days.…”

How Moist Heat Kills Spores of Bacillus subtilis

“…Moist-heat-treated spores often appear injured, and although they can be recovered on rich medium plates, in contrast to unheated spores they are only poorly recovered on plates with high salt or with low nutrient levels (5,8,13). This suggests that some spore protein or proteins can be damaged by moist-heat treatment, although this damage may be only conditionally lethal.…”

“…This suggests that some spore protein or proteins can be damaged by moist-heat treatment, although this damage may be only conditionally lethal. Moistheat-killed spores often, but not always, have also lost DPA and may have a few core enzymes inactivated and/or denatured (5,15,37). However, it is not known if any or all of these events are the cause of spore killing or take place only after some other initial lethal event.…”