Analysis of damage due to moist heat treatment of spores of<i>Bacillus subtilis</i>

Coleman, William H.; Setlow, Peter

doi:10.1111/j.1365-2672.2008.04127.x

Cited by 45 publications

(47 citation statements)

References 22 publications

(45 reference statements)

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“…An inverse relationship between core water content and wet-heat resistance has been well established for spores both within a species and across species and for spores of both Clostridium and Bacillus species (8). This correlation is thought to be causal as well, with lower core water contents presumably stabilizing core proteins more efficiently, and core protein damage seems most likely to be the reason for spore killing by wet heat (6,7). What is novel in our results was that superdormant spores had lower core water content and higher wet-heat resistance than the great majority of the original dormant spore population.…”

Section: Discussionmentioning

confidence: 36%

Superdormant Spores of Bacillus Species Have Elevated Wet-Heat Resistance and Temperature Requirements for Heat Activation

et al. 2009

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Purified superdormant spores of Bacillus cereus, B. megaterium, and B. subtilis isolated after optimal heat activation of dormant spores and subsequent germination with inosine, D-glucose, or L-valine, respectively, germinate very poorly with the original germinants used to remove dormant spores from spore populations, thus allowing isolation of the superdormant spores, and even with alternate germinants. However, these superdormant spores exhibited significant germination with the original or alternate germinants if the spores were heat activated at temperatures 8 to 15°C higher than the optimal temperatures for the original dormant spores, although the levels of superdormant spore germination were not as great as those of dormant spores. Use of mixtures of original and alternate germinants lowered the heat activation temperature optima for both dormant and superdormant spores. The superdormant spores had higher wet-heat resistance and lower core water content than the original dormant spore populations, and the environment of dipicolinic acid in the core of superdormant spores as determined by Raman spectroscopy of individual spores differed from that in dormant spores. These results provide new information about the germination, heat activation optima, and wet-heat resistance of superdormant spores and the heterogeneity in these properties between individual members of dormant spore populations.

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Section: Discussionmentioning

confidence: 36%

Superdormant Spores of Bacillus Species Have Elevated Wet-Heat Resistance and Temperature Requirements for Heat Activation

et al. 2009

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“…However, a possible reason for the early loss in spores' wet heat resistance during germination is that DPA is actually released during the heat treatment used to measure spore wet heat resistance. This release would generate a DPA-less spore that would then be rapidly killed at the temperatures used for assessing spore wet heat resistance (5,22).…”

Section: Resultsmentioning

confidence: 99%

“…However, if there is a major change in the spore's IM upon commitment, the IM of committed spores is perhaps much less able to retain its integrity at a high temperature that has a minimal effect on dormant spores. As a consequence, CaDPA is released from committed spores at this high temperature, and when this happens, the core water content rises and the committed and now DPA-less spores become heat sensitive and are rapidly killed (5,22). Indeed, oxidative damage to the dormant spore's IM makes this membrane much less able to retain CaDPA at an elevated temperature that has minimal effects on dormant spores and also increases the IM's permeability (23)(24)(25).…”

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confidence: 99%

Analysis of the Loss in Heat and Acid Resistance during Germination of Spores of Bacillus Species

Luu

Setlow

2014

J Bacteriol

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A major event in the nutrient germination of spores of Bacillus species is release of the spores' large depot of dipicolinic acid (DPA). This event is preceded by both commitment, in which spores continue through germination even if germinants are removed, and loss of spore heat resistance. The latter event is puzzling, since spore heat resistance is due largely to core water content, which does not change until DPA is released during germination. We now find that for spores of two Bacillus species, the early loss in heat resistance during germination is most likely due to release of committed spores' DPA at temperatures not lethal for dormant spores. Loss in spore acid resistance during germination also paralleled commitment and was also associated with the release of DPA from committed spores at acid concentrations not lethal for dormant spores. These observations plus previous findings that DPA release during germination is preceded by a significant release of spore core cations suggest that there is a significant change in spore inner membrane permeability at commitment. Presumably, this altered membrane cannot retain DPA during heat or acid treatments innocuous for dormant spores, resulting in DPA-less spores that are rapidly killed.

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“…This suggests that during wet-heat treatment some spores should retain CaDPA for a short period, even if they are already dead from protein damage, and some B. subtilis spores in populations treated with wet heat have been shown to do just that (7). Presumably wet heat causes damage to some crucial protein or proteins such that while CaDPA is retained, the spores are not viable, and even if they can germinate, they cannot progress into outgrowth (7,8). However, with further wet-heat treatment, more protein damage accumulates, including damage to proteins in the spore's inner membrane, and ultimately, this damaged membrane ruptures, leading to rapid CaDPA release.…”

Section: Vol 76 2010mentioning

confidence: 99%

Characterization of Wet-Heat Inactivation of Single Spores of Bacillus Species by Dual-Trap Raman Spectroscopy and Elastic Light Scattering

Zhang

Kong

Setlow

et al. 2010

Appl Environ Microbiol

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Dual-trap laser tweezers Raman spectroscopy (LTRS) and elastic light scattering (ELSBacterial spores of Bacillus species are formed in sporulation and are metabolically dormant and extremely resistant to a variety of harsh conditions, including heat, radiation, and many toxic chemicals (37). Since spores of these species are generally present in foodstuffs and cause food spoilage and food-borne disease (37, 38), there has long been interest in the mechanisms of both spore resistance and spore killing, especially for wet heat, the agent most commonly used to kill spores. The killing of dormant spores by wet heat generally requires temperatures about 40°C higher than those for the killing of growing cells of the same strain (37, 43). A number of factors influence spore wet-heat resistance, with a major factor being the spore core's water content, as spores with higher core water content are less wet-heat resistant than are spores with lower core water (15,25). The high level of pyridine-2,6-dicarboxylic acid (dipicolinic acid [DPA]) and the types of its associated divalent cations, predominantly Ca 2ϩ , that comprise ϳ25% of the dry weight of the core also contribute to spore wet-heat resistance, although how low core water content and CaDPA protect spores against wet heat is not known. The protection of spore DNA against depurination by its saturation with a group of ␣/␤-type small, acid-soluble spore proteins also contributes to spore wet-heat resistance (14,23,33,37).Despite knowledge of a number of factors important in spore wet-heat resistance, the mechanism for wet-heat killing of spores is not known. Wet heat does not kill spores by DNA damage or oxidative damage (35, 37). Instead, spore killing by this agent is associated with protein denaturation and enzyme inactivation (2, 7, 44), although specific proteins for which damage causes spore death have not been identified. Wet-heat treatment also often results in the release of the spore core's large depot of CaDPA. The mechanism for this CaDPA release is not known but is presumably associated with the rupture of the spore's inner membrane (7). In addition, the relationship between protein denaturation and CaDPA release is not clear, although recent work suggests that significant protein denaturation can occur prior to CaDPA release (7). Almost all information on spore killing by moist heat has been obtained with spore populations, and essentially nothing is known about the behavior of individual spores exposed to potentially lethal temperatures in water. Given the likely heterogeneity of spores in populations, in particular in their wetheat resistances (16,18,39,40), it could be most informative to analyze the behavior of individual spores exposed to high temperatures in water.Raman spectroscopy is widely used in biochemical studies, as this technique has high sensitivity and responds rapidly to subtle changes in molecule structure (1, 22, 31). In addition,

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Analysis of damage due to moist heat treatment of spores ofBacillus subtilis

Cited by 45 publications

References 22 publications

Superdormant Spores of Bacillus Species Have Elevated Wet-Heat Resistance and Temperature Requirements for Heat Activation

Superdormant Spores of Bacillus Species Have Elevated Wet-Heat Resistance and Temperature Requirements for Heat Activation

Analysis of the Loss in Heat and Acid Resistance during Germination of Spores of Bacillus Species

Characterization of Wet-Heat Inactivation of Single Spores of Bacillus Species by Dual-Trap Raman Spectroscopy and Elastic Light Scattering

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