Appl Environ Microbiol 1995 Oct;61(10):3633-3638 Here they looked at the effect mainly of core water content (by using mutants that had more core water in their spores I gather ) on heat and other tolerances. ---- Appl Environ Microbiol 1995 Oct;61(10):3633-3638 Spores of a Bacillus subtilis strain with an insertion mutation in peroxide. These data (i) suggest that core water content has little if any role in spore UV resistance and are consistent with binding of alpha/beta-type SASP to DNA being the major mechanism providing protection to spores from UV radiation; (ii) suggest that binding of alpha/beta-type SASP to DNA is the major mechanism unique to spores providing protection from dry heat; (iii) suggest that spore resistance to moist heat and hydrogen peroxide is affected to a large degree by the core water content, as increased core water resulted in large decreases in spore resistance to these agents; and (iv) indicate that since this decreased resistance (i.e., in dacB spores) is not associated with increased spore killing by DNA damage, spore DNA must normally be extremely well protected against such damage, presumably by the saturation of spore DNA by alpha/beta-type SASP. And according to another paper the main chemical giving Bacillus sp their resistance to heat and UV is : lipoteichoic acid. And here is some more: ---- Mikrobiologiia 1987 Nov;56(6):956-962 [Effect of initiated spores on the resistance of nongerminated resting forms of Bacillus cereus remaining in the suspension to the action of damaging agents]. The elevated resistance of a Bacillus cereus spore suspension against the action of UV was found to depend on the quantity of resting forms initiated in the suspension prior to an irradiation. The resistance against UV increased 80-50 times if 60-90% of spores were initiated in the suspension as compared to that of the original resting forms. When suspensions containing 40% of non-germinated B. cereus spores were kept at 4 degrees C for 14 days, the latter became 10 and 14 times more resistant to elevated temperature (90 degrees C) and chloramine (2.5%), respectively, as compared to control intact spores. The higher resistance of non-germinated spores against the action of physical and chemical damaging agents was registered within the entire period of experiments (over three months). This phenomenon was not observed if ca. 100% of spores were initiated in a suspension. The resistance of initiated spores against the action of UV was 40 times lower than that of B. cereus resting forms. This is all off the site: www.ncbi.nlm.nih.gov which gives abstacts and so on (and is I think much nicer to use than certain other famous biological abstract services) Keep well Garth Garth Cambray Camdini Apiaries Grahamstown Apis mellifera capensis Eastern Cape Prov. South Africa Time = Honey Standard Disclaimer applies to this post.