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.
 
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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:
 
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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
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