Heat resistant spores and prion diseases.

Robert Clark rgregoryclark at yahoo.com
Mon Apr 1 06:54:54 EST 2002

Thanks for the response. Actually the research works I cited were
given in terms of D-values. I copied the post below. It includes the
abstracts to the papers. The D-value for 125C, meaning the length of
time at this temperature to result in 10% viability, is 139 hours,
more than 5 and 1/2 days(!) Most bacterial spores such as Bacillus
subtilis could only survive for minutes at this temperature. As far as
I know this is the greatest dry heat survivability for any spore
known. However, as noted its moist heat survivability is much less
remarkable. This extreme dry heat resistance is what led to the
speculation by the researchers on the mechanism of its survival.
 I cited the D-value for 150C of 2.5 hours in the prior post to this
thread because I wanted to make a connection to the survivability of
the infectious agent in the Brown et.al. paper. which showed no
reduction in infectivity after dry heating for 5 and 15 minutes at
this temperature:

New studies on the heat resistance of hamster-adapted scrapie agent:
Threshold survival after ashing at 600°C suggests an inorganic
template of replication.
Proc. Natl. Acad. Sci. USA, Vol. 97, Issue 7, 3418-3421, March 28,

 I'm suggesting that a spore of this nature, and perhaps it needs only
to have this type of coat, would likely have very high survivability
at 150C for only minutes. The original discovers of this spore Bond
and Favero gave survivability curves for the various temperatures they
tested from which you could make estimates of its survival for only
minutes of dry heating.
 It is also interesting to note that spore based diseases such as that
due to anthrax typically have long incubation times, as does the TSE
type diseases. However, one notes the infectious agents in TSEs also
have extreme resistance to moist heating, which Bacillus
xerothermodurans does not have. Bond and Favero term it a mesophile.
It might be possible to transfer genes known to protective in
hyperthermophiles to B. xerothermodurans to give it moist heat
resistance as well.
 I looked up follow up research to that of Bond and Favero on B.
xerothermodurans in Science Citations Index and found very little had
been done on it since this work in the 70's. It would be interesting
to see its DNA makeup to see its relation to other types of bacteria,
perhaps infectious, and perhaps decipher the genes that allow it to
produce this type of spore coat.
 Its coat as I said has a type of honeycomed shape, like that of a
"buckyball", or fullerene:

Buckyballs Can Come from Outer Space
"A new study shows that carbon molecules known as fullerenes 
can originate outside the solar system and ride in on meteors."

 Take a look at the image of the buckyball on this Science News page
and compare it to the image of the B. xerothermodurans spore in the
papers I cited. The difference might be only one of scale. The image
makes it a little easier to explain my suggested mechanism for the
spores heat resistance. If you imagine the interior of the spore lying
within the fullerene then its contact with other spores will only be
along the thin edges of the fullerene cage. If it is also within a
granular soil then because of the spores small size most of the soil
grains will not be small enough to fit inside the faces of the
fullerene so the soil grains also would not contact the interior of
the spore. Then again conductive heating would only be communicated to
the spore along the thin edges of the fullerene. I'm suggesting this
would be rather analogous to the situation with for example space
shuttle thermal tiles where the tiles can be red hot in their interior
yet can be held on their edges. The situation with B. xerothermodurans
would be somewhat the reverse of this where the edges could be hot and
the interior stay relatively cool.
 To test this idea you could see how it's heat resistance holds up in
material with very small grains and also under high pressure. You
could also test its heat resistance under microwave oven heating.
 It is also interesting to note in regards to the extreme radiation
resistance of TSE infectious agents that spores with this type of coat
have also been suggested to be resistant to radiation. This is
discussed by Barry DiGregorio in his book _Mars: the Living Planet_:

"The most interesting discovery would not be made until Vishniac and 
Mainzer left with their Antarctica soil samples in stow and brought 
them to New Zealand, where they met with a microbiologist who was an 
expert in electron microscopy, Dr. John Waid of the Department of 
Botany at the University of Canterbury in Christchurch, New Zealand.
"Dr. Waid, while applying the high magnification abilities of the 
elctron microscope, observed a curious capsule surrounding many of 
the Antarcticaa microorganisms cells. He described it as "reminiscent 
of a honeycomb or sponge." Bacteria with such a protective capsule 
surrounding their cells would enjoy protection from the ultraviolet 
spectrum of the Sun's rays. In Antarctica, the untraviolet ray 
intensity is several orders of magnitude higher than in temperate 
latitudes, where rays are intercepted by the ozone layer."
_Mars: the Living Planet_, by Barry DiGregorio, p. 120. 

 Unfortunately, just as for B. xerothermodurans there does not seem to
have been much follow up research on these types of microbes. As
DiGregorio describes it, after their discover Wolf Vishniac died in
1973 there was no interest on the part of the scientific journals in
publishing his research on these radiation resistant microbes.
 Further on the likely radiation resistance of B. xerothermodurans can
be found in this post to sci.astro:

From: Robert Clark (rgregoryclark at yahoo.com)
Subject: Suggestion for a space ready spore and the origins of
radiation resistance.
Newsgroups: sci.astro, sci.physics, sci.bio.misc, sci.astro.seti
Date: 2002-01-15 09:15:03 PST

      Bob Clark

Note: this discussion originated under the thread title:

How animals in the hydrothermal vent can live with the high

From: Robert Clark (rgclark at my-deja.com)
Subject: Space ready spores? 
Newsgroups: sci.astro, sci.physics, sci.bio.misc, sci.astro.seti
Date: 2001-12-13 14:13:06 PST 
Recent discussions on the online BBS 

Inner Solar System Discussion Group (ISSDG)

concerned the possibility of spores surviving long periods in space to
travel from one planetary system to another. I was reminded of a type
of spore shown to be extremely resistant to dry heating:

The Antaeus Report: Orbiting Quarantine Facility - Scientific and 
Technical Information Branch, NASA, Washington D.C. 1981. 
NASA SP-454.
"One way to return a sample that is free of organisms
that could contaminate the Earth's biosphere is to
sterilize the sample during its return from Mars. The
sterilization treatment employed must be severe
enough to ensure that no life forms, as we know them,
could survive. Recently, terrestrial soil-inhabiting
microbes have been discovered that show a mere
10-fold reduction in viable organisms after 139 hours
at 125° C—a heating treatment 70 times longer than is
required to kill most soil organisms (ref. 15)."
Chapter 2, p. 9.

Two articles on it by Bond et. al. appeared in Applied 

Bacillus sp. ATCC 27380: a Spore with Extreme Resistance to 
Dry Heat
Bond, Favero, and Korber
Applied Microbiology, vol. 26, no. 4, Oct. 1973, p. 614-616
An unusual mesophilic Bacillus sp. was isolated from heated 
soil, and a cleaned spore preparation showed extraordinary 
resistance to dry heat (D_125C = 139H) and relative sensitivity to 
moist heat (D_80C = 61 min). Biochemical tests and 
morphology fit no described species.

Thermal Profile of a Bacillus Species (ATCC 27380) Extremely 
Resistant to Dry Heat.
Bond and Favero
Applied Microbiology, vol. 29, no. 6, June 1975, p. 859-860
Spores of Bacillus sp. ATCC 27380 were exposed at intervals to 
dry-heat temperatures ranging from 125 to 150 C. D-values from 
139 to 2.5 hours were obtained.

An article on it by Youvan et. al. also appeared in Life Sciences 
and Space Research:

Morphology of Extremely Heat Resistant Spores from Bacillus 
sp. ATCC 27380 by Scanning and Transmission Electron 
Youvan, Watanabe, Holmquist
Life Sciences and Space Research, vol. 15, 1976, p. 65-72.
Bacillus sp. ATCC 27380 is a recently discovered aerobic 
mesophile, isolated from surface soil, that produces spores with 
extreme resistance to dry heat: the length of time to 90% kill is 
139 hr. at 125 C and 13-17 hr. at 138 C. Values for spores from 
other known species range from 5 to 100 min. The molecular 
basis for this extreme heat resistance is unknown. We report a 
structural analysis of the internal and external mature spore 
morphology obtained by both scanning and transmission 
electron microscopy. Both modes of microscopy delineate a 
morel-like structure characterized by irregular, but distinct, 
polygonal ridges suggestive of extreme dehydration. Some 
spores also possess an appendage resembling the bun of a 
brioche. This bun-like body is possibly unique to this species. In 
cross-section the spore exhibits a many-layered structure, each 
layer with a characteristic fine structure. These morphological 
characters do not suffice to explain the observed resistance to 
dry heat at extreme temperatures. They do form a basis for the 
chemical characterization which will be necessary to understand 
this heat resistance at the molecular level. The concept of a 
"solid state spore" is put forward as a generalization that may be 
useful towards understanding this resistance.

The Bacillus is available from the American Type Culture 
Collection catalog:

ATCC Number: 27380 
Organism: Bacillus xerothermodurans Bond and Favero 

This page on the ATCC site also gives this reference on the 

Bacillus xerothermodurans sp. nov., a Species Forming 
Endospores Extremely Resistant to Dry Heat.
Bond and Favero
International Journal of Systematic Bacteriology, vol. 27, no. 2, 
April 1977, p. 157-169
An unusual mesophilic bacillus was isolated from soil, and a 
cleaned spore preparation of this organism showed extreme 
resistance to dry heat (D_125C = 139 hours, D_130C = 54 h, 
D_135C = 24 h, D_145C = 8 h, D_150C = 2.5 h; where D = time 
at temperature effecting 90% reduction in viable count); and 
relative sensitivity to moist heat (D_80C = 61 min). The 
biochemical tests, exterior and interior spore morphology, and 
growth characteristics of this organism do not fit those of any of 
the presently described species of bacteria. Consequently, we 
regard this organism as belonging to a new species, for which 
we propose the name Bacillus xerothermodurans. The type 
strain of this species has been deposited in the American Type 
Culture Collection as ATCC 27380.

 I put electron micrograph images of the spore in the BBS's Files 
section under the name "ATCC 27380.bmp". You need to be member of the
group to view the files.

Because it has an exceptional strong spore coat I thought it 
might also be highly resistant to radiation. In fact the spores' coat 
has a very interesting morphology. It has a type of honeycomb 
shape. It occurs to me however that it also looks like a "buckyball", 
i.e., buckminsterfullerene:

Buckyballs Can Come from Outer Space
"A new study shows that carbon molecules known as fullerenes 
can originate outside the solar system and ride in on meteors."

This article notes that buckyballs can be made in the lab and by 
lightning strikes on rocks. However, perhaps these buckyballs 
observed in carbonaceous meteorites could also be the spore 
coats of decayed microbes.

 Because of their very strong coats it may be that these spores could
survive the impact to the collectors of the Genesis and Stardust
missions. It is assumed that any complex organics would be dissociated
into simple compounds on impact to the collectors.

               Bob Clark

From: Robert Clark (rgclark at my-deja.com)
Subject: Will the Genesis mission confirm the theory of panspermia? 
Newsgroups: sci.astro, sci.space.policy, sci.physics, sci.astro.seti
Date: 2001-12-12 12:45:00 PST 

The Genesis mission's purpose is to collect samples of the solar 

Genesis Mission

Ironically this "Genesis" mission may provide evidence for the 
origins of life on Earth.

Svante Arrhenius first proposed the idea that bacteria could have 
been spread to Earth and between solar systems by radiation pressure:


This idea was criticized on the grounds that the exposure to 
radiation would kill such unprotected organisms. Hoyle and 
Wickramasinghe champion the idea that the microbes could be protected 
within comets that get ejected from one solar system and arrive at 
another on the time scale of 100's of millions of years.

However, if the microbes are propelled by the heavier charged 
particles of the solar wind then because of the microbes small mass 
they may quickly attain the speeds of the particles of the solar 
wind, on the order of millions of kilometers per hour. Then the time 
scale for them to reach the nearest solar systems, or to come here 
from them, would be on the order of only hundreds to thousands of 
If microbes are shed with material of a comet's tail, they would be 
spread in all directions by the solar wind, since comets appear in 
all directions both in and out of the ecliptic. This means the 
microbes would be much more likely to encounter another solar system.
Note also that due to the high speeds imparted to the microbes by 
the solar wind the amount of time they would spend within the 
originating solar system would be comparatively short, perhaps less 
than a year, thus reducing the damage they would suffer from 
How would the unprotected microbes survive this radiation? If the 
time they are in space is only on the order of hundreds of years then 
some bacterial spores may have this capability:


Also research shows that some bacteria species have the ability to 
repair damage to their DNA from even extreme doses of radiation. The 
most famous example of this is Deinococcus Radiodurans:

Meet Conan the Bacterium
Humble microbe could become
"The Accidental (Space) Tourist"

Recent research shows related high-radiation resistant microbes 
survive at below zero temperatures at the south pole:

Life in extreme conditions
"To their surprise, biochemical tests and electron microscope images 
show that the organisms can grow and divide even at -17 degrees C-the 
coldest condition the team tested. "Probably they could live at even 
lower temperatures," says Carpenter."

The question: will the Genesis mission collect such microbes while 
it is collecting samples of the solar wind?

Bob Clark

enigl at aol.com (Davin C. Enigl) wrote in message news:<3ca76e95.22608588 at news.earthlink.net>...
> On 31 Mar 2002 11:40:54 -0800, rgregoryclark at yahoo.com (Robert Clark)
> wrote:
> >  This spore retains 10% viability even after heating for 2.5 hours at
> >150 C. 
> So, that would be a 150 minute D-value at 150C.  It would be even more
> interesting to know the z-value because then you could predict the
> survival time at 600C and 1000C, there *will* be some sort of time
> value, you might need 10^9 to measure it however.
> >Then much higher survival would be expected at only 5 to 15
> >minutes.
> Well, sure witha D-value of 150, this is a merely a first order
> reaction.  Of course there is an initial non-linear bump, explained by
> A. Douglas King's work at the USDA.
> >Given the much higher survivability of this spore than other
> >bacteria it would be expected some fraction could survive exposure 370
> >C for several minutes.
> Sure, that merely depends on initial counts.  That is my initial
> point, the D-value is more important than the temperature.
> > In the refs. I cited in the post there was still an unresolved
> >question of how the spores were able to survive these high
> >temperatures.
> I guess they have not heard of D-value -- it is only about 120 years
> old (Hunt Brothers meat canning validation used to convince the US
> government safe commercial canning could take place. I was a senior
> microbiologist at Hunt's).   
> >One possibility could be the unusual honeycombed coat
> >possessed by the spore.
> The standard explanation is just that we have a thermodynamic
> first-order reaction.  The interesting thing is the growth curve:  
> 1) Lag, 
> 2) log-growth, 
> 3) stationary, then 
> 4) log-death phase.  
> Bacteria live and die logarithmically.  In fact, the log death happens
> with thing other than heat.  Cosmetic (chemical) preservatives also
> kill with a characteristically linear logarithmic decline.  There are
> some rather interesting causes for exceptions to this, however.
> >If the interior of the spore is encased in
> >this coat shaped somewhat like a buckyball then heat might be
> >communicated to the interior only through the thin sides of the coat,
> Interesting, but there is no experimental data supporting this as far
> as I know.  When we did spore clumping  experiments and looked at SEMs
> of the spore coat destruction, there was no significant effect on the
> D-values from this factor.  The IR radiation seemed to penetrate
> straight through even the biggest clumps we tested.  The inner cells
> did not have a lower probability to die over the ones on the outside
> of the clump, as far as we could tell.  This may not have been good
> enough method to tell, however.  
> >thus limiting the amount of heat communicated to the interior.
> > I'm thinking here of the case for example of space shuttle tiles that
> >can be held at the edges while white hot at the interior.
> Ok, that is dry.  We tested most things wet, that is a big difference
> -- deep sea vents are presumably wet in this ng thread.  Dry heat
> always takes longer.  And, we had this discussion a few months ago on
> heating anthrax spores with microwaves -- heat-loss calculations are
> needed.  It is amazing how much energy is needed to heat something up
> when it is "dry" and not touching anything else.
> -----------------

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