With repect to isolation you might want to look at the paper by Travers
et al. (Appl. Environ. Microbiol. 1987. 53:1263-1266. This method
supposedly allows isolation of Bt in the presence of other soil bugs.
I've tried it without much luck but others do use it. The companies that
are making (like Ecogen and Abbott) have very large Bt collections (like
5000-10,000 isolates) so isolation must not be super difficult. If you
want more information about the Travers paper, Phyllis Martin (second
author) is still at USDA in Beltsville and you could call her for
advice. With respect to DNA repair I can't tell you much. The bacteria
are present in soil in the spore form (delivered that way in the
products and liberated that way from dead insects) and so DNA repair is
not something going on much. The DNA is presumably protected from UV by
the Small Acid Soluble Proteins (SASPS) as described by Setlows lab. at
U. Conn Med. Center although I don't know of any SASP studies
specifically on Bt. Whether the toxin forming strains (Bt) are more
susceptible than the nontoxin formers (B. cereus) is unclear. Al
-------------- next part --------------
From: natasa at yorku.ca (Natasa Pasic-Knezevic)
Reply-To: ivan.pasic at utoronto.ca or natasa at yorku.ca
Newsgroups: bionet.microbiology
Subject: Re: Bacillus thuringiensis
Date: Tue, 05 Mar 1996 03:23:26 GMT
Organization: York University, Ontario, Canada
Message-ID: <4hgcgq$ia1 at sunburst.ccs.yorku.ca>
References: <4haupo$ovp at sunburst.ccs.yorku.ca> <4hf042$i59 at solaris.cc.vt.edu>
Al <Yousten at vt.edu> wrote:
>We need a bit more information i..e. are you asking about viability of
>the spores or about the effectiveness of the toxins (in the parasporal
>body). And are you concerned about residual effectiveness on plant
>leaves or in the water (Bti against mosquitoes)? Of course, the
>companies that have been producing Bt for the past 40 years or so have
>been interested in these questions and have attempted to prolong
>effectiveness. There are a number of papers, particularly in the older
>literature, concerning things like UV inactivation of toxins but I don't
>know of any phys/chem studies of the effects on the proteins
>themselves. The answer to your question may depend on the depth to which
>you are pursuing the question.
O.K. I'll explain what I mean.
I have read in a few papers that B. thuringiensis is extremely
sensitive to environmental conditions. Although it is a soil
bacterium, it is quite difficult to isolate it from the soil (does it
mean that it is present only in a small quantity?). Couple of times I
failed to isolate it from soils that were supposed to support its
growth.
I am mostly interested in DNA repair in B. thuringiensis. Some DNA
repair mechanisms - SOS (or SOB if you want) are found to be inhibited
in toxin-producing subspecies. So, what I am interested in is whether
or not this sensitiveness to environmental conditions might be due to
failure of some DNA repair functions in B. thuringiensis.
Thanks for response.
Ivan
