Author
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MARTIN, PHYLLIS |
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Submitted to: Bacillus thuringiensis Biotechnology and Environmental Benefit
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 10/2/1995 Publication Date: N/A Citation: N/A Interpretive Summary: While industry has isolated thousands of Bacillus thuringiensis bacterial strains from the environment for control of pest insects, very little is known about the role of this organism in the environment. This work summarizes 11 years of research on the isolation of B. thuringiensis from environmental sources using methods that were developed in this lab for handling large numbers of environmental isolates. It compares B. thuringiensis isolated from different environments such as soil, plants, calf pen bedding and human hands. The types of B. thuringiensis from these environments were found to be the same but the frequency of the different types varied by where they were isolated from. Other scientists will find this information useful in isolation of new strains of B. thuringiensis with toxicity to additional pest insects. It is also another piece in the puzzle of the environmental role of B. thuringiensis and the toxins these bacteria produce. Technical Abstract: Over the past 11 years my laboratory has acquired over 16,000 new isolates of Bacillus thuringiensis. Most of these strains were recovered from soil by taking advantage of the selective inhibition of B. thuringiensis spore germination by acetate. We have also recovered B. thuringiensis from plant material and animals, as well as fresh snow and ground water. Much of the preliminary identification and characterization of our isolates was performed using physiological assays on drops (dots) of test agar. In this way, hundreds or thousands of isolates can be easily and rapidly characterized. We also used agar dots of sporulation media to store these isolates. Thus, all our strains are stored after only one transfer from the environment from which they were isolated. We recovered in excess of 90% of the strains stored in this manner after a maximum of 11 years. Among our isolates we have found strains highly toxic to nematodes, Lepidoptera, and house flies. We have also isolated strains that make crystals similar to toxic strains, but which are not toxic to any of our test organisms. We have used these isolates to study B. thuringiensis turnover in soil, the prevalence of B. thuringiensis in agricultural soil and on crop plants, the presence of B. thuringiensis in calf pen bedding, and the frequency of recovery of B. thuringiensis from the hands of humans. |
