Toxins of Bacillus thuringiensis in Transgenic Organisms: Persistence and Ecological EffectsEPA Grant Number: R826107
Title: Toxins of Bacillus thuringiensis in Transgenic Organisms: Persistence and Ecological Effects
Investigators: Stotzky, Guenther
Institution: New York University
EPA Project Officer: Hahn, Intaek
Project Period: November 7, 1997 through November 6, 2000 (Extended to May 5, 2002)
Project Amount: $393,411
RFA: Exploratory Research - Environmental Biology (1997) RFA Text | Recipients Lists
Research Category: Ecosystems , Biology/Life Sciences
The release of transgenic plants and bacteria containing genes from subspecies of Bacillus thuringiensis (Bt) that code for insecticidal proteins poses a potential hazard to the environment. The continual production of the toxins, especially those encoded by truncated genes that express active toxins rather than inactive protoxins, by growing transgenic organisms that are indigenous or adapted to the specific habitat may exceed consumption by insect larvae and biotic and abiotic inactivation. Hence, the toxins could accumulate to concentrations that may constitute a hazard to nontarget organisms and that could result in the selection and enrichment of toxin-resistant target insects. The accumulation and persistence would be enhanced if the toxins are bound on particles (e.g., clays and humic substances) in the environment and, thereby, are rendered less accessible for microbial degradation.
The objectives of this project are to: 1) determine the persistence in soil of the toxins of subspecies of Bt (e.g., kurstaki, antilepidopteran; tenebrionis, anticoleopteran; israelensis, anti-dipteran, which will also be studied in aquatic systems); 2) elucidate the mechanisms responsible for persistence (e.g., does binding of the toxins on soil constituents affect the rate and extent of microbial degradation?); 3) compare the insecticidal activity of free and particle-bound toxins, as well as their toxicity to microorganisms; and 4) evaluate the effects of the toxins on microbial populations and processes in soil (e.g., metabolic activity, transformations of carbon and nitrogen, activity of "soil" enzymes, species diversity).
The methodology that will be used to attain these objectives includes: 1) equilibrium adsorption and binding studies with clays and humic substances; 2) insect bioassays; 3) enzyme-linked immunosorbent and flow cytometry assays for monitoring the toxins in soil; 4) respirometric, enzymatic, species diversity, and other assays of microbial populations and processes in soil; and 5) toxicological assays with microorganisms.
These studies have relevance to the mission of EPA to protect both the environment and human health by the application of sound science to "long-term research that anticipates future environmental problems" and their resolution "and strives to fulfill significant gaps in knowledge relevant to protecting the environment". The large-scale release of such transgenic plants and bacteria could: 1) negatively affect beneficial insects; 2) result in an increase in toxin-resistant harmful insects; 3) alter microbial populations and processes in soil that are essential for biogeo-chemical cycles; and 4) pose a hazard to other components of the biosphere. These studies will also provide additional basic information on the mechanisms involved in interactions between components of soil and natural (e.g., bioactive compounds produced by transgenic plants) and xenobiotic organic compounds and on the potential ecological effects of such interactions.