Enterotoxin-Deficient Bacillus thuringiensis for Crop Safety
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Solution Overview
Problem
Current Bacillus thuringiensis strains used for biological control of insect pests pose safety concerns due to their production of enterotoxins associated with human food poisoning, as they are closely related to Bacillus cereus, which can produce toxins causing food-borne diseases, and existing attempts to eliminate these toxins have been unsuccessful.
Innovation Solution
Development of enterotoxin-deficient Bacillus thuringiensis strains by mutating the operons that encode NHE, HBL, HBLa1, and HBLa2 enterotoxins, making them non-functional, while retaining insecticidal activity, thereby reducing the risk of human toxicity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Bacillus thuringiensis strains are used for biological control of insect pests, then insecticidal efficacy is improved, but human safety deteriorates due to production of enterotoxins associated with food poisoning
Solution Approach 1:
The patent removes the harmful enterotoxin-producing operons (nhe, hbl, hbla1, hbla2) from the Bacillus thuringiensis genome while retaining the beneficial insecticidal cry genes. This extraction of the disturbing part (enterotoxin genes) resolves the contradiction by eliminating human health risks while preserving insect control capabilities
Solution Approach 2:
The patent segments the bacterial genome into functional modules: retaining the insecticidal cry operons while eliminating the harmful enterotoxin operons (nheABC, hblCD, hbla1, hbla2). This segmentation allows selective preservation of beneficial functions and removal of harmful ones, resolving the safety-efficacy contradiction
2Object-affected harmful factors
If enterotoxin genes are eliminated from Bacillus thuringiensis, then human safety is improved, but the strain may lose biological control functionality
Solution Approach 1:
The patent selectively extracts only the harmful enterotoxin operons (nhe, hbl, hbla1, hbla2) while leaving the essential insecticidal cry operons intact. This precise extraction ensures human safety improvement without compromising biological control functionality
Solution Approach 2:
The patent applies different quality modifications to different genomic regions: the enterotoxin operons are inactivated for safety, while the cry insecticidal operons are preserved for functionality. This local differentiation resolves the contradiction by applying opposite treatments to different functional modules
3Object-affected harmful factors
If multiple operons are mutated to create enterotoxin-deficient strains, then safety is improved, but device complexity increases
Solution Approach 1:
The patent combines multiple enterotoxin operons (nheABC, hblCD, hbla1, hbla2) into a unified deletion strategy. By treating these separate operons as a combined harmful module to be eliminated, the approach simplifies the overall process compared to addressing each operon independently, thus reducing complexity while achieving comprehensive safety
Data Source
AI summary
Some HBL and NHE enterotoxins are known to cause food-borne diseases in humans. Enterotoxin-deficient mutants of member strains of the Bacillus cereus group that do not produce HBL, HBLa1, HBLa2, or NHE enterotoxins are disclosed. Enterotoxin-deficient mutants are suitable for use as biocontrol agents. Methods for making the mutants and for using the mutants are described.