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Updated: Jun 13, 2026
09:42
Isolation and Selection of Entomopathogenic Fungi from Soil Samples and Evaluation of Fungal Virulence against Insect Pests
Published on: September 28, 2021
Distribution of phenotypes among Bacillus thuringiensis strains
Phyllis A W Martin1, Dawn E Gundersen-Rindal, Michael B Blackburn
1USDA/ARS Invasive Insect Biocontrol and Behavior Laboratory, Beltsville, MD 20705, USA. Phyllis.martin@ars.usda.gov <Phyllis.martin@ars.usda.gov>
Systematic and Applied Microbiology
|May 8, 2010
Summary
Biochemical profiling of Bacillus thuringiensis isolates revealed six key traits for distinguishing strains. Specific combinations of these traits correlated with parasporal crystal types and insect toxicity, aiding in strain characterization.
Area of Science:
- Microbiology
- Biochemistry
- Insect Pathology
Background:
- Bacillus thuringiensis (Bt) is a ubiquitous soil bacterium known for its insecticidal properties.
- Phenotypic characterization is crucial for understanding microbial diversity and function.
- Standardized biochemical tests offer a reliable method for differentiating bacterial isolates.
Purpose of the Study:
- To phenotypically profile a global collection of Bacillus thuringiensis isolates using standard biochemical tests.
- To identify useful biochemical traits for distinguishing Bt strains.
- To investigate correlations between biochemical phenotypes and parasporal crystal characteristics, including insect toxicity.
Main Methods:
- Extensive collection of Bacillus thuringiensis isolates from diverse geographical locations.
- Standard biochemical profiling including urease production, esculin hydrolysis, acid production from salicin and sucrose, phospholipase C activity, and starch hydrolysis.
- Analysis of phenotypic trait combinations and their association with parasporal crystal morphology and insect toxicity.
Main Results:
- Six phenotypic traits (urease, esculin hydrolysis, salicin/sucrose acid production, phospholipase C, starch hydrolysis) were identified as useful for distinguishing Bt isolates.
- Fifteen phenotypic combinations accounted for approximately 80% of all isolates, with TL being the most common.
- Correlations were found between specific biochemical traits and parasporal crystal types, influencing insect toxicity (e.g., amorphous crystals with dipteran toxicity, bipyramidal crystals with lepidopteran toxicity).
Conclusions:
- Biochemical profiling provides a robust method for characterizing Bacillus thuringiensis strains.
- Specific biochemical phenotypes are linked to distinct parasporal crystal types and associated insecticidal activity.
- This characterization aids in understanding Bt diversity and optimizing its application as a biopesticide.
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