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Phylogenetic distribution of phenotypic traits in Bacillus thuringiensis determined by multilocus sequence analysis
Michael B Blackburn1, Phyllis A W Martin, Daniel Kuhar
1Invasive Insect Biocontrol and Behavior Laboratory, Agricultural Research Service, United States Department of Agriculture, Henry A. Wallace Beltsville Agricultural Research Center, Beltsville, Maryland, United States of America. mike.blackburn@ars.usda.gov
Plos One
|June 14, 2013
Summary
Diverse Bacillus thuringiensis isolates were classified using biochemical tests and multilocus sequence typing. Bacillus thuringiensis varieties israelensis and kurstaki were found to be the most abundant in soil samples.
Area of Science:
- Microbiology
- Molecular Biology
- Biochemistry
Background:
- Bacillus thuringiensis (Bt) is a soil bacterium with diverse strains used as biopesticides.
- Accurate classification of Bt strains is crucial for understanding their ecology and application.
- Phenotypic and genotypic characterization are key methods for bacterial classification.
Purpose of the Study:
- To classify diverse Bacillus thuringiensis isolates using phenotypic and phylogenetic analyses.
- To investigate the correlation between phenotypic traits and genetic diversity within Bt.
- To determine the most abundant Bt varieties in soil environments.
Main Methods:
- Phenotypic classification using six biochemical tests: amylase (T), lecithinase (L), urease (U), acid from sucrose (S), acid from salicin (A), and esculin hydrolysis (E).
- Phylogenetic analysis of 82 isolates representing 15 common phenotypic profiles using multilocus sequence typing (MLST).
- Comparison of phenotypic profiles with sequence types and known Bt varieties.
Main Results:
- 19 sequence types were identified among the isolates, with 8 being novel.
- Approximately 70% of isolates belonged to sequence types associated with varieties kurstaki, finitimus, morrisoni, and israelensis.
- Little correlation was observed between phenotypic traits and phylogenetic position, with significant phenotypic variation within sequence types.
- Specific phenotypic profiles (TLUAE, LSAE, TS) showed strong associations with particular sequence types and Bt varieties.
- Bacillus thuringiensis varieties israelensis and kurstaki were identified as the most prevalent in soil.
Conclusions:
- Multilocus sequence typing provides a robust phylogenetic framework for classifying Bacillus thuringiensis.
- Phenotypic variation within sequence types highlights the complexity of Bt strain diversity.
- Bacillus thuringiensis varieties israelensis and kurstaki are dominant in soil ecosystems, suggesting their ecological significance.
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