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Phylogeny of Bacillus sphaericus-like organisms
International Journal of Systematic and Evolutionary Microbiology
|October 18, 2000
Summary
Bacillus sphaericus is a genetically diverse group, not a single species. This bacterial heterogeneity explains why mosquito pathogenicity varies among strains, with pathogenic types forming a distinct cluster.
Area of Science:
- Microbiology
- Bacterial Taxonomy
- Molecular Phylogenetics
Background:
- The Bacillus sphaericus group includes four species, with mosquito pathogenicity noted in some B. sphaericus sensu lato strains.
- Genetic and phenotypic variability within B. sphaericus complicates understanding its characteristics, including pathogenicity.
Purpose of the Study:
- To investigate the genetic heterogeneity of Bacillus sphaericus using 16S rDNA sequencing.
- To compare phylogenetic data with phenotypic characteristics like fatty acid profiles.
Main Methods:
- Phylogenetic analysis of 16S rDNA sequences from 58 B. sphaericus strains.
- Comparison of sequence data with whole-cell fatty acid profiles and other phenotypic traits.
Main Results:
- 16S rDNA analysis revealed seven distinct clusters within B. sphaericus-like strains.
- Pathogenic strains formed a distinct cluster, closely related to, or part of, the Bacillus fusiformis group.
- Phenotypic groupings aligned with the 16S rDNA phylogenetic clusters, confirming significant heterogeneity.
Conclusions:
- Bacillus sphaericus is a genetically and phenotypically heterogeneous taxon comprising at least seven distinct taxa.
- Mosquito-pathogenic strains belong to a separate group, not B. sphaericus sensu stricto, explaining pathogenicity variability.
- The identified heterogeneity is key to understanding the variable mosquito pathogenicity observed in B. sphaericus strains.