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International Journal of Microbiology
Volume 2011, Article ID 673136, 13 pages
Research Article

Bacillus Strains Most Closely Related to Bacillus nealsonii Are Not Effectively Circumscribed within the Taxonomic Species Definition

1USF Center for Biological Defense, College of Public Health, University of South Florida, 3602 Spectrum Boulevard, Tampa, FL 33612-9401, USA
2Department of Botany and Microbiology, University of Oklahoma, 770 Van Vleet Oval, Norman, OK 73019-6131, USA
3Harbor Branch Oceanographic Institute at Florida Atlantic University, 5600 US No. 1 North, Fort Pierce, FL 34946, USA

Received 10 May 2011; Revised 12 August 2011; Accepted 19 August 2011

Academic Editor: Luca Simone Cocolin

Copyright © 2011 K. Kealy Peak et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Bacillus strains with >99.7% 16S rRNA gene sequence similarity were characterized with DNA:DNA hybridization, cellular fatty acid (CFA) analysis, and testing of 100 phenotypic traits. When paired with the most closely related type strain, percent DNA:DNA similarities (% ) for six Bacillus strains were all far below the recommended 70% threshold value for species circumscription with Bacillus nealsonii. An apparent genomic group of four Bacillus strain pairings with 94%–70% was contradicted by the failure of the strains to cluster in CFA- and phenotype-based dendrograms as well as by their differentiation with 9–13 species level discriminators such as nitrate reduction, temperature range, and acid production from carbohydrates. The novel Bacillus strains were monophyletic and very closely related based on 16S rRNA gene sequence. Coherent genomic groups were not however supported by similarly organized phenotypic clusters. Therefore, the strains were not effectively circumscribed within the taxonomic species definition.