Analysis of cellular fatty acid methyl esters (FAMEs) for the identification of Bacillus anthracis

ABSTRACT

Bacillus anthracis, the etiological agent of anthrax has been classified into the Bacillus subgroup I with B. cereus, B. mycoides and B. thuringiensis based on morphological and DNA similarity. DNA studies have further indicated that these species have very AT-rich genomes and high homology, indeed it has been proposed that these four sub-species be recognized as members of the one species. Several methods have been developed to obtain good differentiation between these species. However, none of these methods provides the means for an absolutely correct differntiation. The analysis of fatty acid methyl esters (FAMEs) was employed as a quick, simple and reliable method for the identification of 21 B. anthracis strains and closley related strains. The most significant differences were found between B. anthracis and B. anthracis closely related strains in FAMEs profiles. All tested strains of B. anthracis had a branched fatty acid C17:1 Anteiso A, whereas the fraction of unsaturated fatty acid Iso C17:1 w10c was found in B. anthracis closely related strains. By UPGMA clustering analysis of FAMEs profiles, all of the tested strains were classified into two clusters defined at Euclidian distance value of 24.5. The tested strains of B. anthracis were clustered together including Bacillus sp. Kyungjoo 3. However, the isolates of B. anthracis closely related spp. Rho, S10A, 11R1, CAU9910, CAU9911, CAU9912 and CAU9913 were clustered with the other group. On the basis of these results, isolates of B. anthracis Bongchon, Kyungjoo 1, 2 and Bacillus sp. Kyungjoo 3 were reclassified as a B. anthracis. It is concluded that FAMEs analysis provides a sensitive and reliable method for the identification of B. anthracis from closely related taxa.