Reclassification of Geobacillus pallidus (Scholz et al. 1988) Banat et al. 2004 as Aeribacillus pallidus gen. nov., comb., nov.

Abstract

Although <i>Anoxybacillus</i> and <i>Geobacillus</i>, two genera of thermophilic bacteria close to the genus Bacillus, have only been described recently, the number of species in these genera has increased rapidly. Four thermophilic, lipolytic strains (DR01, DR02, DR03 and DR04) isolated from a hot spring in Veracruz (Mexico), which could not be identified phenotypically, were subjected to 16S rRNA gene sequence analysis. Three strains were identified as belonging to the genus <i>Anoxybacillus</i>, but strain DR03 was identified as <i>Geobacillus pallidus</i>. This result led us to perform a phylogenetic analysis of the genera <i>Anoxybacillus</i> and <i>Geobacillus</i> based on 16S rRNA gene sequences from all the type strains of these genera. Phylogenetic trees showed three major clusters, <i>Anoxybacillus</i>-<i>Geobacillus tepidamans</i>, <i>Geobacillus sensu stricto</i> and <i>Geobacillus pallidus</i>, while the 16S rRNA gene sequences of <i>G. pallidus</i> (DR03 and the type strain) showed low similarity to sequences of <i>Anoxybacillus</i> (92.5-95.1 %) and <i>Geobacillus</i> (92.8-94.5 %) species, as well as to <i>Bacillus subtilis</i> (92.2-92.4 %). In addition, <i>G. pallidus</i> could be differentiated from <i>Anoxybacillus</i> and <i>Geobacillus</i> on the basis of DNA G+C content and fatty acid and polar lipid profiles. From these results, it is proposed that <i>Geobacillus pallidus</i> should be classified in a novel genus, for which we propose the name <i>Aeribacillus</i>, as <i>Aeribacillus pallidus</i> gen. nov., comb. nov. The type strain of <i>Aeribacillus pallidus</i> is H12^T (=ATCC 51176^T =DSM 3670^T =LMG 19006^T).