Paenibacillus darwinianus sp. nov., isolated from gamma-irradiated Antarctic soil

A novel bacterium, strain Br(T), was isolated from gamma-irradiated soils of the Britannia drift, Lake Wellman Region, Antarctica. This isolate was rod-shaped, endospore forming, Gram-stain-variable, catalase-positive, oxidase-negative and strictly aerobic. Cells possessed a monotrichous flagellum. Optimal growth was observed at 18 °C, pH 7.0 in PYGV or R2A broth. The major cellular fatty acid was anteiso-C15 : 0 (63.4 %). Primary identified lipids included phosphatidylethanolamine, diphosphatidylglycerol and phosphatidylglycerol. Total phospholipid was 60 % (w/w) of the total lipid extract. MK-7 was the dominant isoprenoid quinone. The genomic DNA G+C content was 55.6 mol%. Based on 16S rRNA gene sequence similarity, strain Br(T) clusters within the genus Paenibacillus with similarity values ranging from 93.9 to 95.1 %. Phylogenetic analyses by maximum-likelihood, maximum-parsimony and neighbour-joining methods revealed that strain Br(T) clusters with Paenibacillus daejeonensis (AF290916), Paenibacillus tarimensis (EF125184) and Paenibacillus pinihumi (GQ423057), albeit with weak bootstrap support. On the basis of phenotypic, chemotaxonomic and phylogenetic characteristics, we propose that strain Br(T) represents a novel species, Paenibacillus darwinianus sp. nov. The type strain is Br(T) ( = DSM 27245(T) = ICMP 19912(T)).