Bacillus plakortidis sp. nov. and Bacillus murimartini sp. nov., novel alkalitolerant members of rRNA group 6

Abstract

The Gram-positive, alkali- and salt-tolerant marine bacterium strain P203T is described together with its closest phylogenetic neighbour, terrestrial isolate LMG 21005T. Strain P203T was isolated from material from the sponge Plakortis simplex that was obtained from the Sula-Ridge, Norwegian Sea. Strain LMG 21005T was an undescribed strain that was isolated from a church wall mural in Germany. Strains P203T and LMG 21005T were identified as novel alkalitolerant members of the Bacillus rRNA group 6 with a 16S rRNA gene sequence similarity of 99.5 %. The closest described neighbour, Bacillus gibsonii DSM 8722T, showed 99.0 % gene sequence similarity with P203T and 98.8 % similarity with strain LMG 21005T. Despite the high 16S rRNA gene sequence similarity, DNA–DNA cross-hybridization revealed only 25.8–34.1 % similarity amongst the three strains. The DNA G+C contents were 41.1 mol% for strain P203T and 39.6 mol% for strain LMG 21005T. Both strains grew well between pH 7 and pH 11. Strain P203T showed growth at moderate temperatures (from 4 to 30 °C) and in the presence of up to 12 % (w/v) NaCl at pH 9.7, whereas strain LMG 21005T was not salt tolerant (up to 4 % NaCl) and no growth was observed at 4 °C. The major fatty acids of strains P203T, LMG 21005T and the type strain of B. gibsonii were the saturated terminally methyl-branched compounds iso-C15 : 0 (19.8, 15.6 and 28.0 %, respectively) and anteiso-C15 : 0 (57.1, 48.6 and 45.2 %, respectively). Physiological and biochemical tests allowed genotypic and phenotypic differentiation of strains P203T and LMG 21005T from the six related Bacillus species with validly published names and supported the proposal of two novel species, Bacillus plakortidis [type strain P203T (=DSM 19153T=NCIMB 14288T)] and Bacillus murimartini [type strain LMG 21005T (=NCIMB 14102T)].