Schumann, Peter

Abstract The recently isolated strain L21-Fru-ABT represents moderately halophilic, obligately anaerobic and saccharolytic bacteria that thrive in the suboxic transition zones of hypersaline microbial mats. Phylogenetic analyses based on 16S rRNA genes, RpoB proteins and gene content indicated that strain L21-Fru-ABT represents a novel species and genus affiliated with a distinct phylum-level lineage originally designated Verrucomicrobia subdivision 5. A survey of environmental 16S rRNA gene sequences revealed that members of this newly recognized phylum are wide-spread and ecologically important in various anoxic environments ranging from hypersaline sediments to wastewater and the intestine of animals. Characteristic phenotypic traits of the novel strain included the formation of extracellular polymeric substances, a Gram-negative cell wall containing peptidoglycan and the absence of odd-numbered cellular fatty acids. Unusual metabolic features deduced from analysis of the genome sequence were the production of sucrose as osmoprotectant, an atypical glycolytic pathway lacking pyruvate kinase and the synthesis of isoprenoids via mevalonate. On the basis of the analyses of phenotypic, genomic and environmental data, it is proposed that strain L21-Fru-ABT and related bacteria are specifically adapted to the utilization of sulfated glycopolymers produced in microbial mats or biofilms.

A polyphasic study was undertaken to clarify the taxonomic position of endospore-forming strains 433-D9, 433-E17 and 121-X1. BOX-PCR-generated fingerprints indicated that they may be members of a single species. 16S rRNA gene sequence similarity demonstrated that a representative of this group, 433-D9, is affiliated closely with Bacillus arvi DSM 16317T (100 %), Bacillus arenosi DSM 16319T (99.8 %) and Bacillus neidei NRRL BD-87T (97.1 %). Sequence similarities revealed Bacillus pycnus NRRL NRS-1691T and several Kurthia species as the next nearest relatives. DNA–DNA hybridization results showed that strain 433-D9 is a member of B. arvi. Detection of l-Lys–d-Asp-based peptidoglycan in strain 433-D9, B. arvi DSM 16317T and B. arenosi DSM 16319T was in agreement with their close relationship, but differentiated these strains from B. neidei NRRL BD-87T and B. pycnus NRRL NRS-1691T, for which l-Lys–d-Glu was reported. A similar quinone system was detected in strains 433-D9, 433-E17, 121-X1, B. arvi DSM 16317T, B. arenosi DSM 16319T and B. neidei NRRL BD-87T. This system, unusual for bacilli, consisted of the major compound menaquinone MK-8 (69–80 %) and moderate amounts of MK-7 (19–30 %). This observation was in contrast to the predominance of MK-7 of the closest relative B. pycnus NRRL NRS-1691T, as also reported for representatives of the closely related non-endospore-forming genus Kurthia. Strains 433-D9, B. arvi DSM 16317T and B. arenosi DSM 16319T exhibited homogeneous and discriminative polar lipid profiles and fatty acid profiles consisting of major acids i-C15 : 0 and ai-C15 : 0 and moderate amounts of i-C17 : 1 ω10c and i-C17 : 1 I/ai-C17 : 1 B that discriminated them from closely related strains such as B. neidei NRRL BD-87T. On the basis of clear-cut discriminative chemotaxonomic markers, we propose strains 433-D9, 433-E17 and 121-X1, B. arvi DSM 16317T, B. arenosi DSM 16319T and B. neidei NRRL BD-87T to be reclassified within a separate genus. For this new taxon, we propose the name Viridibacillus gen. nov., and we propose the reclassification of Bacillus arvi, Bacillus arenosi and Bacillus neidei as Viridibacillus arvi gen. nov., comb. nov. (the type species of Viridibacillus, with the type strain DSM 16317T =LMG 22165T), Viridibacillus arenosi comb. nov. (type strain DSM 16319T =LMG 22166T) and Viridibacillus neidei comb. nov. (type strain NRRL BD-87T =DSM 15031T =JCM 11077T).

ABSTRACT A novel bacterial strain that was isolated from an Italian soil and was designated SOSP1-21 T forms branched mycelia in solid and liquid media and has a filamentous morphology similar to that of some genera belonging to the Actinobacteria . Electron microscopy showed that this organism has a grape-like appearance, resulting from interlacing of spores originating from sporophoric hyphae. Ten strains that are morphologically related to SOSP1-21 T were recovered from soil. Phylogenetic analyses of 16S rRNA gene segments confirmed the relatedness of these strains to SOSP1-21 T and indicated that the newly isolated strains form separate clades in a deeply branching lineage. The closest matches for the 16S rRNA sequences of all the strains (around 79% identity) were matches with representatives of the Chloroflexi , although the affiliation with this division was not supported by high bootstrap values. The strains are mesophilic aerobic heterotrophs and are also capable of growing under microaerophilic conditions. They all stain gram positive. Strain SOSP1-21 T contains ornithine, alanine, glutamic acid, serine, and glycine as the peptidoglycan amino acids. In addition, an unusual level of C16:1 2OH (30%) was found in the cellular fatty acids. The G+C content of SOSP1-21 T genomic DNA is 53.9%, and MK-9(H 2 ) was the only menaquinone detected. All these data suggest that SOSP1-21 T and the related strains may constitute a new division of filamentous, spore-forming, gram-positive bacteria. We propose the name Ktedobacter racemifer gen. nov., sp. nov. for strain SOSP1-21 T .