Isolates of thermophilic bacteria obtained from an Austrian beet sugar factory were screened by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and freeze-fracture electron microscopy for the presence of glycosylated crystalline cell surface layers (S-layers). On the basis of similarities in the protein band patterns on SDS-PAGE gels and the lattice geometry of the S-layers as revealed by electron micrographs, the 31 isolates which we studied were clustered into five groups (groups I to V) and several strains which exhibited no common characteristics (group 0). We found that the organisms belonging to groups I to III had glycosylated S-layer proteins, but the highest carbohydrate contents were observed in group III organisms. Partial sequencing of the 16S ribosomal DNAs of selected representative strains of each group revealed that the group I, II, IV, and V isolates and the few group 0 strains were different from the group III strains. The results of DNA-DNA hybridization experiments, SDS-PAGE, and an analysis of polar lipids demonstrated that group III isolates L419-91, L420-91 (T = type strain), and L438-91 belong to the same species. We chose the group III organism sp. strain L420-91 for further analysis because of the high carbohydrate content of its S-layer protein. The taxonomic position of this isolate was determined by using a polyphasic approach. Phenotypic, chemotaxonomic, and genomic analyses revealed that strains L420-91, L419-91, and L438-91 represent a new species. We observed high levels of similarity between these strains and ATCC 12990, which also had a glycosylated S-layer protein. Our results show that strains L420-91, L419-91, and L438-91 and ATCC 12990 belong to the same species and that this species is a new species, which we name . The type strain of this species is strain L420-91 (= DSM 10154).


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