Arundinibacter roseus gen. nov., sp. nov., a new member of the family Cytophagaceae.

Three Gram-stain-negative, aerobic, non-motile, oxidase- and catalase positive, rod-shaped, pink-coloured bacterial strains, DMA-K-7aT, DMA-K-1 and DMG-N-1, were isolated from water sampled at Lake Ferto/Neusiedler See (Hungary). Phylogenetic analysis based on the 16S rRNA gene sequences revealed that the strains form a distinct linage within the family Cytophagaceae of the phylum Bacteroidetes, and their closest relatives are Rhabdobacter roseus R49T (95.66 %) and Dyadobacter sediminis Z12T (95.38 %). The assembled genome of strain DMA-K-7aT had a total length of 5.8 Mb and a DNA G+C content of 45.7 mol%. The major isoprenoid quinone was menaquinone-7 (MK-7). The major cellular fatty acids were C16 : 1 ω7c, iso-C15 : 0, C16 : 1 ω5c, C16 : 0 and iso-C17 : 0 3-OH. The polar lipid profile contained phosphatidylethanolamine, phosphatidylserine, an unknown aminolipid, an unknown glycolipid and five unknown lipids. Flexirubin-type pigments were absent. Strain DMA-K-7aT (=DSM 106737T=NCAIM B.02641T) is proposed as the type strain of a new genus and species in the family Cytophagaceae, for which the name Arundinibacter roseus gen. nov., sp. nov. is proposed.

Electron microscopic detection and activity of glucosyltransferase B, C, and D in the in situ formed pellicle.

OBJECTIVE: Glucosyltransferases (GTFs) represent a virulence factor of mutans streptococci. The aim of the present in situ study was to investigate the distribution of different GTF-isoforms in the pellicle. DESIGN: Bovine enamel slabs were fixed on buccal and palatal sites of individual splints worn by five subjects for 30 and 120 min to allow pellicle formation. Pellicle specimens were processed for transmission electron microscopy (TEM) and field emission in-lens scanning electron microscopy (FEI-SEM). Gold-immunolabelling was used for detection of GTF-isoforms B, C and D. Furthermore, glucosyltransferase activity of 3-, 30- and 120-min pellicles was tested via determination of fructose release. RESULTS: All isoforms of the enzyme were found to be randomly distributed within all layers of the pellicle. In cross-sections (TEM), GTF D was the most abundant isoform. More labelled molecules were detected on buccal sites compared with palatal surfaces, the number of molecules detected increased with time. The amount of GTF B, C and D found on the pellicle surface by FEI-SEM showed no correlation with pellicle formation time or localisation in the oral cavity. Overall, GTF D was detected more frequently on the surface than GTF B and C. All pellicles tested showed GTF-activity. CONCLUSION: The study shows for the first time the presence of the GTF-isoforms B, C and D within all layers of the in situ formed pellicle. This emphasises the impact of streptococcal products on the composition of the pellicle and illustrates a mechanism used by bacteria to colonize dental surfaces.