Tannerella serpentiformis sp. nov., isolated from the human mouth.

Three strains representing the previously uncultured human oral Tannerella taxon HMT-286 were recently isolated from the subgingival plaque of a patient with chronic periodontitis. The phenotypic and genetic features of strain SP18_26T were compared to those of the type species of Tannerella, Tannerella forsythia. A genome size of 2.97 Mbp (G+C content 56.5 mol%) was previously reported for SP18_26T, compared to a size of 3.28 Mbp (47.1 mol%) in T. forsythia ATCC 43037T. 16S rRNA gene sequence comparisons also revealed 94.3 % sequence identity with T. forsythia ATCC 43037T. Growth was stimulated by supplementation of media with N-acetyl muramic acid, as seen with T. forsythia, but the cells displayed a distinctive snake-like morphology. Fatty acid methyl ester analysis revealed a profile differing from T. forsythia, chiefly in the amount of 3-OH-16 : 0 (four-fold lower in SP18_26T). Overall, metabolic enzyme activity also differed from T. forsythia, with enzyme activity for indole present, but the complement of glycoside hydrolase enzyme activity was smaller than T. forsythia, for example, lacking sialidase and N-acetyl-ß-glucosaminidase - evidence backed up by analysis of its gene content. On the basis of these results, a new species Tannerella serpentiformis is proposed for which the type strain is SP18_26T (=DSM 102894T=JCM 31303T).

Dietary nitrate improves vascular function in patients with hypercholesterolemia: a randomized, double-blind, placebo-controlled study.

BACKGROUND: The beneficial cardiovascular effects of vegetables may be underpinned by their high inorganic nitrate content. OBJECTIVE: We sought to examine the effects of a 6-wk once-daily intake of dietary nitrate (nitrate-rich beetroot juice) compared with placebo intake (nitrate-depleted beetroot juice) on vascular and platelet function in untreated hypercholesterolemics. DESIGN: A total of 69 subjects were recruited in this randomized, double-blind, placebo-controlled parallel study. The primary endpoint was the change in vascular function determined with the use of ultrasound flow-mediated dilatation (FMD). RESULTS: Baseline characteristics were similar between the groups, with primary outcome data available for 67 patients. Dietary nitrate resulted in an absolute increase in the FMD response of 1.1% (an ∼24% improvement from baseline) with a worsening of 0.3% in the placebo group (P < 0.001). A small improvement in the aortic pulse wave velocity (i.e., a decrease of 0.22 m/s; 95% CI: -0.4, -0.3 m/s) was evident in the nitrate group, showing a trend (P = 0.06) to improvement in comparison with the placebo group. Dietary nitrate also caused a small but significant reduction (7.6%) in platelet-monocyte aggregates compared with an increase of 10.1% in the placebo group (P = 0.004), with statistically significant reductions in stimulated (ex vivo) P-selectin expression compared with the placebo group (P < 0.05) but no significant changes in unstimulated expression. No adverse effects of dietary nitrate were detected. The composition of the salivary microbiome was altered after the nitrate treatment but not after the placebo treatment (P < 0.01). The proportions of 78 bacterial taxa were different after the nitrate treatment; of those taxa present, 2 taxa were responsible for >1% of this change, with the proportions of Rothia mucilaginosa trending to increase and Neisseria flavescens (P < 0.01) increased after nitrate treatment relative to after placebo treatment. CONCLUSIONS: Sustained dietary nitrate ingestion improves vascular function in hypercholesterolemic patients. These changes are associated with alterations in the oral microbiome and, in particular, nitrate-reducing genera. Our findings provide additional support for the assessment of the potential of dietary nitrate as a preventative strategy against atherogenesis in larger cohorts. This trial was registered at clinicaltrials.gov as NCT01493752.

Fretibacterium fastidiosum gen. nov., sp. nov., isolated from the human oral cavity.

SGP1(T), a strain belonging to a lineage of the phylum Synergistetes with no previously cultivated representatives was subjected to a comprehensive range of phenotypic and genotypic tests. For good growth the strain was dependent on co-culture with, or extracts from, selected other oral bacteria. Cells of strain SGP1(T) were asaccharolytic and major amounts of acetic acid and moderate amounts of propionic acid were produced as end products of metabolism in peptone-yeast extract-glucose broth supplemented with a filtered cell sonicate of Fusobacterium nucleatum subsp. nucleatum ATCC 25586(T) (25 %, v/v). Hydrogen sulphide was produced and gelatin was weakly hydrolysed. The major cellular fatty acids were C(14 : 0), C(18 : 0) and C(16 : 0). The DNA G+C content of strain SGP1(T) was 63 mol%. Phylogenetic analysis of the full-length 16S rRNA gene showed that strain SGP1(T) represented a novel group within the phylum Synergistetes. A novel species in a new genus, Fretibacterium fastidiosum gen. nov., sp. nov., is proposed. The type strain of Fretibacterium fastidiosum is SGP1(T) ( = DSM 25557(T) = JCM 16858(T)).

Generation of diversity in Streptococcus mutans genes demonstrated by MLST.

Streptococcus mutans, consisting of serotypes c, e, f and k, is an oral aciduric organism associated with the initiation and progression of dental caries. A total of 135 independent Streptococcus mutans strains from caries-free and caries-active subjects isolated from various geographical locations were examined in two versions of an MLST scheme consisting of either 6 housekeeping genes [accC (acetyl-CoA carboxylase biotin carboxylase subunit), gki (glucokinase), lepA (GTP-binding protein), recP (transketolase), sodA (superoxide dismutase), and tyrS (tyrosyl-tRNA synthetase)] or the housekeeping genes supplemented with 2 extracellular putative virulence genes [gtfB (glucosyltransferase B) and spaP (surface protein antigen I/II)] to increase sequence type diversity. The number of alleles found varied between 20 (lepA) and 37 (spaP). Overall, 121 sequence types (STs) were defined using the housekeeping genes alone and 122 with all genes. However pi, nucleotide diversity per site, was low for all loci being in the range 0.019-0.007. The virulence genes exhibited the greatest nucleotide diversity and the recombination/mutation ratio was 0.67 [95% confidence interval 0.3-1.15] compared to 8.3 [95% confidence interval 5.0-14.5] for the 6 concatenated housekeeping genes alone. The ML trees generated for individual MLST loci were significantly incongruent and not significantly different from random trees. Analysis using ClonalFrame indicated that the majority of isolates were singletons and no evidence for a clonal structure or evidence to support serotype c strains as the ancestral S. mutans strain was apparent. There was also no evidence of a geographical distribution of individual isolates or that particular isolate clusters were associated with caries. The overall low sequence diversity suggests that S. mutans is a newly emerged species which has not accumulated large numbers of mutations but those that have occurred have been shuffled as a consequence of intra-species recombination generating genotypes which can be readily distinguished by sequence analysis.