Acquisition and Adaptation of Ultra-small Parasitic Reduced Genome Bacteria to Mammalian Hosts.

The first cultivated representative of the enigmatic phylum Saccharibacteria (formerly TM7) was isolated from humans and revealed an ultra-small cell size (200-300 nm), a reduced genome with limited biosynthetic capabilities, and a unique parasitic lifestyle. TM7x was the only cultivated member of the candidate phyla radiation (CPR), estimated to encompass 26% of the domain Bacteria. Here we report on divergent genomes from major lineages across the Saccharibacteria phylum in humans and mammals, as well as from ancient dental calculus. These lineages are present at high prevalence within hosts. Direct imaging reveals that all groups are ultra-small in size, likely feeding off commensal bacteria. Analyses suggest that multiple acquisition events in the past led to the current wide diversity, with convergent evolution of key functions allowing Saccharibacteria from the environment to adapt to mammals. Ultra-small, parasitic CPR bacteria represent a relatively unexplored paradigm of prokaryotic interactions within mammalian microbiomes.

Toll-like receptor-2 and -4 responses regulate neutrophil infiltration into the junctional epithelium and significantly contribute to the composition of the oral microbiota.

BACKGROUND: Oral gingival tissue, especially the junctional epithelium (JE), is constantly exposed to sub-gingival plaque. A key component of gingival health is the regulation of the number of neutrophils that migrate into the gingival crevice to counteract its harmful effects. This report investigates the contribution of innate defense receptors, Toll-like receptor (TLR)2, TLR4, and both (TLR2/4) to the maintenance of neutrophil homeostasis in the JE. METHODS: Bacterial composition was analyzed from whole oral swabs collected from 12- to 14-week-old TLR2, TLR4, TLR2/4 double knock-out (KO) mice using a MiSeq platform targeting the V3-V4 region of the 16S ribosomal RNA gene. Mandibles were histologically examined for quantification of neutrophils in the JE and bone loss. Lastly, total bacterial load was quantitated using quantitative real-time PCR. RESULTS: Compared with wild-type, all TLR KO mice displayed significantly increased recruitment of neutrophils (P = 0.0079) into the JE. In addition, TLR4 and TLR2/4 KO mice demonstrated a significant increase in the number of bacteria (P = 0.0022 and P = 0.0152, respectively). Lastly, comparative compositional analyses of the oral microbiome revealed that each KO strain harbored unique microbial communities that are distinct from each other but maintained similar levels of alveolar bone. CONCLUSIONS: Neutrophil migration into healthy mouse JE does not require TLR2 or TLR4. However, a significant increase in the number of neutrophils as well as a significant change in the oral microbial composition in both TLR2 and TLR4 KO mice demonstrate that these TLRs contribute to the homeostatic relationship between bacteria and the host in healthy mice periodontal tissue.

Draft Genome Sequence of Low-Passage Clinical Isolate Porphyromonas gingivalis MP4-504.

We present the draft genome ofPorphyromonas gingivalisMP4-504, a low-passage clinical isolate obtained from a periodontitis patient. The genome is composed of 92 contigs for a length of 2,373,453 bp and a G+C of 48.3%. ThetraA-Qconjugative transfer locus is genetically distinct from W83 but highly similar to ATCC 33277.

Draft Genome Sequence of Actinomyces odontolyticus subsp. actinosynbacter Strain XH001, the Basibiont of an Oral TM7 Epibiont.

Here, we present the draft genome sequence of Actinomyces odontolyticus subsp. actinosynbacter strain XH001, isolated from the human oral cavity. Uniquely, it was discovered as a host bacterium to the ultrasmall epibiont TM7x, which is the first cultivated member of "Candidatus Saccharibacteria" (formerly candidate phylum TM7).