Preliminary landscape of Candidatus Saccharibacteria in the human microbiome.

Introduction: Candidate Phyla Radiation (CPR) and more specifically Candidatus Saccharibacteria (TM7) have now been established as ubiquitous members of the human oral microbiota. Additionally, CPR have been reported in the gastrointestinal and urogenital tracts. However, the exploration of new human niches has been limited to date. Methods: In this study, we performed a prospective and retrospective screening of TM7 in human samples using standard PCR, real-time PCR, scanning electron microscopy (SEM) and shotgun metagenomics. Results: Using Real-time PCR and standard PCR, oral samples presented the highest TM7 prevalence followed by fecal samples, breast milk samples, vaginal samples and urine samples. Surprisingly, TM7 were also detected in infectious samples, namely cardiac valves and blood cultures at a low prevalence (under 3%). Moreover, we observed CPR-like structures using SEM in all sample types except cardiac valves. The reconstruction of TM7 genomes in oral and fecal samples from shotgun metagenomics reads further confirmed their high prevalence in some samples. Conclusion: This study confirmed, through their detection in multiple human samples, that TM7 are human commensals that can also be found in clinical settings. Their detection in clinical samples warrants further studies to explore their role in a pathological setting.

Peptostreptococcus faecalis sp. nov., new bacterial species isolated from healthy indigenous congolese volunteer.

The Microbial Culturomics Project aiming to discover several bacterial species made it possible to isolate the strain Marseille-P4308T from a stool sample of a healthy indigenous Congolese volunteer. Strain Marseille-P4308T is a Gram-positive coccus shaped bacterium that optimally grows at 37 °C. The 16S rRNA gene sequence of the strain has a 96.2% sequence similarity to Peptostreptococcus anaerobius strain NCTC 11460T (GenBank accession number: NR_042847.1). In addition, the average nucleotide identity of strain Marseille-P4308T with its closest related species was 71.1%, which was far below the recommended threshold (>95-96%). The genome of the strain Marseille-P4308T has a length of 2.14 Mbp with G + C content of 30.4 mol%. Based on phenotypic, biochemical, genomic and phylogenetic analysis, strain Marseille-P4308T (= CSUR P4308 = CECT 9960) clearly appears to be a new species for which the name Peptostreptococcus faecalis sp. nov., is proposed.

Deciphering the Urinary Microbiota Repertoire by Culturomics Reveals Mostly Anaerobic Bacteria From the Gut.

Human urine was considered sterile for a long time. However, 416 species have been previously cultured, including only 40 anaerobic species. Here, we used culturomics, particularly those targeting anaerobes, to better understand the urinary microbiota. By testing 435 urine samples, we isolated 450 different bacterial species, including 256 never described in urine of which 18 were new species. Among the bacterial species identified, 161 were anaerobes (35%). This study increased the known urine repertoire by 39%. Among the 672 bacterial species isolated now at least once from urine microbiota, 431 (64.1%) were previously isolated from gut microbiota, while only 213 (31.7%) were previously isolated from vagina. These results suggest that many members of the microbiota in the urinary tract are in fact derived from the gut, and a paradigm shift is thus needed in our understanding.