Ruthenibacterium lactatiformans gen. nov., sp.nov., an anaerobic, lactate-producing member of the family Ruminococcaceae isolated from human faeces

Two novel strains of Gram-stain-negative, rod-shaped, obligately anaerobic, non-spore-forming, non-motile bacteria were isolated from the faeces of healthy human subjects. The strains, designated as 585-1T and 668, were characterized by mesophilic fermentative metabolism, production of d-lactic acid, succinic acid and acetic acid as end products of d-glucose fermentation, prevalence of C18 : 1 ω9, C18 : 1 ω9 aldehyde, C16 : 0 and C16 : 1 ω7c fatty acids, presence of glycine, glutamic acid, lysine, alanine and aspartic acid in the petidoglycan peptide moiety and lack of respiratory quinones. Whole genome sequencing revealed the DNA G+C content was 56.4–56.6 mol%. The complete 16S rRNA gene sequences of the two strains shared 91.7/91.6 % similarity with Anaerofilum pentosovorans FaeT, 91.3/91.2 % with Gemmiger formicilis ATCC 27749T and 88.9/88.8 % with Faecalibacterium prausnitzii ATCC 27768T. On the basis of chemotaxonomic and genomic properties it was concluded that the strains represent a novel species in a new genus within the family Ruminococcaceae , for which the name Ruthenibacterium lactatiformans gen. nov., sp. nov. is proposed. The type strain of Ruthenibacterium lactatiformans is 585-1T (=DSM 100348T=VKM B-2901T)

Comparative analysis of Faecalibacterium prausnitzii genomes shows a high level of genome plasticity and warrants separation into new species-level taxa

peer-reviewedBackground Faecalibacterium prausnitzii is a ubiquitous member of the human gut microbiome, constituting up to 15% of the total bacteria in the human gut. Substantial evidence connects decreased levels of F. prausnitzii with the onset and progression of certain forms of inflammatory bowel disease, which has been attributed to its anti-inflammatory potential. Two phylogroups of F. prausnitzii have been identified, with a decrease in phylogroup I being a more sensitive marker of intestinal inflammation. Much of the genomic and physiological data available to date was collected using phylogroup II strains. Little analysis of F. prausnitzii genomes has been performed so far and genetic differences between phylogroups I and II are poorly understood. Results In this study we sequenced 11 additional F. prausnitzii genomes and performed comparative genomics to investigate intraspecies diversity, functional gene complement and the mobilome of 31 high-quality draft and complete genomes. We reveal a very low level of average nucleotide identity among F. prausnitzii genomes and a high level of genome plasticity. Two genomogroups can be separated based on differences in functional gene complement, albeit that this division does not fully agree with separation based on conserved gene phylogeny, highlighting the importance of horizontal gene transfer in shaping F. prausnitzii genomes. The difference between the two genomogroups is mainly in the complement of genes associated with catabolism of carbohydrates (such as a predicted sialidase gene in genomogroup I) and amino acids, as well as defense mechanisms. Conclusions Based on the combination of ANI of genomic sequences, phylogenetic analysis of core proteomes and functional differences we propose to separate the species F. prausnitzii into two new species level taxa: F. prausnitzii sensu stricto (neotype strain A2–165T = DSM 17677T = JCM 31915T) and F. moorei sp. nov. (type strain ATCC 27768T = NCIMB 13872T).This research was conducted with the financial support of Science Foundation Ireland (SFI) under Grant Number SFI/12/RC/2273, a Science Foundation Ireland’s Spokes Programme which is co-funded under the European Regional Development Fund under Grant Number SFI/14/SP APC/B3032, and a research grant from Janssen Biotech, Inc

Distribution of ortholog groups by the number of strains in which they are present.

<p>Ortholog groups were divided into three categories based on their prevalence.</p

Structure of CRISPR-Cas systems in <i>B</i>. <i>longum</i>.

<p>Each scheme represents a typical locus from one of the studied strains.</p

Pairwise comparison of ortholog groups content in <i>B</i>. <i>longum</i> strains.

<p>Heatmap represents the number of shared orthologs between strains, the tree was inferred by complete linkage hierarchical clustering.</p

Strains, isolated from the same children in different time points.

<p>Horizontal axis represent the age of the subject, rows represent the children, labels in the cells correspond to the isolated strains. Dotted lines connect similar strains.</p

Intraspecies Genomic Diversity and Long-Term Persistence of <i>Bifidobacterium longum</i>

<div><p>Members of genus <i>Bifidobacterium</i> are Gram-positive bacteria, representing a large part of the human infant microbiota and moderately common in adults. However, our knowledge about their diversity, intraspecific phylogeny and long-term persistence in humans is still limited. <i>Bifidobacterium longum</i> is generally considered to be the most common and prevalent species in the intestinal microbiota. In this work we studied whole genome sequences of 28 strains of <i>B</i>. <i>longum</i>, including 8 sequences described in this paper. Part of these strains were isolated from healthy children during a long observation period (up to 10 years between isolation from the same patient). The three known subspecies (<i>longum</i>, <i>infantis</i> and <i>suis</i>) could be clearly divided using sequence-based phylogenetic methods, gene content and the average nucleotide identity. The profiles of glycoside hydrolase genes reflected the different ecological specializations of these three subspecies. The high impact of horizontal gene transfer on genomic diversity was observed, which is possibly due to a large number of prophages and rapidly spreading plasmids. The pan-genome characteristics of the subspecies <i>longum</i> corresponded to the open pan-genome model. While the major part of the strain-specific genetic loci represented transposons and phage-derived regions, a large number of cell envelope synthesis genes were also observed within this category, representing high variability of cell surface molecules. We observed the cases of isolation of high genetically similar strains of <i>B</i>. <i>longum</i> from the same patients after long periods of time, however, we didn’t succeed in the isolation of genetically identical bacteria: a fact, reflecting the high plasticity of microbiota in children.</p></div

Small cryptic plasmids from <i>B</i>. <i>longum</i> strains sequenced for this study.

<p>Small cryptic plasmids from <i>B</i>. <i>longum</i> strains sequenced for this study.</p

Total numbers of IS elements of different families in the complete <i>B</i>. <i>longum</i> genome sequences.

<p>Total numbers of IS elements of different families in the complete <i>B</i>. <i>longum</i> genome sequences.</p