Abstract
Bacterial vaginosis-associated bacterium 1 (BVAB1) is an as-yet uncultured bacterial species found in the human vagina that belongs to the family Lachnospiraceae within the order Clostridiales. As its name suggests, this bacterium is often associated with bacterial vaginosis (BV), a common vaginal disorder that has been shown to increase a woman's risk for HIV, Chlamydia trachomatis, and Neisseria gonorrhoeae infections as well as preterm birth. BVAB1 has been further associated with the persistence of BV following metronidazole treatment, increased vaginal inflammation, and adverse obstetrics outcomes. There is no available complete genome sequence of BVAB1, which has made it difficult to mechanistically understand its role in disease. We present here a circularized metagenome-assembled genome (cMAG) of BVAB1 as well as a comparative analysis including an additional six metagenome-assembled genomes (MAGs) of this species. These sequences were derived from cervicovaginal samples of seven separate women. The cMAG was obtained from a metagenome sequenced with long-read technology on a PacBio Sequel II instrument while the others were derived from metagenomes sequenced on the Illumina HiSeq platform. The cMAG is 1.649 Mb in size and encodes 1,578 genes. We propose to rename BVAB1 to “Candidatus Lachnocurva vaginae” based on phylogenetic analyses, and provide genomic and metabolomic evidence that this candidate species may metabolize D-lactate, produce trimethylamine (one of the chemicals responsible for BV-associated odor), and be motile. The cMAG and the six MAGs are valuable resources that will further contribute to our understanding of the heterogeneous etiology of bacterial vaginosis.
Highlights
Bacterial vaginosis (BV) is a common vaginal infection affecting approximately 30% of US reproductive-aged women, with both African- and Mexican-Americans disproportionately afflicted (Allsworth and Peipert, 2007; Koumans et al, 2007)
A phylogenetic analysis using the full-length 16S rRNA genes extracted from all metagenome-assembled genomes (MAGs) revealed Bacterial vaginosis-associated bacterium 1 (BVAB1) belongs in the Clostridales family Lachnospiraceae, and that S. satelles is the closest known relative (Figure 1), though nucleotide identity is only 89.2%
We present here a circularized MAG of “Ca. Lachnocurva vaginae” and six MAGs of the candidate species, previously known as BVAB1, an important member of the human vaginal microbiota associated with bacterial vaginosis and other adverse outcomes
Summary
Bacterial vaginosis (BV) is a common vaginal infection affecting approximately 30% of US reproductive-aged women, with both African- and Mexican-Americans disproportionately afflicted (Allsworth and Peipert, 2007; Koumans et al, 2007). A critical step along the path to understanding the ecology and pathogenic potential of a bacterial species is the characterization of its genome. BVAB1 was first identified by Fredricks et al (2005) using 16S rRNA gene amplicons Sanger sequencing of samples associated with BV, and has eluded cultivation efforts since. Vaginal communities in which BVAB1 16S rRNA gene sequence is detected have been associated with vaginal inflammation and persistent BV in African women (Lennard et al, 2018). BVAB1 remains uncultured and aside from detection of this species via partial 16S rRNA gene amplicon sequencing, little is known about its metabolism, pathogenic potential, or ecology in the vaginal environment, especially during BV. A 94 contig BVAB1 metagenome-assembled genome from short-read sequencing was produced (Fettweis et al, 2019)
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