Abstract
Lactobacillus represents a versatile bacterial genus, which can adapt to a wide variety of ecological niches, including human body sites such as the intestinal and urogenital tract. In this study, the complete genome sequence of the vaginal probiotic Lactobacillus rhamnosus GR-1 was determined and compared to other L. rhamnosus strains at genomic and phenotypic level. The strain GR-1 was originally isolated from a female urethra, and was assessed with L. rhamnosus GG from a feces sample of a healthy male, and L. rhamnosus LC705 from a dairy product. A key difference is the absence in GR-1 and LC705 of the spaCBA locus required for pili-mediated intestinal epithelial adhesion. In addition, the L. rhamnosus GR-1 genome contains a unique cluster for exopolysaccharide production, which is postulated to synthesize glucose-rich, rhamnose-lacking exopolysaccharide molecules that are different from the galactose-rich extracellular polysaccharide of L. rhamnosus GG. Compared to L. rhamnosus GG, L. rhamnosus GR-1 was also genetically predicted and experimentally shown to better metabolize lactose and maltose, and to better withstand oxidative stress, which is of relevance in the vagina. This study could thus provide a molecular framework for the selection of the optimal probiotic strain for each targeted niche and condition, but further substantiation of niche adaptation mechanisms of lactobacilli is warranted.
Highlights
The importance of Lactobacillus species in promoting a healthy ecosystem in the human vagina has been well-recognized (Bruce et al, 1973; Petrova et al, 2015)
The draft genome sequence of L. rhamnosus GR-1 was determined based on the assembly of 266 contigs, and found to have a genome size of 2.89 Mbp, a whole genome GC % of 46.48% and a total of 2,714 predicted genes
We report that L. rhamnosus GR-1 has a genome size of 2.91 Mbp, in agreement with other L. rhamnosus strains
Summary
The importance of Lactobacillus species in promoting a healthy ecosystem in the human vagina has been well-recognized (Bruce et al, 1973; Petrova et al, 2015). The ability to replenish an aberrant vaginal microbiota with exogenous lactobacilli as probiotics was first reported in 1988 using Lactobacillus rhamnosus GR-1 (Bruce and Reid, 1988). The strain has been shown to temporarily colonize the human vagina (Gardiner et al, 2002) and intestine in vivo following oral uptake (Reid et al, 2003). The fact that oral application of L. rhamnosus GR-1 can result in vaginal colonization is of interest in view of the natural ascension of lactobacilli from the gastro-intestinal to the vaginal tract
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