Plasmid transduction using bacteriophage Phi(adh) for expression of CC chemokines by Lactobacillus gasseri ADH

Current State of Microbicide Development

Efforts in developing an effective vaccine for human immunodeficiency virus (HIV) has been challenging as HIV strains are highly variable and exhibit extraordinary mutability. Despite condom usage and pre-exposure prophylaxis as excellent prevention strategies, lack of accessibility in some developing countries and low adherence due to sociocultural factors continue to act as barriers in reducing the HIV epidemic. Microbicides are topical therapies developed to prevent HIV and other sexually transmitted infections during intercourse. Microbicides applied vaginally or rectally are intended to prevent HIV infection at the site of transmission by either inhibiting its entry into immune cells or prevent viral replication. This review will summarize some of the current state-of-the-art microbicide formulations that are in preclinical and clinical stages of development and discuss some of the challenges associated with microbicide development.

Identification and sequence analysis of two novel cryptic plasmids isolated from the vaginal mucosa of South African women

The vaginal mucosa is dominated by Gram positive, rod shaped lactobacilli which serve as a natural barrier against infection. In both healthy- and bacterial vaginosis (BV)-infected women Lactobacillus crispatus and Lactobacillus jensenii have been found to be the predominant Lactobacillus species. Many studies have been conducted to assess factors influencing lactobacilli dominance in the vaginal microbiome. In the present study two plasmids, pLc4 and pLc17, isolated from vaginal Lactobacillus strains of both healthy and BV-infected women were characterized. The smaller plasmid, pLc4 (4224 bp), was detected in both L. crispatus and L. jensenii strains, while pLc17 was only detected in L. crispatus. Based on its nucleotide sequence pLc4 appears highly novel, with its replication protein having 44% identity to the replication initiation protein of pSMQ173b_03. Phylogenetic analysis with other Rolling Circle Replication plasmids confirmed that pLc4 shows a low degree of similarity to these plasmids. Plasmid pLc17 (16,663 bp) appears to carry both a RCR replicon and a theta replicon, which is rare in naturally occurring plasmids. pLc4 was maintained at a high copy number of 29, while pLc17 appears to be a medium copy number plasmid maintained at 11 copies per chromosome. While sequence analysis is a valuable tool to study cryptic plasmids, further function-based analysis will be required in order to fully elucidate the role of these plasmids within the vaginal milieu.

Spontaneously induced prophages in Lactobacillus gasseri contribute to horizontal gene transfer

Lactobacillus gasseri is an endogenous species of the human gastrointestinal tract and vagina. With recent advances in microbial taxonomy, phylogenetics, and genomics, L. gasseri is recognized as an important commensal and is increasingly being used in probiotic formulations. L. gasseri strain ADH is lysogenic and harbors two inducible prophages. In this study, prophage adh was found to spontaneously induce in broth cultures to populations of ∼ 10(7) PFU/ml by stationary phase. The adh prophage-cured ADH derivative NCK102 was found to harbor a new, second inducible phage, vB_Lga_jlb1 (jlb1). Phage jlb1 was sequenced and found to be highly similar to the closely related phage LgaI, which resides as two tandem prophages in the neotype strain L. gasseri ATCC 33323. The common occurrence of multiple prophages in L. gasseri genomes, their propensity for spontaneous induction, and the high degree of homology among phages within multiple species of Lactobacillus suggest that temperate bacteriophages likely contribute to horizontal gene transfer (HGT) in commensal lactobacilli. In this study, the host ranges of phages adh and jlb1 were determined against 16 L. gasseri strains. The transduction range and the rate of spontaneous transduction were investigated in coculture experiments to ascertain the degree to which prophages can promote HGT among a variety of commensal and probiotic lactobacilli. Both adh and jlb1 particles were confirmed to mediate plasmid transfer. As many as ∼10(3) spontaneous transductants/ml were obtained. HGT by transducing phages of commensal lactobacilli may have a significant impact on the evolution of bacteria within the human microbiota.

Recent progress in engineering human-associated microbiomes

Recent progress in molecular biology and genetics opens up the possibility of engineering a variety of biological systems, from single-cellular to multicellular organisms. The consortia of microbes that reside on the human body, the human-associated microbiota, are particularly interesting as targets for forward engineering and manipulation due to their relevance in health and disease. New technologies in analysis and perturbation of the human microbiota will lead to better diagnostic and therapeutic strategies against diseases of microbial origin or pathogenesis. Here, we discuss recent advances that are bringing us closer to realizing the true potential of an engineered human-associated microbial community.

Genomic and phenotypic evidence for probiotic influences of Lactobacillus gasseri on human health

Certain lactic acid bacteria (LAB) have the capacity to occupy mucosal niches of humans, including the oral cavity, gastrointestinal tract, and vagina. Among commensal, LAB are species of the acidophilus complex, which have proven to be a substantial reservoir for microorganisms with probiotic attributes. Specifically, Lactobacillus gasseri is an autochthonous microorganism which has been evaluated for probiotic activity based on the availability of genome sequence and species-specific adaptation to the human mucosa. Niche-related characteristics of L. gasseri contributing to indigenous colonization include tolerance of low pH environments, resistance to bile salts, and adhesion to the host epithelium. In humans, L. gasseri elicits various health benefits through its antimicrobial activity, bacteriocin production, and immunomodulation of the innate and adaptive systems. The genomic and empirical evidence supporting use of L. gasseri in probiotic applications is substantiated by clinical trial data displaying maintenance of vaginal homeostasis, mitigation of Helicobacter pylori infection, and amelioration of diarrhea.

Identification of predominant culturable vaginal Lactobacillus species and associated bacteriophages from women with and without vaginal discharge syndrome in South Africa

Lactobacillus jensenii, Lactobacillus crispatus, Lactobacillus iners, Lactobacillus gasseri and Lactobacillus vaginalis were identified by 16S rRNA gene sequencing as the predominant culturable vaginal Lactobacillus species in a group of South African women, comprising 24, 22, 10, 10 and 9 %, respectively. A significant effect of vaginal discharge syndrome (VDS) and bacterial vaginosis (BV) on the distribution of predominant Lactobacillus species was observed. Whilst L. crispatus isolates were almost equally distributed between individuals with and without VDS and were not significantly reduced in women with BV versus normal microflora, L. jensenii isolates were significantly reduced in women with VDS (P=0.022) and reduced in women with BV versus normal microflora (P=0.053). Unlike L. crispatus, L. jensenii isolates were also significantly reduced in women with BV-associated VDS versus women without VDS and with normal microflora (P=0.051). In addition, lysogeny was commonly observed for L. crispatus, with 77 % of isolates yielding phage particles with contractile and non-contractile tails. Only 29 % of L. jensenii isolates yielded phage particles, and these were visible as tailless or podo-like particles.