'Lactobacillus fermentum' 3872 as a potential tool for combatting 'Campylobacter jejuni' infections

Due to the global spread of multidrug resistant pathogenic bacteria, alternative approaches in combating infectious diseases are required. One such approach is the use of probiotics. Lactobacillus fermentum 3872 is a promising probiotic bacterium producing a range of antimicrobial compounds, such as hydrogen peroxide and lactic acid. In addition, previous studies involving genome sequencing and analysis of L. fermentum 3872 allowed the identification of a gene encoding a cell surface protein referred to as collagen binding protein (CBP) (not found in other strains of the species, according to the GenBank database), consisting of a C-terminal cell wall anchor domain (LPXT), multiple repeats of ‘B domains' that form stalks presenting an “A domain” required for adhesion. In this study, we found that the CBP of L. fermentum 3872 binds to collagen I present on the surface of the epithelial cells lining the gastrointestinal tract. Moreover, we found that this host receptor is also used for attachment by the major gastrointestinal pathogen, Campylobacter jejuni. Furthermore, we identified an adhesin involved in such interaction and demonstrated that both L. fermentum 3872 and its CBP can inhibit binding of this pathogen to collagen I. Combined with the observation that C. jejuni growth is affected in the acidic environment produced by L. fermentum 3872, the finding provides a good basis for further investigation of this strain as a potential tool for fighting Campylobacter infections

' Lactobacillus fermentum ' 3872 genome sequencing reveals plasmid and chromosomal genes potentially involved in a probiotic activity.

In this report we describe a ' Lactobacillus fermentum ' 3872 plasmid (pLF3872) not previously found in any other strain of this species. The analysis of the complete sequence of this plasmid revealed the presence of a gene encoding a large collagen binding protein (CBP), as well as the genes responsible for plasmid maintenance and conjugation. Potential roles of CBP and a chromosomally encoded fibronectin-binding protein (FbpA) in probiotic activity are discussed

MdaB and NfrA, Two novel reductases important in the survival and persistence of the major enteropathogen Campylobacter jejuni

The paralogues RrpA and RrpB, which are members of the MarR family of DNA binding proteins, are important for the survival of the global bacterial foodborne pathogen Campylobacter jejuni under redox stress. We report that RrpA is a positive regulator of mdaB, encoding a flavin-dependent quinone reductase that contributes to the protection from redox stress mediated by structurally diverse quinones, while RrpB negatively regulates the expression of cj1555c (renamed nfrA for NADPH-flavin reductase A), encoding a flavin reductase. NfrA reduces riboflavin at a greater rate than its derivatives, suggesting that exogenous free flavins are the natural substrate. MdaB and NfrA both prefer NADPH as an electron donor. Cysteine substitution and posttranslational modification analyses indicated that RrpA and RrpB employ a cysteine-based redox switch. Complete genome sequence analyses revealed that mdaB is frequently found in Campylobacter and related Helicobacter spp., while nfrA is predominant in C. jejuni strains. Quinones and flavins are redox cycling agents secreted by a wide range of cell types that can form damaging superoxide by one-electron reactions. We propose a model for stress adaptation where MdaB and NfrA facilitate a two-electron reduction mechanism to the less toxic hydroquinones, thus aiding survival and persistence of this major pathogen. IMPORTANCE Changes in cellular redox potential result in alteration in the oxidation state of intracellular metabolites and enzymes; consequently, cells make adjustments that favor growth and survival. The work we present here answers some of the many questions that have remained elusive over the years of investigation into the enigmatic microaerophile bacterium Campylobacter jejuni. We employed molecular approaches to understand the regulation mechanisms and functional analyses to reveal the roles of two novel quinone and flavin reductases; both serve as major pools of cellular redox-active molecules. This work extends our knowledge on bacterial redox sensing mechanisms and the significance of hemostasis

Biotechnological and ecological potential of 'Micromonospora provocatoris' sp. nov., a gifted strain isolated from the Challenger Deep of the Mariana Trench

A Micromonospora strain, isolate MT25T, was recovered from a sediment collected from the Challenger Deep of the Mariana Trench using a selective isolation procedure. The isolate produced two major metabolites, n-acetylglutaminyl glutamine amide and desferrioxamine B, the chemical structures of which were determined using 1D and 2D-NMR, including 1H-15N HSQC and 1H-15N HMBC 2D-NMR, as well as high resolution MS. A whole genome sequence of the strain showed the presence of ten natural product-biosynthetic gene clusters, including one responsible for the biosynthesis of desferrioxamine B. Whilst 16S rRNA gene sequence analyses showed that the isolate was most closely related to the type strain of Micromonospora chalcea, a whole genome sequence analysis revealed it to be most closely related to Micromonospora tulbaghiae 45142T. The two strains were distinguished using a combination of genomic and phenotypic features. Based on these data, it is proposed that strain MT25T (NCIMB 15245T, TISTR 2834T) be classified as Micromonospora provocatoris sp. nov. Analysis of the genome sequence of strain MT25T (genome size 6.1 Mbp) revealed genes predicted to responsible for its adaptation to extreme environmental conditions that prevail in deep-sea sediments

Discovery and characterisation of a novel plasmid of a probiotic strain Lactobacillus fermentum 3872

Previous in vitro studies have demonstrated the outstanding probiotic properties of Lactobacillus fermentum strain 3872, which include enhanced antibacterial activities and the ability to adhere to various tissue culture cell lines (unpublished observations). The molecular basis for these properties and factors involved remained unknown until a draft genome sequencing of this bacterium became available (1). In particular, a partial sequence of a gene encoding an unusually large collagen-binding protein (CBP) has been reported (1). In this study we discovered and characterised plasmid pLF3872 carrying this and other genes that may be essential for the antibacterial properties of this microorganism. The complete sequence of the plasmid was derived in the course of a genome sequencing project using Ion Torrent PGM and 400nt sequencing kit. In addition to cbp, this circular 32 kb plasmid also contains thirty two other genes, including those encoding a toxin-antitoxin pair required for a stable maintenance of the plasmid within the strain. There is also a gene encoding a peptidoglycan hydrolase with a potential role in conjugation. The collagen binding protein encoded by the cbp gene was found to contain five repetitive ‘B domains’. These domains may be involved in the formation of a ‘stalk’ presenting a non-repetitive ‘A domain’ involved in adhesin. Interestingly, 3872 is the only strain of L. fermentum carrying the cbp gene. The CBPs produced by some other Lactobacillus spp contain only four B domains. Such adhesins are also produced by some pathogenic bacteria, e.g. Staphylococcus aureus which may explain the mechanism of a probiotic action based on competitive exclusion during attachment to host cells (2). The ability to produce a collagen binding protein may also allow the probiotic to compete against pathogenic bacteria bound to the same target protein resulting in colonisation of the site of infection followed by the release antimicrobial substances (such as bacteriocins and hydrogen peroxide)