Hemagglutination activity of Lactobacillus acidophilus group lactic acid bacteria

Cloning, expression and characterization of a mucin-binding GAPDH from Lactobacillus acidophilus

Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) is a ubiquitous enzyme involved in glycolysis. It is also referred to as a moonlighting protein as it has many diverse functions like regulation of apoptosis, iron homeostasis, cell-matrix interactions, adherence to human colon etc. apart from its principal role in glycolysis. Lactobacilli are lactic acid bacteria which colonize the human gut and confer various health benefits to humans. In the present study, we have cloned, expressed and purified the GAPDH from Lactobacillus acidophilus to get a recombinant product (r-LaGAPDH) and characterized it. Size exclusion chromatography shows that r-LaGAPDH exists as a tetramer in solution and have a mucin binding and hemagglutination activity indicating carbohydrate like binding adhesion mechanism. Fluorescence spectroscopy studies showed an interaction of r-LaGAPDH with mannose, galactose, N-acetylgalactosamine and N-acetylglucosamine with a Kd of 3.6±0.7×10(-3)M, 4.34±0.09×10(-3)M, 4±0.87×10(-3)M and 3.7±0.28×10(-3)M respectively. We hope that this preliminary data will generate more interest in further elucidation of the roles of GAPDH in the adhesion processes of the bacteria.

A New Assay Using Surface Plasmon Resonance (SPR) to Determine Binding of theLactobacillus acidophilusGroup to Human Colonic Mucin

A new binding assay to investigate the mechanism of adhesion of lactic acid bacteria to the human intestine was established by the surface plasmon resonance technique using a biosensor BIACORE1000. Cells of 26 strains of the Lactobacillus acidophilus group as analytes were eluted onto a sensor chip on which were immobilized biotinylated A-trisaccharide polymer probes having human A-type antigen [(GalNAcalpha1-3(Fucalpha1-2)Gal)-] or human colonic mucin of blood type A (HCM-A) as ligands. In the first screening, high adhesive affinity to the A-trisaccharide BP-probe was observed in L. acidophilus OLL2769, L. crispatus JCM8778, LA205 and LA206. In the second screening, which used HCM-A, only L. acidophilus OLL2769 and L. crispatus JCM8778 were selected as adhesive strains with specific binding ability to human A-antigen. The results indicated that some strains of the L. acidophilus group could recognize and bind the sugar chain of A-antigen structure on HCM.

Lactobacillus surface layer proteins: structure, function and applications

Bacterial surface (S) layers are the outermost proteinaceous cell envelope structures found on members of nearly all taxonomic groups of bacteria and Archaea. They are composed of numerous identical subunits forming a symmetric, porous, lattice-like layer that completely covers the cell surface. The subunits are held together and attached to cell wall carbohydrates by non-covalent interactions, and they spontaneously reassemble in vitro by an entropy-driven process. Due to the low amino acid sequence similarity among S-layer proteins in general, verification of the presence of an S-layer on the bacterial cell surface usually requires electron microscopy. In lactobacilli, S-layer proteins have been detected on many but not all species. Lactobacillus S-layer proteins differ from those of other bacteria in their smaller size and high predicted pI. The positive charge in Lactobacillus S-layer proteins is concentrated in the more conserved cell wall binding domain, which can be either N- or C-terminal depending on the species. The more variable domain is responsible for the self-assembly of the monomers to a periodic structure. The biological functions of Lactobacillus S-layer proteins are poorly understood, but in some species S-layer proteins mediate bacterial adherence to host cells or extracellular matrix proteins or have protective or enzymatic functions. Lactobacillus S-layer proteins show potential for use as antigen carriers in live oral vaccine design because of their adhesive and immunomodulatory properties and the general non-pathogenicity of the species.

Antimicrobial activity and protective properties of vaginal lactobacilli from healthy Bulgarian women

The role of vaginal Lactobacillus as an efficient barrier against invading pathogens is of considerable interest. The purpose of the present study was to assess in vitro the ability of 20 recently identified vaginal lactobacilli to protect the vagina. In order to evaluate their significance, the antimicrobial, hemagglutination (HA) and aggregation (Agg) activities, as well as acid and hydrogen peroxide (H(2)O(2)) production, were estimated. The cell-free cultures of eight strains showed a stable antimicrobial activity after elimination of the putative effects of lactic acid and H(2)O(2). Three of the isolated vaginal lactobacilli expressed a broad spectrum of anti-bacterial activity including Gram-negative pathogens. Strains with anti-Gardnerella and anti-herpes simplex virus type 2 activities were found. All tested isolates were H(2)O(2) producers, actively acidifying the growth media to pH 3.92+/-0.04, which is presumed to neutralize sexually transmitted infection pathogens. The major part (75%) expressed an HA activity and different Agg phenotypes, estimated as important properties in the competition with invading pathogens and in host defense. These results are encouraging and prompt further research of the characterized active strains and their possible application in prophylaxis of vaginal disorders.

Gradient diffusion antibiotic susceptibility testing of potentially probiotic lactobacilli

Minimum inhibitory contentrations (MICs) of selected inhibitors of cell wall synthesis (benzylpenicillin, ampicillin, and vancomycin), protein synthesis (gentamicin, streptomycin, tetracycline, chloramphenicol, and erythromycin), and nucleic acid synthesis (co-trimoxazole, rifampicin, and metronidazole) were determined by gradient diffusion (E test; AB Biodisk, Solna, Sweden) on deMan, Rogosa, Sharpe (MRS) agar for Lactobacillus strain GG and 11 closely related, rapidly growing, facultatively anaerobic, potentially probiotic Lactobacillus rhamnosus strains. All strains were resistant to vancomycin (MIC90 > or = 256 microg/ml), co-trimoxazole (MIC90 > or = 32 microg/ml), metronidazole (MIC90 > or = 32 microg/ml), gentamicin (MIC90 > or = 128 microg/ml), and streptomycin (MIC90 > or = 256 microg/ml), and sensitive to pencillin G (MIC90 > 0.375 microg/ml), ampicillin (MIC90 > 0.750 microg/ml), rifampicin (MIC90 > 0.375 microg/ml), tetracycline (MIC90 > 1.5 microg/ml), chloramphenicol (MIC90 > 8 microg/ml), and erythromycin (MIC90 > 2 microg/ml). E test MICs were also determined for L. acidophilus National Collection of Food Bacteria (NCFB) 1748 and L. reuteri Deutsche Sammlung von Mikroorganismen 20016T by the inoculum application method recommended by the manufacturer (swabbing), with and without antibiotic prediffusion for 1 h at room temperature, and by an alternative inoculum application (agar overlay) method, without antibiotic prediffusion. Antibiotic prediffusion increased the MICs for penicillin G, ampicillin, tetracycline, and chloramphenicol by up to 2 log2 MIC dilutions without changing antibiotic susceptibility category. Agar overlay application also increased the MICs for these antibiotics as well as for gentamicin by up to 3 log2 MIC dilutions without changing antibiotic susceptibility category. Exact agreement between MICs determined by swab and agar overlay application without antibiotic prediffusion was strain dependent: 54.5% for strain DSM 20016T and 72.7% for strain NCFB 1748. The swab and agar overlay gradient diffusion methods provide a reliable basis for antibiotic susceptibility testing of rapidly growing, facultatively anaerobic lactobacilli, using MRS agar as test medium and are readily applicable for testing individual isolates as needed.

Occurrence of lectins and hydrophobicity of bacteria obtained from biofilm of hospital catheters and water pipes

Bacteria isolated from biofilms of water distribution pipes and colonized catheters from hospitalized patients were studied for their haemagglutination ability, expression of lectins and hydrophobicity. Higher haemagglutination ability of clinical strains for human red blood cells was demonstrated, which could be an expression of their adaptation to the human ecosystem. Environmental strains had higher hydrophobicity, possibly related to adaptation to a low nutritive ecosystem. Expression of lectins was relatively low and comparable in both bacterial populations, but carbohydrate specificities were very different, possibly related to a different implication of these structures in the two ecosystems.

New binding assay and preparative trial of cell-surface lectin from Lactobacillus acidophilus group lactic acid bacteria

To select Lactobacillus acidophilus group bacteria as a probiotic yogurt starter, we designed a new screening method that measures the binding activity of surface layer protein to rat colonic mucin, which contains sugar chains similar to those in human colonic mucin. The B1 subgroup (Lactobacillus gasseri), which is the dominant strain in the human intestinal tract, showed the highest binding activity to rat colonic mucin among all the subgroups of L. acidophilus. The binding activity of the surface layer protein was also shown to be significantly reduced after periodate oxidation of the rat colonic mucin. This new screening method is useful for rapid selection of L. acidophilus strains that have high adhesion to the human intestinal tract. Lectin-like proteins that were bound to rat colonic mucin were isolated from the surface layer proteins with a rat colonic mucin-coated membrane and were analyzed by SDS-PAGE. A few main bands together with several minor bands were observed on the electrophoretograms obtained from the strains tested. It is possible that those lectin-like proteins contribute to adhesion of the bacterial cell to human colonic mucosa by binding specifically to carbohydrate portions.

Surface properties of bifidobacterial strains of human origin

The adherence of Bifidobacterium strains isolated from infant feces and commercial fermented dairy products to enterocyte-like cells was correlated with the autoagglutination and hemagglutination properties of these organisms. These results allowed us to define two groups: (i) cell-adherent bacteria showing hemagglutination and autoagglutination and (ii) non-cell-adherent, nonhemagglutinating, nonautoagglutinating bacteria. Glass adherence was shown to be nonspecific and was discarded as a criterion for selection of adherent cells. Hydrophobicity appeared to be necessary for adhesion to enterocyte-like cells and autoagglutination. Adhesive strains were highly hydrophobic, and the degree of adherence was slightly dependent on the surface potential. Cells autoagglutinated more when the electrostatic negative charges on the cell surface were shielded by a decrease in the pH from 7 to 2. However, in some strains negative charges at the cell surface were adjuvant to adhesion, thus suggesting that specific chemical interactions occurred. The present results provide a method for preliminary selection of bacteria potentially adherent to epithelial cells by means of autoagglutination.