Strain-Dependent Augmentation of Tight-Junction Barrier Function in Human Primary Epidermal Keratinocytes by Lactobacillus and Bifidobacterium Lysates

In this study, we investigated whether probiotic lysates can modify the tight-junction function of human primary keratinocytes. The keratinocytes were grown on cell culture inserts and treated with lysates from Bifidobacterium longum, Lactobacillus plantarum, Lactobacillus reuteri, Lactobacillus fermentum, or Lactobacillus rhamnosus GG. With the exception of L. fermentum (which decreased cell viability), all strains markedly enhanced tight-junction barrier function within 24 h, as assessed by measurements of transepithelial electrical resistance (TEER). However, B. longum and L. rhamnosus GG were the most efficacious, producing dose-dependent increases in resistance that were maintained for 4 days. These increases in TEER correlated with elevated expression of tight-junction protein components. Neutralization of Toll-like receptor 2 abolished both the increase in TEER and expression of tight-junction proteins induced by B. longum, but not L. rhamnosus GG. These data suggest that some bacterial strains increase tight-junction function via modulation of protein components but the different pathways involved may vary depending on the bacterial strain.     

Lactobacillus rhamnosus GG inhibits invasion of cultured human respiratory cells by prtF1-positive macrolide-resistant group A streptococci

Aims:  This study was designed to determine whether the probiotic strain Lactobacillus GG, which is extensively used in the treatment and prevention of intestinal disorders, is able to inhibit invasion of cultured human respiratory cells by macrolide-resistant group A streptococci (GAS) carrying the prtF1 gene, which encodes the fibronectin (Fn)-binding invasin F1.
Methods and Results:  Eight prtF1 -positive erythromycin-resistant GAS strains were used to infect A549 monolayers in competition and displacement assays with Lactobacillus GG. Live (L-LGG) and heat-killed (HK-LGG) lactobacilli and their spent culture supernatant (SCS) significantly reduced ( P  <   0·001) GAS invasion efficiency in both assays. No antibacterial activity of Lactobacillus GG against GAS was detected. Both L-LGG and HK-LGG and all prtF1 -positive GAS induced a strong agglutination reaction using Fn-coated particles.
Conclusions:  Lactobacillus GG exerts an antagonistic action against GAS by inhibiting cell invasion. Competitive binding of Lactobacillus GG and GAS to Fn might be involved in the inhibition process.
Significance and Impact of the Study:  The finding that Lactobacillus GG can prevent in vitro invasion of respiratory cells by GAS suggests new applications for this probiotic strain and warrants further studies of its capacity to prevent GAS throat infections.     

Functional characterization of a mucus-specific LPXTG surface adhesin from probiotic Lactobacillus rhamnosus GG

In spite of the wealth of clinical evidence supporting the health benefits of Lactobacillus rhamnosus GG in humans, there is still a lack of understanding of the molecular mechanisms behind its probiosis. Current knowledge suggests that the health-promoting effects of this probiotic strain might be partly dependent on its persistence in the intestine and adhesion to mucosal surfaces. Moreover, L. rhamnosus GG contains mucus-binding pili that might also explain the occupation of its ecological niche as a comparatively less stringent allochthonous intestine-dwelling bacterium. To uncover additional surface proteins involved in mucosal adhesion, we investigated the adherence properties of the only predicted protein (LGG_02337) in L. rhamnosus GG that exhibits homology with a known mucus-binding domain. We cloned a recombinant form of the gene for this putative mucus adhesin and established that the purified protein readily adheres to human intestinal mucus. We also showed that this mucus adhesin is visibly distributed throughout the cell surface and participates in the adhesive interaction between L. rhamnosus GG and mucus, although less prominently than the mucus-binding pili in this strain. Based on primary structural comparisons, we concluded that the current annotation of the LGG_02337 protein likely does not accurately reflect its predicted properties, and we propose that this mucus-specific adhesin be called the mucus-binding factor (MBF). Finally, we interpret our results to mean that L. rhamnosus GG MBF, as an active mucus-specific surface adhesin with a presumed ancillary involvement in pilus-mediated mucosal adhesion, plays a part in the adherent mechanisms during intestinal colonization by this probiotic.     

The effect of probiotic bacteria on the adhesion of pathogens to human intestinal mucus

Human intestinal glycoproteins extracted from faeces were used as a model for intestinal mucus to investigate adhesion of pathogenic Escherichia coli and Salmonella strains, and the effect of probiotics on this adhesion. S-fimbriated E. coli expressed relatively high adhesion in the mucus model, but the other tested pathogens adhered less effectively. Probiotic strains Lactobacillus GG and L. rhamnosus LC-705 as well as a L. rhamnosus isolated from human faeces were able to slightly reduce S-fimbria-mediated adhesion. Adhesion of S. typhimurium was significantly inhibited by probiotic L. johnsonii LJ1 and L. casei Shirota. Lactobacillus GG and L. rhamnosus (human isolate) increased the adhesion of S. typhimurium suggesting that the pathogen interacts with the probiotic.     

Persistence of Colonization of Human Colonic Mucosa by a Probiotic Strain, Lactobacillus rhamnosus GG, after Oral Consumption

Lactobacillus rhamnosus GG is one of the most thoroughly studied probiotic strains. Its advantages in the treatment of gastrointestinal disorders are well documented. The aim of the present study was to demonstrate with colonic biopsies the attachment of strain GG to human intestinal mucosae and the persistence of the attachment after discontinuation of GG administration. A whey drink fermented with strain GG was fed to human volunteers for 12 days. Fecal samples were collected before, during, and after consumption. L. rhamnosus GG-like colonies were detected in both fecal and colonic biopsy samples. Strain GG was identified by its characteristic colony morphology, a lactose fermentation test, and PCR. This study showed that strain GG was able to attach in vivo to colonic mucosae and, although the attachment was temporary, to remain for more than a week after discontinuation of GG administration. The results demonstrate that the study of fecal samples alone is not sufficient in evaluating colonization by a probiotic strain.     

Single bioreactor gastrointestinal tract simulator for study of survival of probiotic bacteria

The aim of the present study was to design an in vitro model system to evaluate the probiotic potential of food. A single bioreactor system-gastrointestinal tract simulator (GITS) was chosen for process simulation on account of its considerable simplicity compared to multi-vessel systems used in previous studies. The bioreactor was evaluated by studying the viability of four known probiotic bacteria (Lactobacillus acidophilus La-5, Lactobacillus johnsonii NCC 533, Lactobacillus casei strain Shirota, and Lactobacillus rhamnosus GG) as a function of their physiological state. L. acidophilus and L. johnsonii survived in GITS better when introduced at an early stationary or exponential phase compared to being previously stored for 2 weeks at 4 degrees C. These two species were more resistant to bile salts and survived better than L. casei and L. rhamnosus GG. The latter two species gave large losses (up to 6 log) in plate counts independent of growth state due to the bile. However, experiments with some commercial probiotic products containing Lb. GG bacteria showed much better survival compared with model food (modified deMan-Rogosa-Sharpe growth medium), thus demonstrating the influence of the food matrix on the viability of bacteria. The study demonstrated that GITS can be successfully used for evaluation of viability of probiotic bacteria and functionality of probiotic food.     

Molecular Cloning, Expression of minD Gene from Lactobacillus acidophilus VTCC-B-871 and Analyses to Identify Lactobacillus rhamnosus PN04 from Vietnam Hottuynia cordata Thunb.

The minD gene encoding an inhibitor cell division MinD homolog from Lactobacillus acidophilus VTCC-B-871 was cloned. We showed that there were 97 % homology between minD genes of L. acidophilus VTCC-B-871 and Lactobacillus rhamnosus GG and Lactobacillus rhamnosus Lc705. Based on the analysis of the DNA sequence data from the L. rhamnosus genome project and sequenced minD gene of L. acidophilus VTCC-B-871, a pair of primers was designed to identified the different minD genes from L. acidophilus ATCC 4356, L. rhamnosus ATCC 11443. Besides, the polymerase chain reaction product of minD gene was also obtained in L. rhamnosus PN04, a strain was isolated from Vietnamese Hottuynia cordata Thunb. In addition, we performed a phylogenetic analysis of the deduced amino acid sequence of MinD homologs from L. acidophilus VTCC-B-871 with the other strains and compared the predicted three-dimension structure of L. acidophilus VTCC-B-871 MinD with Escherichia coli MinD, there are similarity that showed evolution of these strains. The overexpression of L. acidophilus VTCC-B-871 MinD in E. coli led to cell filamentation in IPTG and morphology changes in different sugar stresses, interestingly. The present study is the first report characterizing the Lactobacilus MinD homolog that will be useful in probiotic field.     

Probability-based evaluation of peptide and protein identifications from tandem mass spectrometry and SEQUEST analysis: the human proteome

Large-scale protein identifications from highly complex protein mixtures have recently been achieved using multidimensional liquid chromatography coupled with tandem mass spectrometry (LC/LC-MS/MS) and subsequent database searching with algorithms such as SEQUEST. Here, we describe a probability-based evaluation of false positive rates associated with peptide identifications from three different human proteome samples. Peptides from human plasma, human mammary epithelial cell (HMEC) lysate, and human hepatocyte (Huh)-7.5 cell lysate were separated by strong cation exchange (SCX) chromatography coupled offline with reversed-phase capillary LC-MS/MS analyses. The MS/MS spectra were first analyzed by SEQUEST, searching independently against both normal and sequence-reversed human protein databases, and the false positive rates of peptide identifications for the three proteome samples were then analyzed and compared. The observed false positive rates of peptide identifications for human plasma were significantly higher than those for the human cell lines when identical filtering criteria were used, suggesting that the false positive rates are significantly dependent on sample characteristics, particularly the number of proteins found within the detectable dynamic range. Two new sets of filtering criteria are proposed for human plasma and human cell lines, respectively, to provide an overall confidence of >95% for peptide identifications. The new criteria were compared, using a normalized elution time (NET) criterion (Petritis et al. Anal. Chem. 2003, 75, 1039-1048), with previously published criteria (Washburn et al. Nat. Biotechnol. 2001, 19, 242-247). The results demonstrate that the present criteria provide significantly higher levels of confidence for peptide identifications from mammalian proteomes without greatly decreasing the number of identifications.     

Epithelial Adhesion Mediated by Pilin SpaC Is Required for Lactobacillus rhamnosus GG-Induced Cellular Responses

Lactobacillus rhamnosus GG is a widely used probiotic, and the strain''s salutary effects on the intestine have been extensively documented. We previously reported that strain GG can modulate inflammatory signaling, as well as epithelial migration and proliferation, by activating NADPH oxidase 1-catalyzed generation of reactive oxygen species (ROS). However, how strain GG induces these responses is unknown. Here, we report that strain GG''s probiotic benefits are dependent on the bacterial-epithelial interaction mediated by the SpaC pilin subunit. By comparing strain GG to an isogenic mutant that lacks SpaC (strain GGΩspaC), we establish that SpaC is necessary for strain GG to adhere to gut mucosa, that SpaC contributes to strain GG-induced epithelial generation of ROS, and that SpaC plays a role in strain GG''s capacity to stimulate extracellular signal-regulated kinase/mitogen-activated protein kinase (ERK/MAPK) signaling in enterocytes. In addition, we show that SpaC is required for strain GG-mediated stimulation of cell proliferation and protection against radiologically inflicted intestinal injury. The identification of a critical surface protein required for strain GG to mediate its probiotic influence advances our understanding of the molecular basis for the symbiotic relationship between some commensal bacteria of the gut lumen and enterocytes. Further insights into this relationship are critical for the development of novel approaches to treat intestinal diseases.     

The Lactobacillus plantarum strain ACA-DC287 isolated from a Greek cheese demonstrates antagonistic activity in vitro and in vivo against Salmonella enterica serovar Typhimurium

AIMS: The purpose of this study was to investigate the antibacterial activity of the Xynotyri cheese isolate Lactobacillus plantarum ACA-DC287 using a set of in vitro and in vivo assays. METHODS AND RESULTS: The co-culture of L. plantarum strain ACA-DC287 and Salmonella enterica serovar Typhimurium strain SL1344 results in the killing of the pathogen. The killing activity was produced mainly by non-lactic acid molecule(s) that were present in the cell-free culture supernatant of the L. plantarum strain ACA-DC287. The culture of the L. plantarum strain ACA-DC287 inhibited the penetration of S. typhimurium SL1344 into cultured human enterocyte-like Caco-2/TC7 cells. In conventional mice infected with S. typhimurium SL1344, the intake of L. plantarum strain ACA-DC287 results in a decrease in the levels of Salmonella associated with intestinal tissues or those present in the intestinal contents. In germ-free mice, the L. plantarum strain ACA-DC287 colonized the gastrointestinal tract. CONCLUSIONS: The L. plantarum strain ACA-DC287 strain exerts anti-Salmonella activity similar that of the established probiotic strains Lactobacillus rhamnosus GG, Lactobacillus casei Shirota YIT9029 and Lactobacillus johnsonii La1. SIGNIFICANCE AND IMPACT OF THE STUDY: The observation that a selected cheese Lactobacillus strain exerted antibacterial activity that was similar to those of probiotic Lactobacillus strains, is of interest for the use of this strain as an adjunct strain for the production of health-giving cheeses.     

Improving sensitivity in proteome studies by analysis of false discovery rates for multiple search engines

LC‐MS experiments can generate large quantities of data, for which a variety of database search engines are available to make peptide and protein identifications. Decoy databases are becoming widely used to place statistical confidence in result sets, allowing the false discovery rate (FDR) to be estimated. Different search engines produce different identification sets so employing more than one search engine could result in an increased number of peptides (and proteins) being identified, if an appropriate mechanism for combining data can be defined. We have developed a search engine independent score, based on FDR, which allows peptide identifications from different search engines to be combined, called the FDR Score. The results demonstrate that the observed FDR is significantly different when analysing the set of identifications made by all three search engines, by each pair of search engines or by a single search engine. Our algorithm assigns identifications to groups according to the set of search engines that have made the identification, and re‐assigns the score (combined FDR Score). The combined FDR Score can differentiate between correct and incorrect peptide identifications with high accuracy, allowing on average 35% more peptide identifications to be made at a fixed FDR than using a single search engine.     

Global proteome discovery using an online three-dimensional LC-MS/MS

We have developed a proteomics technology featuring on-line three-dimensional liquid chromatography coupled to tandem mass spectrometry (3D LC-MS/MS). Using 3D LC-MS/MS, the yeast-soluble, urea-solubilized peripheral membrane and SDS-solubilized membrane protein samples collectively yielded 3019 unique yeast protein identifications with an average of 5.5 peptides per protein from the 6300-gene Saccharomyces Genome Database searched with SEQUEST. A single run of the urea-solubilized sample yielded 2255 unique protein identifications, suggesting high peak capacity and resolving power of 3D LC-MS/MS. After precipitation of SDS from the digested membrane protein sample, 3D LC-MS/MS allowed the analysis of membrane proteins. Among 1221 proteins containing two or more predicted transmembrane domains, 495 such proteins were identified. The improved yeast proteome data allowed the mapping of many metabolic pathways and functional categories. The 3D LC-MS/MS technology provides a suitable tool for global proteome discovery.     

Flow cytometric testing of green fluorescent protein-tagged Lactobacillus rhamnosus GG for response to defensins

Lactobacillus rhamnosus GG is of general interest as a probiotic. Although L. rhamnosus GG is often used in clinical trials, there are few genetic tools to further determine its mode of action or to develop it as a vehicle for heterologous gene expression in therapy. Therefore, we developed a reproducible, efficient electroporation procedure for L. rhamnosus GG. The best transformation efficiency obtained was 10(4) transformants per microg of DNA. We validated this protocol by tagging L. rhamnosus GG with green fluorescent protein (GFP) using the nisin-controlled expression (NICE) system. Parameters for overexpression were optimized, which allowed expression of gfp in L. rhamnosus GG upon induction with nisin. The GFP+ strain can be used to monitor the survival and behavior of L. rhamnosus GG in vivo. Moreover, implementation of the NICE system as a gene expression switch in L. rhamnosus GG opens up possibilities for improving and expanding the performance of this strain. The GFP-labeled strain was used to demonstrate that L. rhamnosus GG is sensitive to human beta-defensin-2 but not to human beta-defensin-1.     

Study of adhesion and survival of lactobacilli and bifidobacteria on table olives with the aim of formulating a new probiotic food

With the aim of developing new functional foods, a traditional product, the table olive, was used as a vehicle for incorporating probiotic bacterial species. Survival on table olives of Lactobacillus rhamnosus (three strains), Lactobacillus paracasei (two strains), Bifidobacterium bifidum (one strain), and Bifidobacterium longum (one strain) at room temperature was investigated. The results obtained using a selected olive sample demonstrated that bifidobacteria and one strain of L. rhamnosus (Lactobacillus GG) showed a good survival rate, with a recovery of about 10(6) CFU g(-1) after 30 days. The Lactobacillus GG population remained unvaried until the end of the experiment, while a slight decline (to about 10(5) CFU g(-1)) was observed for bifidobacteria. High viability, with more than 10(7) CFU g(-1), was observed throughout the 3-month experiment for L. paracasei IMPC2.1. This strain, selected for its potential probiotic characteristics and for its lengthy survival on olives, was used to validate table olives as a carrier for transporting bacterial cells into the human gastrointestinal tract. L. paracasei IMPC2.1 was recovered from fecal samples in four out of five volunteers fed 10 to 15 olives per day carrying about 10(9) to 10(10) viable cells for 10 days.     

Taxonomic and strain-specific identification of the probiotic strain Lactobacillus rhamnosus 35 within the Lactobacillus casei group

Lactobacilli are lactic acid bacteria that are widespread in the environment, including the human diet and gastrointestinal tract. Some Lactobacillus strains are regarded as probiotics because they exhibit beneficial health effects on their host. In this study, the long-used probiotic strain Lactobacillus rhamnosus 35 was characterized at a molecular level and compared with seven reference strains from the Lactobacillus casei group. Analysis of rrn operon sequences confirmed that L. rhamnosus 35 indeed belongs to the L. rhamnosus species, and both temporal temperature gradient gel electrophoresis and ribotyping showed that it is closer to the probiotic strain L. rhamnosus ATCC 53103 (also known as L. rhamnosus GG) than to the species type strain. In addition, L. casei ATCC 334 gathered in a coherent cluster with L. paracasei type strains, unlike L. casei ATCC 393, which was closer to L. zeae; this is evidence of the lack of relatedness between the two L. casei strains. Further characterization of the eight strains by pulsed-field gel electrophoresis repetitive DNA element-based PCR identified distinct patterns for each strain, whereas two isolates of L. rhamnosus 35 sampled 40 years apart could not be distinguished. By subtractive hybridization using the L. rhamnosus GG genome as a driver, we were able to isolate five L. rhamnosus 35-specific sequences, including two phage-related ones. The primer pairs designed to amplify these five regions allowed us to develop rapid and highly specific PCR-based identification methods for the probiotic strain L. rhamnosus 35.     

Comparison of alternative analytical techniques for the characterisation of the human serum proteome in HUPO Plasma Proteome Project

Based on the same HUPO reference specimen (C1-serum) with the six proteins of highest abundance depleted by immunoaffinity chromatography, we have compared five proteomics approaches, which were (1) intact protein fractionation by anion-exchange chromatography followed by 2-DE-MALDI-TOF-MS/MS for protein identification (2-DE strategy); (2) intact protein fractionation by 2-D HPLC followed by tryptic digestion of each fraction and microcapillary RP-HPLC/microESI-MS/MS identification (protein 2-D HPLC fractionation strategy); (3) protein digestion followed by automated online microcapillary 2-D HPLC (strong cation-exchange chromatography (SCX)-RPC) with IT microESI-MS/MS; (online shotgun strategy); (4) same as (3) with the SCX step performed offline (offline shotgun strategy) and (5) same as (4) with the SCX fractions reanalysed by optimised nanoRP-HPLC-nanoESI-MS/MS (offline shotgun-nanospray strategy). All five approaches yielded complementary sets of protein identifications. The total number of unique proteins identified by each of these five approaches was (1) 78, (2) 179, (3) 131, (4) 224 and (5) 330 respectively. In all, 560 unique proteins were identified. One hundred and sixty-five proteins were identified through two or more peptides, which could be considered a high-confidence identification. Only 37 proteins were identified by all five approaches. The 2-DE approach yielded more information on the pI-altered isoforms of some serum proteins and the relative abundance of identified proteins. The protein prefractionation strategy slightly improved the capacity to detect proteins of lower abundance. Optimising the separation at the peptide level and improving the detection sensitivity of ESI-MS/MS were more effective than fractionation of intact proteins in increasing the total number of proteins identified. Overall, electrophoresis and chromatography, coupled respectively with MALDI-TOF/TOF-MS and ESI-MS/MS, identified complementary sets of serum proteins.     

Whole-genome shotgun sequencing of Lactobacillus rhamnosus MTCC 5462, a strain with probiotic potential

Lactobacillus rhamnosus MTCC 5462 was isolated from infant gastrointestinal flora. The strain exhibited an ability to reduce cholesterol and stimulate immunity. The strain has exhibited positive results in alleviating gastrointestinal discomfort and good potential as a probiotic. We sequenced the whole genome of the strain and compared it to the published genome sequence of Lactobacillus rhamnosus GG (ATCC 53103).