A mucus adhesion promoting protein, MapA, mediates the adhesion of Lactobacillus reuteri to Caco-2 human intestinal epithelial cells

Lactobacillus reuteri is one of the dominant lactobacilli found in the gastrointestinal tract of various animals. A surface protein of L. reuteri 104R, mucus adhesion promoting protein (MapA), is considered to be an adhesion factor of this strain. We investigated the relation between MapA and adhesion of L. reuteri to human intestinal (Caco-2) cells. Quantitative analysis of the adhesion of L. reuteri strains to Caco-2 cells showed that various L. reuteri strains bind not only to mucus but also to intestinal epithelial cells. In addition, purified MapA bound to Caco-2 cells, and this binding inhibited the adhesion of L. reuteri in a concentration-dependent manner. Based on these observations, the adhesion of L. reuteri appears due to the binding of MapA to receptor-like molecules on Caco-2 cells. Further, far-western analysis indicated the existence of multiple receptor-like molecules in Caco-2 cells.     

Adhesion of Vancomycin-Resistant Enterococcus to Human Intestinal Mucus

The intestinal mucus layer provides a potential niche for colonization by vancomycin-resistant Enterococcus faecium (VREF). We therefore examined the ability of six VREF strains to adhere to human intestinal mucus and determined binding kinetics. Four of six (67%) VREF strains demonstrated significant adhesion to immobilized intestinal mucus compared with a Salmonella typhimurium–negative control strain, but the level of adherence was low compared with Lactobacillus rhamnosus GG. Binding kinetics studies demonstrated that the maximum number of these four VREF strains that could adhere to a unit surface area of immobilized mucus was similar to or higher than the maximum number of L. rhamnosus GG that could adhere; however, L. rhamnosus GG demonstrated 20- to 130-times higher affinity than the VREF strains. These results demonstrate that VREF strains may adhere to human intestinal mucus and suggest that L. rhamnosus GG might be able to displace VREF strains.     

Piliation of Lactobacillus rhamnosus GG Promotes Adhesion,Phagocytosis, and Cytokine Modulation in Macrophages

Recently, spaCBA-encoded pili on the cell surface of Lactobacillus rhamnosus GG were identified to be key molecules for binding to human intestinal mucus and Caco-2 intestinal epithelial cells. Here, we investigated the role of the SpaCBA pilus of L. rhamnosus GG in the interaction with macrophages in vitro by comparing the wild type with surface mutants. Our results show that SpaCBA pili play a significant role in the capacity for adhesion to macrophages and also promote bacterial uptake by these phagocytic cells. Interestingly, our data suggest that SpaCBA pili also mediate anti-inflammatory effects by induction of interleukin-10 (IL-10) mRNA and reduction of interleukin-6 (IL-6) mRNA in a murine RAW 264.7 macrophage cell line. These pili appear to mediate these effects indirectly by promoting close contact with the macrophages, facilitating the exertion of anti-inflammatory effects by other surface molecules via yet unknown mechanisms. Blockage of complement receptor 3 (CR3), previously identified to be a receptor for streptococcal pili, significantly decreased the uptake of pilus-expressing strains in RAW 264.7 cells, while the expression of IL-10 and IL-6 mRNA by these macrophages was not affected by this blocking. On the other hand, blockage of Toll-like receptor 2 (TLR2) significantly reduced the expression of IL-6 mRNA irrespective of the presence of pili.     

Structural and molecular insights into novel surface‐exposed mucus adhesins from Lactobacillus reuteri human strains

The mucus layer covering the gastrointestinal tract is the first point of contact of the intestinal microbiota with the host. Cell surface macromolecules are critical for adherence of commensal bacteria to mucus but structural information is scarce. Here we report the first molecular and structural characterization of a novel cell‐surface protein, Lar_0958 from Lactobacillus reuteri JCM 1112^T, mediating adhesion of L. reuteri human strains to mucus. Lar_0958 is a modular protein of 133 kDa containing six repeat domains, an N‐terminal signal sequence and a C‐terminal anchoring motif (LPXTG). Lar_0958 homologues are expressed on the cell‐surface of L. reuteri human strains, as shown by flow‐cytometry and immunogold microscopy. Adhesion of human L. reuteri strains to mucus in vitro was significantly reduced in the presence of an anti‐Lar_0958 antibody and Lar_0958 contribution to adhesion was further confirmed using a L. reuteri ATCC PTA 6475 lar_0958 KO mutant (6475‐KO). The X‐ray crystal structure of a single Lar_0958 repeat, determined at 1.5 Å resolution, revealed a divergent immunoglobulin (Ig)‐like β‐sandwich fold, sharing structural homology with the Ig‐like inter‐repeat domain of internalins of the food borne pathogen Listeria monocytogenes. These findings provide unique structural insights into cell‐surface protein repeats involved in adhesion of Gram‐positive bacteria to the intestine.     

Adhesion of the probiotic strains <Emphasis Type="Italic">Enterococcus mundtii</Emphasis> ST4SA and <Emphasis Type="Italic">Lactobacillus plantarum</Emphasis> 423 to Caco-2 cells under conditions simulating the intestinal tract,and in the presence of antibiotics and anti-inflammatory medicaments

Adhesion of Enterococcus mundtii ST4SA and Lactobacillus plantarum 423 to Caco-2 (human carcinoma epithelial) cells was visualized by fluorescent staining. Both strains showed good adhesion compared to L. casei MB1, L. casei Shirota, L. johnsonii La1 and L. rhamnosus GG. No correlation was found between hydrophobicity, aggregation and adhesion to Caco-2 cells. Presence of antibiotics and anti-inflammatory medicaments reduced adhesion of bacterial strains to Caco-2 cells. Proteins sensitive to pepsin, trypsin and pronase are involved in the adhesion of E. mundtii ST4SA and L. plantarum 423 to Caco-2 cells. Adhesion of Listeria monocytogenes ScottA to Caco-2 cells was not prevented by E. mundtii ST4SA and L. plantarum 423. Cell-free culture supernatants of strains ST4SA and 423, containing the antimicrobial peptides plantaricin 423 and peptide ST4SA, prevented the invasion of L. monocytogenes ScottA into Caco-2 cells.     

Identification and characterization of adhesive factors of Clostridium difficile involved in adhesion to human colonic enterocyte-like Caco-2 and mucus-secreting HT29 cells in culture

Experiments reported in this communication showed that the highly toxinogenic Cd 79685, Cd 4784, and Wilkins Clostridium difficile strains and the moderately toxinogenic FD strain grown in the presence of blood adhere to polarized monolayers of two cultured human intestinal cell lines: the human colonic epithelial Caco-2 cells and the human mucus-secreting HT29-MTX cells. Scanning electron microscopy revealed that the bacteria interacted with well-defined apical microvilli of differentiated Caco-2 cells and that the bacteria strongly bind to the mucus layer that entirely covers the surface of the HT29-MTX cells. The binding of C. difficile to Caco-2 cells developed in parallel with the differentiation features of the Caco-2 cells, suggesting that the protein(s) which constitute C. difficile-binding sites are differentiation-related brush border protein(s). To better define this interaction, we tentatively characterized the mechanism(s) of adhesion of C. difficile with adherence assays. It was shown that heating of C. difficile grown in the presence of blood enhanced the bacterial interaction with the brush border of the enterocyte-like Caco-2 cells and the human mucus-secreting HT29-MTX cells. A labile surface-associated component was involved in C. difficile adhesion since washes of C. difficile grown in the presence of blood without heat shock decreased adhesion. After heating, washes of C. difficile grown in the presence of blood did not modify adhesion. Analysis of surface-associated proteins of C. difficile subjected to different culture conditions was con-ducted. After growth of C. difficile Cd 79685, Cd 4784, FD and Wilkins strains in the presence of blood and heating, two predominant SDS-extractable proteins with molecular masses of 12 and 27 kDa were observed and two other proteins with masses of 48 and 31 kDa disappeared. Direct involvement of the 12 and 27 kDa surface-associated proteins in the adhe-sion of C. difficile strains was demonstrated by using rat polycolonal antibodies pAb 12 and pAb 27 directed against the 12 and 27kDa proteins. Indeed, adhesion to Caco-2 cell monoiayers of C. difficiie strains grown in the presence of blood, without or with heat-shock, was blocked. Taken together, our results suggest that C. difficiie may utilize blood components as adhesins to adhere to human intestinal cultured cells.     

Probiotic Strains and Their Combination Inhibit <Emphasis Type="Italic">In Vitro</Emphasis> Adhesion of Pathogens to Pig Intestinal Mucosa

The aim of this study was to investigate in vitro the protective effect of commercial probiotic strains (Bifidobacterium lactis Bb12 and Lactobacillus rhamnosus LGG) alone and in combination on the adhesion of pathogenic strains as Salmonella, Clostridium, and Escherichia coli to pig intestinal mucus obtained from different intestinal regions. In combination, probiotic strains enhanced each other’s adhesion, mainly in large intestinal mucus. Treatment of intestinal mucus with Bb12 and LGG, alone or in combination, significantly reduced (P < 0.05) the adhesion of the tested pathogens. The ability to inhibit pathogen adhesion appears to depend on the specific probiotics and pathogens and on the mucosal site. B. lactis Bb12 and L. rhamnosus LGG in combination revealed a better ability to inhibit adhesion of all pathogens tested to pig intestinal mucus than probiotic strains. Probiotic combinations could be useful for counteracting disease-associated aberrations in intestinal microbiota. Specific protective probiotics could be selected for particular pig pathogens. Probiotic strains from human origin and intended for human use also adhere to pig intestinal mucus and are able to displace and inhibit pathogens.     

Adhesion of human bifidobacterial strains to cultured human intestinal epithelial cells and inhibition of enteropathogen-cell interactions.

Thirteen human bifidobacterial strains were tested for their abilities to adhere to human enterocyte-like Caco-2 cells in culture. The adhering strains were also tested for binding to the mucus produced by the human mucus-secreting HT29-MTX cell line in culture. A high level of calcium-independent adherence was observed for Bifidobacterium breve 4, for Bifidobacterium infantis 1, and for three fresh human isolates from adults. As observed by scanning electron microscopy, adhesion occurs to the apical brush border of the enterocytic Caco-2 cells and to the mucus secreted by the HT29-MTX mucus-secreting cells. The bacteria interacted with the well-defined apical microvilli of Caco-2 cells without cell damage. The adhesion to Caco-2 cells of bifidobacteria did not require calcium and was mediated by a proteinaceous adhesion-promoting factor which was present both in the bacterial whole cells and in the spent supernatant of bifidobacterium culture. This adhesion-promoting factor appeared species specific, as are the adhesion-promoting factors of lactobacilli. We investigated the inhibitory effect of adhering human bifidobacterial strains against intestinal cell monolayer colonization by a variety of diarrheagenic bacteria. B. breve 4, B. infantis 1, and fresh human isolates were shown to inhibit cell association of enterotoxigenic, enteropathogenic, diffusely adhering Escherichia coli and Salmonella typhimurium strains to enterocytic Caco-2 cells in a concentration-dependent manner. Moreover, B. breve 4 and B. infantis 1 strains inhibited, dose dependently, Caco-2 cell invasion by enteropathogenic E. coli, Yersinia pseudotuberculosis, and S. typhimurium strains.     

Influence of Temperature and Growth Phase on Expression of a 104-Kilodalton Listeria Adhesion Protein in Listeria monocytogenes

Interaction of Listeria monocytogenes with mammalian intestinal cells is believed to be an important first step in Listeria pathogenesis. Transposon (Tn916) mutagenesis provided strong evidence that a 104-kDa surface protein, designated the Listeria adhesion protein (LAP), was involved in adherence of L. monocytogenes to a human enterocyte-like Caco-2 cell line (V. Pandiripally, D. Westbrook, G. Sunki, and A. Bhunia, J. Med. Microbiol. 48:117–124, 1999). In this study, expression of LAP in L. monocytogenes at various growth temperatures (25, 37, and 42°C) and in various growth phases was determined by performing an enzyme-linked immunoassay (ELISA) and Western blotting with a specific monoclonal antibody (monoclonal antibody H7). The ELISA and Western blot results indicated that there was a significant increase in LAP expression over time only at 37 and 42°C and that the level of LAP expression was low during the exponential phase and high during the stationary phase. In contrast, there were not significant differences in LAP expression between the exponential and stationary phases at 25°C. Examination of the adhesion of L. monocytogenes cells from exponential-phase (12-h) or stationary-phase (24-h) cultures grown at 37°C to Caco-2 cells revealed that there were not significant differences in adhesion. Although expression of L. monocytogenes LAP was different at different growth temperatures and in different growth phases, enhanced expression did not result in increased adhesion, possibly because only a few LAP molecules were sufficient to initiate binding to Caco-2 cells.     

Implication of an Outer Surface Lipoprotein in Adhesion of Bifidobacterium bifidum to Caco-2 Cells

We found that the human intestinal isolate Bifidobacterium bifidum MIMBb75 strongly adhered to Caco-2 cells. Proteinase K and lithium chloride treatments showed that proteins play a key role in MIMBb75 adhesion to Caco-2 cells. By studying the cell wall-associated proteins, we identified a surface protein, which we labeled BopA. We purified the protein chromatographically and found that it functioned as an adhesion promoter on Caco-2 cells. In silico analysis of the gene coding for this protein and globomycin experiments showed that BopA is a cysteine-anchored lipoprotein expressed as a precursor polypeptide. A database search indicated that BopA appears to function biologically as an oligopeptide/tripeptide-solute-binding protein in the ABC transport system. We discovered a protein corresponding to BopA and its gene in eight other highly adherent B. bifidum strains. Finally, we found that B. bifidum MIMBb75 and BopA affected the production of interleukin-8 in Caco-2 epithelial cells. BopA is the first protein described to date to be directly involved in the adhesion of bifidobacteria to Caco-2 cells and to show immunomodulatory activity.     

Antagonistic Activity of <Emphasis Type="Italic">Lactobacillus acidophilus</Emphasis> ATCC 4356 on the Growth and Adhesion/Invasion Characteristics of Human <Emphasis Type="Italic">Campylobacter jejuni</Emphasis>

The aim of this research was to determine the potential probiotic activity of Lactobacillus acidophilus ATCC 4356 against several human Campylobacter jejuni isolates. The ability to inhibit the pathogen’s growth was evaluated by co-culture experiments as well as by antimicrobial assays with cell-free culture supernatant (CFCS), while interference with adhesion/invasion to intestinal Caco-2 cells was studied by exclusion, competition, and displacement tests. In the co-culture experiments L. acidophilus ATCC 4356 strain reduced the growth of C. jejuni with variable percentages of inhibition related to the contact time. The CFCS showed inhibitory activity against C. jejuni strains, stability to low pH, and thermal treatment and sensitivity to proteinase K and trypsin. L. acidophilus ATCC 4356 was able to reduce the adhesion and invasion to Caco-2 cells by most of the human C. jejuni strains. Displacement and exclusion mechanisms seem to be the preferred modalities, which caused a significant reduction of adhesion/invasion of pathogens to intestinal cells. The observed inhibitory properties of L. acidophilus ATCC 4356 on growth ability and on cells adhesion/invasion of C. jejuni may offer potential use of this strain for the management of Campylobacter infections.     

Adhesion of probiotic lactobacilli to chick intestinal mucus

In the present work, interactions between three Lactobacillus strains (Lactobacillus fermentum CRL1015, Lactobacillus animalis CRL1014, and Lactobacillus fermentum CRL1016) and chicken small intestinal mucus were determined. Three lactobacilli isolated from chicken and selected by their potentially probiotic properties were able to grow in mucus preparations. Three peaks from gel filtration chromatography of intestinal mucus were obtained. The adhesion to three mucus fractions (I, II, and III), especially fraction III, was higher (P < 0.01) in L. fermentum CRL1015 than L. animalis CRL1014. Pretreatment of this fraction with proteases and metaperiodate showed lower (P < 0.01) adhesion values than that of the control, suggesting that a glycoprotein from the mucus acts as a receptor for L. fermentum CRL1015. Highest adhesion values were obtained at pH 7 and 42 degrees C, and neither the removal of divalent cations with ethylenediaminetetraacetic acid (EDTA) nor the addition of calcium produced significant variation from the adhesion values of the control (P > 0.01). This adhesion was only inhibited by N-acetyl-glucosamine. Salmonella pullorum and Salmonella gallinarum showed high (P < 0.01) values of adhesion to chick intestinal mucus. The results obtained from assays of the inhibition of adherence of Salmonella spp. to mucus, immobilized in polystyrene tissue culture wells, indicated that the pathogen adhesion was not reduced by lactobacilli (P > 0.05) or their spent culture supernatants (P > 0.05), suggesting that these strains did not interfere with the binding sites for Salmonella spp. adhesion to the small intestinal mucus.     

Quantitative Approach in the Study of Adhesion of Lactic Acid Bacteria to Intestinal Cells and Their Competition with Enterobacteria

To describe the phenomena of bacterial adhesion to intestinal cells and the competition for adhesion between bacteria, mathematical equations based on a simple dissociation process involving a finite number of bacterial receptors on intestinal cell surface were developed. The equations allow the estimation of the maximum number of Lactobacillus sp. and Escherichia coli cells that can adhere to Caco-2 cells and intestinal mucus; they also characterize the affinity of the bacteria to Caco-2 cells and intestinal and fecal mucus and the theoretical adhesion ratio of two bacteria present in a mixed suspension. The competition for adhesion between Lactobacillus rhamnosus GG and E. coli TG1 appeared to follow the proposed kinetics, whereas the competition between Lactobacillus casei Shirota and E. coli TG1 may involve multiple adhesion sites or a soluble factor in the culture medium of the former. The displacement of the adhered Lactobacillus by E. coli TG1 seemed to be a rapid process, whereas the displacement of E. coli TG1 by the Lactobacillus took more than an hour.     

Aciduric Strains of <Emphasis Type="Italic">Lactobacillus reuteri</Emphasis> and <Emphasis Type="Italic">Lactobacillus rhamnosus</Emphasis>, Isolated from Human Feces,Have Strong Adhesion and Aggregation Properties

Human feces were streaked onto MRS Agar adjusted to pH 2.5, 3.0, and 6.4, respectively, and medium supplemented with 1.0% (w/v) bile salts. Two aciduric strains, identified as Lactobacillus reuteri HFI-LD5 and Lactobacillus rhamnosus HFI-K2 (based on 16S rDNA and recA sequences), were non-hemolytic and did not hydrolyze mucin. The surface of Lactobacillus reuteri HFI-LD5 cells has a weak negative charge, whereas Lactobacillus rhamnosus HFI-K2 has acidic and basic properties, and produces exopolysaccharides (EPS). None of the strains produce bacteriocins. Both strains are resistant to several antibiotics, including sulfamethoxazole-trimethoprim and sulphonamides. The ability of Lactobacillus reuteri HFI-LD5 and Lactobacillus rhamnosus HFI-K2 to grow at pH 2.5 suggests that they will survive passage through the stomach. EPS production may assist in binding to intestinal mucus, especially in the small intestinal tract, protect epithelial cells, and stimulate the immune system. Lactobacillus reuteri HFI-LD5 and Lactobacillus rhamnosus HFI-K2 may be used as probiotics, especially in the treatment of small intestinal bacterial overgrowth (SIBO).     

Reduction of Sulfide, Ammonia Compounds, and Adhesion Properties of Lactobacillus casei Strain KE99 In Vitro

The ability of Lactobacillus casei strain KE99 to reduce sulfide, ammonia, and to adhere to bio-surfaces was characterized and compared with three lactobacillus reference strains. Sulfide reduction by strain KE99 in MRS broth increased exponentially after 10-h growth and reached a maximum (>300 ppm reduction) within 48 h. KE99 demonstrated a maximum reduction of sulfide under anaerobic (341 ppm) growth conditions at pH 6.0-8.0 range. Maximum anaerobic reduction of sulfide was demonstrated by L. casei 393 at pH 7.0 (272 ppm); L. rhamnosus at pH 8.0 (277 ppm); and L. reuteri at pH 7.0 (244 ppm). KE99 reduced sulfide more (p < 0.0001) in MRS broth spiked with Na₂S (374 ppm) than (NH₄)₂S (340 ppm) salts. Ammonia reduction by strain KE99 and the three lactobacillus reference strains in MRS broth was low. Ammonia reduction reached a maximum within 36 h and remained unchanged over extended incubations of 48 h to 72 h or further. KE99 reduced ammonium sulfate (37 ppm) more readily than the nitrate (31 ppm), hypophosphate (29 ppm), or chloride (20 ppm) salts of ammonia. KE99 and the three reference strains of lactobacilli demonstrated avid binding to Bio-coat™ (Cn type-I, Cn type-IV, laminin, fibronectin), Matrigel™, and Caco-2 cell monolayers in vitro. The number of lactobacilli binding to Caco-2 was estimated at 74/cell with strain KE99, which was significantly higher compared with 40/cell (p < 0.0001), 26/cell (0.0001), and 64/cell (p < 0.002) with L. casei 393, L. reuteri, and L. rhamnosus, respectively. The interaction of KE99 to immobilized Cn type-I was saturable and reached an equilibrium within 1 h at room temperature. KE99 binding to Cn type-I occurred at a wide pH range and was biphasic with maximum binding at pH 5.5 and 7.5. Inhibition and binding-displacement experiments with different salts and sugars suggested that the KE99 binding to immobilized Cn type-I may involve a combination of electrostatic and lectin-type interactions. KE99 effectively detached the Cn-adherent E. coli O157:H7 in the range of 55% (ATCC43895) to 76% (ATCC43894). The binding-displacement values for L. casei 393, L. reuteri and L. rhamnosus to detach Cn-adherent E. coli O157:H7 (ATCC43894) were 66 ± 4%, 59 ± 2%, and 64 ± 2%, respectively. Also, a reconstituted solution of the freeze-dried KE99 preparation effectively detached the Cn-adherent E. coli O157:H7 in a dose-dependent manner that reached a binding-displacement equilibrium of 85% at a 1% wt/vol KE99 concentration. Received: 25 May 2001 / Accepted: 2 July 2001     

Inhibitory potential of lactobacilli against <Emphasis Type="Italic">Escherichia coli</Emphasis> internalization by HT 29 cells

A quantitative fluorescent in situ hybridization method was employed to evaluate the competitive inhibitory effect of three Lactobacillus strains (Lactobacillus reuteri, Lactobacillus gasseri, and Lactobacillus plantarum) against Escherichia coli internalization in a model system of HT 29 cells. Furthermore, aggregation and adhesion abilities of the Lactobacillus strains were examined. All lactobacilli were able to attach to the HT 29 cells and aggregate with pathogens; however, the adhesion and aggregation degree was strain-dependent. L. reuteri possessed a high capacity of adhesion (6.80 ± 0.63; log CFU ± SEM per well), whereas lower capacities were expressed by L. gasseri (4.52 ± 0.55) and L. plantarum (4.90 ± 0.98). Additionally, L. reuteri showed the rapid or normal ability to aggregate with selected E. coli in comparison with remaining two lactobacilli, which showed only slow or negative aggregative reaction. Internalization of E. coli into the cell lines was markedly suppressed by L. reuteri, while L. gasseri and L. plantarum caused only a minimum anti-invasion effect. The fact that L. reuteri in our experiments showed an outstanding potential for adhering to the colon epithelial cell line, compared with the rest strains, suggested that one of the possible mechanisms of preventing pathogen adhesion and invasion is simple competitions at certain receptors and capability to block receptor binding sites, or that an avid interaction between L. reuteri and the host cell might be modulating intracellular events responsible for the E. coli internalization. Moreover, L. reuteri exhibited a strong ability to aggregate with E. coli, which could be another limiting factor of pathogen invasion.     

Comparison of the Caco-2, HT-29 and the mucus-secreting HT29-MTX intestinal cell models to investigate Salmonella adhesion and invasion

Human intestinal cell models are widely used to study host-enteric pathogen interactions, with different cell lines exhibiting specific characteristics and functions in the gut epithelium. In particular, the presence of mucus may play an important role in adhesion and invasion of pathogens. The aim of this study was to evaluate the suitability of the mucus-secreting HT29-MTX intestinal epithelial cell model to test adhesion and invasion of Salmonella strains and compare with data obtained with the more commonly used Caco-2 and HT-29 models. Adhesion of Salmonella to HT29-MTX cell model was significantly higher, likely due to high adhesiveness to mucins present in the native human mucus layer covering the whole cell surface, compared to the non- and low-mucus producing Caco-2 and HT-29 cell models, respectively. In addition, invasion percentages of some clinical Salmonella strains to HT29-MTX cultures were remarkably higher than to Caco-2 and HT-29 cells suggesting that these Salmonellae have subverted the mucus to enhance pathogenicity. The transepithelial electrical resistances of the infected HT29-MTX cell model decreased broadly and were highly correlated with invasion ability of the strain. Staining of S. Typhimurium-infected cell epithelium confirmed the higher invasion by Salmonella and subsequent disruption of tight junctions of HT29-MTX cell model compared with the Caco-2 and HT-29 cell models. Data from this study suggest that the HT29-MTX cell model, with more physiologically relevant characteristics with the mucus layer formation, could be better suited for studying cells–pathogens interactions.     

Lactobacillus casei NY1301 Increases the Adhesion of Lactobacillus gasseri NY0509 to Human Intestinal Caco-2 Cells

In the presence of Lactobacillus casei NY1301, the adhesion of Lactobacillus gasseri NY0509 to cultured human intestinal Caco-2 cells was significantly increased (P<0.01). In contrast, L. gasseri NY0509 did not affect the adhesion of L. casei NY1301. A heat-stable cell component of L. casei NY1301 was involved in this increase of adhesion. These results suggest that a combination of these strains may have synergistic effects of adhesion to human intestinal mucosa.     

罗伊氏乳杆菌肠道分离株的遗传多样性研究

动物体内定殖着丰富且多样的细菌,其对宿主的健康发挥着举足轻重的作用。罗伊氏乳杆菌(Lactobacillus reuteri)是存在于动物肠道中的益生菌,是研究肠道菌群与宿主进化关系的模式菌种。【目的】以下载自NCBI的分离自猪、家禽类、人类、啮齿类动物的116株L.reuteri和分离自内蒙古锡林郭勒牛、羊和马肠道中的16株L. reuteri为研究对象,解析L. reuteri不同分离株的遗传多样性和宿主特异性,为L. reuteri的开发利用提供理论依据。【方法】利用MLST技术,以ddl、pkt、leu S、gyr B、dlt A、rpo A、rec A共7个看家基因为研究靶点,对L.reuteri分离株遗传多样性进行研究,推演分离株与宿主生境的进化关系。【结果】132株L. reuteri共划分为63个序列型,6个克隆复合体。等位基因序列重组分析发现,在L.reuteri的进化中发生了个别的重组事件,eBURST、MSTree分析表明不同分离源的L. reuteri分离株经历了不同的进化过程,系统发育分析表明132株L. reuteri来自5个Clusters且与分离源表现出较强的相关性。【结论】本研究利用MLST技术完成了132株L. reuteri肠道分离株的遗传多样性分析,利用MSTree、系统发育等群体结构分析,发现不同分离源菌株有着高度的宿主特异性,表明L. reuteri为适应不同生存环境经历了不同的进化过程。     

The influence of polyunsaturated fatty acids on probiotic growth and adhesion

The establishment of the intestinal microflora, and probiotic bacteria, may control the inflammatory conditions in the gut. As polyunsaturated fatty acids (PUFA) possess antimicrobial activities, they may deter the action of probiotics. We assessed whether free linoleic, gamma-linolenic, arachidonic, alpha-linolenic and docosahexaenoic acids at physiological concentrations in the growth media would influence the growth and adhesion of Lactobacillus GG (probiotic), Lactobacillus casei Shirota (probiotic) and Lactobacillus bulgaricus (dairy strain). Higher concentrations of PUFA (10-40 microg PUFA ml(-1)) inhibited growth and mucus adhesion of all tested bacterial strains, whilst growth and mucus adhesion of L. casei Shirota was promoted by low concentrations of gamma-linolenic acid and arachidonic acid (at 5 microg ml(-1)), respectively. PUFA also altered bacterial adhesion sites on Caco-2 cells. Caco-2 cells grown in the presence of arachidonic acid were less adhered to by all three bacterial strains. Yet, L. casei Shirota adhered better on Caco-2 cells grown in the presence of alpha-linolenic acid. As the adhesion to mucosal surfaces is pivotal in health promoting effects by probiotics, our results indicate that the action of probiotics in the gut may be modulated by dietary PUFA.