Interaction of bifidobacterial lipoteichoic acid with human intestinal epithelial cells

The impact of aging-induced gut microbiome dysbiosis on dendritic cells and lung diseases

Aging is an inevitable natural process that impacts every individual, and understanding its effect on the gut microbiome and dendritic cell (DC) functionality in elderly subjects is crucial. DCs are vital antigen-presenting cells (APCs) that orchestrate the immune response, maintaining immune tolerance to self-antigens and bridging innate and adaptive immunity. With aging, there is a shift toward nonspecific innate immunity, resulting in a decline in adaptive immune responses. This alteration raises significant concerns about managing the health of an elderly population. However, the precise impact of aging and microbiome changes on DC function and their implications in lung-associated diseases remain relatively understudied. To illuminate this subject, we will discuss recent advancements in understanding the connections between aging, gut dysbiosis, DCs, and lung diseases. Emphasizing the key concepts linking age-related gut microbiome changes and DC functions, we will focus on their relevance to overall health and immune response in elderly individuals. This article aims to improve our understanding of the intricate relationship between aging, gut microbiome, and DCs, potentially benefiting the management of age-associated diseases and promoting healthy aging.

Cracking the intestinal lymphatic system window utilizing oral delivery vehicles for precise therapy

Oral administration is preferred over other drug delivery methods due to its safety, high patient compliance, ease of ingestion without discomfort, and tolerance of a wide range of medications. However, oral drug delivery is limited by the poor oral bioavailability of many drugs, caused by extreme conditions and absorption challenges in the gastrointestinal tract. This review thoroughly discusses the targeted drug vehicles to the intestinal lymphatic system (ILS). It explores the structure and physiological barriers of the ILS, highlighting its significance in dietary lipid and medication absorption and transport. The review presents various approaches to targeting the ILS using spatially precise vehicles, aiming to enhance bioavailability, achieve targeted delivery, and reduce first-pass metabolism with serve in clinic. Furthermore, the review outlines several methods for leveraging these vehicles to open the ILS window, paving the way for potential clinical applications in cancer treatment and oral vaccine delivery. By focusing on targeted drug vehicles to the ILS, this article emphasizes the critical role of these strategies in improving therapeutic efficacy and patient outcomes. Overall, this article emphasizes the critical role of targeted drug vehicles to the ILS and the potential impact of these strategies on improving therapeutic efficacy and patient outcomes.

Health-Promoting Nature of Lactococcus lactis IBB109 and Lactococcus lactis IBB417 Strains Exhibiting Proliferation Inhibition and Stimulation of Interleukin-18 Expression in Colorectal Cancer Cells

Lactic acid bacteria (LAB) are Gram-positive bacteria which are considered for use as adjuvant therapeutics in management of various disease ailments, including obesity, irritable bowel syndrome, lactose intolerance and cancer. To investigate the possible use of Lactococcus lactis strains from our collection in treatment of gastrointestinal cancer, we tested them for the ability to arrest proliferation of human colorectal adenocarcinoma cells (Caco-2). Results of the BrdU assay showed that the anti-proliferative activity of L. lactis cells is strain-specific. We found that particularly, two strains, L. lactis IBB109 and L. lactis IBB417, exhibited the most potent inhibitory effect. Moreover, both strains triggered interleukin 18 gene expression, normally inhibited in Caco-2 (cancer) cells. To examine the probiotic potential of the two strains, we tested them for bile salts and acid tolerance, as well as adhesion properties. Both isolates exhibited probiotic potential—they survived in the presence of 0.3% bile salts and tolerated exposure to low pH and osmotic stress. Notably, we found that L. lactis IBB417 displayed better adherence to mucus and Caco-2 cells than L. lactis IBB109. Additionally, by microdilution tests we confirmed that both strains are sensitive to all nine antibiotics of human and veterinary importance listed by the European Food Safety Authority. Finally, by in silico investigations of whole genome sequencing data, we revealed the genetic features of L. lactis IBB109 and L. lactis IBB417 that can be associated with functional (e.g., adhesion and carbohydrate metabolic genes) and safety (e.g., virulence and antibiotic resistance) aspects of the strains, confirming their health-promoting potential.

Bifidobacterium spp. as functional foods: A review of current status, challenges, and strategies

Members of Bifidobacterium are among the first microbes to colonize the human intestine naturally, their abundance and diversity in the colon are closely related to host health. Recently, the gut microbiota has been gradually proven to be crucial mediators of various metabolic processes between the external environment and the host. Therefore, the health-promoting benefits of Bifidobacterium spp. and their applications in food have gradually been widely concerned. The main purpose of this review is to comprehensively introduce general features, colonization methods, and safety of Bifidobacterium spp. in the human gut, highlighting its health benefits and industrial applications. On this basis, the existing limitations and scope for future research are also discussed. Bifidobacteria have beneficial effects on the host's digestive system, immune system, and nervous system. However, the first prerequisite for functioning is to have enough live bacteria before consumption and successfully colonize the colon after ingestion. At present, strain breeding, optimization (e.g., selecting acid and bile resistant strains, adaptive evolution, high cell density culture), and external protection technology (e.g., microencapsulation and protectants) are the main strategies to address these challenges in food application.

Recent advances in the concept of paraprobiotics: Nutraceutical/functional properties for promoting children health

Probiotics consumption has been associated with various health promoting benefits, including disease prevention and even treatment by modulating gut microbiota. Contrary to this, probiotics may also overstimulate the immune system, trigger systemic infections, harmful metabolic activities, and promote gene transfer. In children, the fragile immune system and impaired intestinal barrier may boost the occurrence of adverse effects following probiotics' consumption. To overcome these health challenges, the key focus has been shifted toward non-viable probiotics, also called paraprobiotics. Cell wall polysaccharides, peptidoglycans, surface proteins and teichoic acid present on cell's surface are involved in the interaction of paraprobiotics with the host, ultimately providing health benefits. Among other benefits, paraprobiotics possess the ability to regulate innate and adaptive immunity, exert anti-adhesion, anti-biofilm, anti-hypertensive, anti-inflammatory, antioxidant, anti-proliferative, and antagonistic effects against pathogens, while also enhance clinical impact and general safety when administered in children in comparison to probiotics. Clinical evidence have underlined the paraprobiotics impact in children and young infants against atopic dermatitis, respiratory and gastrointestinal infections, in addition to be useful for immunocompromised individuals. Therefore, this review focuses on probiotics-related issues in children's health and also discusses the Lactobacillus and Bifidobacterium spp. qualities for qualifying as paraprobiotics and their role in promoting the children's health.

Prolonged Heat Stress of Lactobacillus paracasei GCRL163 Improves Binding to Human Colorectal Adenocarcinoma HT-29 Cells and Modulates the Relative Abundance of Secreted and Cell Surface-Located Proteins

Lactobacillus casei group bacteria improve cheese ripening and may interact with host intestinal cells as probiotics, where surface proteins play a key role. Three complementary methods [trypsin shaving (TS), LiCl-sucrose (LS) extraction, and extracellular culture fluid precipitation] were used to analyze cell surface proteins of Lactobacillus paracasei GCRL163 by label-free quantitative proteomics after culture to the mid-exponential phase in bioreactors at pH 6.5 and temperatures of 30-45 °C. A total of 416 proteins, including 300 with transmembrane, cell wall anchoring, and secretory motifs and 116 cytoplasmic proteins, were quantified as surface proteins. Although LS caused significantly greater cell lysis as growth temperature increased, higher numbers of extracytoplasmic proteins were exclusively obtained by LS treatment. Together with the increased positive surface charge of cells cultured at supra-optimal temperatures, proteins including cell wall hydrolases Msp1/p75 and Msp2/p40, α-fucosidase AlfB, SecA, and a PspC-domain putative adhesin were upregulated in surface or secreted protein fractions, suggesting that cell adhesion may be altered. Prolonged heat stress (PHS) increased binding of L. paracasei GCRL163 to human colorectal adenocarcinoma HT-29 cells, relative to acid-stressed cells. This study demonstrates that PHS influences cell adhesion and relative abundance of proteins located on the surface, which may impact probiotic functionality, and the detected novel surface proteins likely linked to the cell cycle and envelope stress.

Bifidobacteria cell wall-derived exo-polysaccharides, lipoteichoic acids, peptidoglycans, polar lipids and proteins - their chemical structure and biological attributes

A variety of health benefits has been documented to be associated with the consumption of probiotic bacteria, namely bifidobacteria and lactobacilli. Thanks to the scientific advances in recent years we are beginning to understand the molecular mechanisms by which bacteria in general and probiotic bacteria in particular act as host physiology and immune system modulators. More recently, the focus has shifted from live bacteria towards bacteria-derived defined molecules, so called postbiotics. These molecules may represent safer alternative compared to the live bacteria while retaining the desired effects on the host. The excellent source of effector macromolecules is the bacterial envelope. It contains compounds that are pivotal in the adhesion phenomenon, provide direct bacteria-to-host signaling capacity and the associated physiological impact and immunomodulatory properties of bacteria. Here we comprehensively review the structure and biological role of Bifidobacterium surface and cell wall molecules: exopolysaccharides, cell wall polysaccharides, lipoteichoic acids, polar lipids, peptidoglycans and proteins. We discuss their involvement in direct signaling to the host cells and their described immunomodulatory effects.

Survival of Microencapsulated Probiotic Bacteria after Processing and during Storage: A Review

The use of live probiotic bacteria as food supplement has become popular. Capability of probiotic bacteria to be kept at room temperature becomes necessary for customer's convenience and manufacturer's cost reduction. Hence, production of dried form of probiotic bacteria is important. Two common drying methods commonly used for microencapsulation are freeze drying and spray drying. In spite of their benefits, both methods have adverse effects on cell membrane integrity and protein structures resulting in decrease in bacterial viability. Microencapsulation of probiotic bacteria has been a promising technology to ensure bacterial stability during the drying process and to preserve their viability during storage without significantly losing their functional properties such acid tolerance, bile tolerance, surface hydrophobicity, and enzyme activities. Storage at room temperatures instead of freezing or low temperature storage is preferable for minimizing costs of handling, transportation, and storage. Concepts of water activity and glass transition become important in terms of determination of bacterial survival during the storage. The effectiveness of microencapsulation is also affected by microcapsule materials. Carbohydrate- and protein-based microencapsulants and their combination are discussed in terms of their protecting effect on probiotic bacteria during dehydration, during exposure to harsh gastrointestinal transit and small intestine transit and during storage.

FACTORS OF ADHESION OF BIFIDOBACTERIA

Data on fimbrial and afimbrial adhesion factors of bifidobacteria are presented. Pili-like structures, their composition and conditions of formation in various species of bifidobacteria are described. Several sugar-lytic enzymes serve as afimbrial adhesins in bifidobacteria. Transaldolase and enolase are detected in bifidobacteria on cells’ surface. Transaldolase ensures binding of bifidobacteria with mucin and their auto-aggregation. Surface enolase has an affinity to plasminogen, thus bifidobacteria obtain a surface-bound protein with proteolytic activity. Molecular structures giving bifidobacteria hydrophobic properties are described - surface lipoprotein Bop A and lipoteichoic acids.

Identification of surface-associated proteins of Bifidobacterium animalis ssp. lactis KLDS 2.0603 by enzymatic shaving

Bifidobacteria are commensal microorganisms of the human and animal intestinal tract, and their surface proteins can mediate bacterial communication and chemical sensing in the environment, as well as facilitate interactions between bacteria and the host. However, a systematic study of the outer surface-associated proteome of bifidobacteria has not been undertaken. In the present study, the proteins located on the surface of Bifidobacterium animalis ssp. lactis KLDS 2.0603 were systematically identified by a nongel proteomic approach, which consisted of the shaving of the bacterial surface with trypsin and an analysis of the released peptides by liquid chromatography-tandem mass spectrometry. A total of 105 surface-associated proteins were found, of which 15 proteins could potentially be involved in adhesion and interactions between bifidobacteria and the host. The proteins related to adhesion and interaction between bacteria and the host include pilus structure proteins (Fim A, Fim B), 10 moonlighting proteins, an NLP/P60 family protein, an immunogenic secreted protein, and a putative sugar-binding secreted protein. The results provide the basis for future studies on the molecular mechanisms of the interactions between bifidobacteria and the host.

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.

Effects of lactitol on intestinal microflora and plasma endotoxin in patients with chronic viral hepatitis

OBJECTIVES

To investigate the effects of lactitol on intestinal flora and the levels of plasma endotoxin in patients with chronic viral hepatitis.

METHODS

Sixty patients with chronic viral hepatitis and gut-derived endotoxemia were randomly divided into two groups: lactitol group (n=30) and control group (n=30). Patients in the control group received standard medical treatment for 3 weeks, while patients in the lactitol group received lactitol orally in addition to the standard medical treatment. Fecal flora and plasma endotoxin were measured before and after the treatment.

RESULTS

In the lactitol group, the numbers of Bifidobacterium and Lactobacillus per gram of wet feces were significantly increased (p<0.01) and Clostridium perfringens count was decreased markedly (p<0.001). The levels of plasma endotoxin decreased after the treatment from 72.89 ng/L to 33.33 ng/L in the lactitol group and from 66.00 ng/L to 51.07 ng/L in the control group, but the plasma endotoxin levels in the lactitol group decreased far more than in the control group (p<0.01).

CONCLUSIONS

Lactitol can decrease the levels of plasma endotoxin more effectively than standard medical treatment in patients with chronic viral hepatitis through improving intestinal microflora.

Bifidobacterial lipoglycan as a new cause for false-positive platelia Aspergillus enzyme-linked immunosorbent assay reactivity

We previously hypothesized that a lipoglycan of Bifidobacterium bifidum subsp. pennsylvanicum cross-reacts with the Platelia Aspergillus (PA) enzyme-linked immunosorbent assay (ELISA) based on the presence of galactofuranosyl epitopes in the cell wall (M. A. S. H. Mennink-Kersten, R. R. Klont, A. Warris, H. J. M. Op den Camp, and P. E. Verweij, Lancet 363:325-327, 2004). We tested this hypothesis by testing bacterial suspensions of different bifidobacterial species and other gram-positive and -negative bacteria with the PA ELISA, which is used to detect circulating galactomannan for the serodiagnosis of invasive aspergillosis. Furthermore, neonatal fecal samples were enumerated for bifidobacteria by fluorescence in situ hybridization (FISH) and tested for PA ELISA reactivity. All bifidobacteria, except B. infantis and B. adolescentis, showed reactivity 6- to 600-fold higher compared to the controls (i.e., Micrococcus luteus and Propionibacterium freudenreichii, which contain a cell wall lipomannan). Eggerthella lenta showed a 25-fold-higher reactivity. ELISA reactivity was clearly shown to be associated with bacterial lipoglycans containing a beta-1,5-galactofuranosyl chain. All neonatal feces showed PA ELISA reactivity and associated numbers of bifidobacteria. Since high concentrations of bifidobacteria are present in the human gut, these bacteria or excreted lipoglycan may cause false serum PA ELISA reactivity in selected patient groups, especially neonates.

Apolipophorin-III and the interactions of lipoteichoic acids with the immediate immune responses of Galleria mellonella

We investigated the effects of lipoteichoic acids, surface components of Gram-positive bacteria, on the hemocytes and phenoloxidase activity in last instar Galleria mellonella larvae, as well as the binding of apolipophorin-III, an insect lipid-binding protein, to lipoteichoic acids. Binding of apolipophorin-III to lipoteichoic acid was studied using an assay based on 1,9-dimethylmethylene blue. Apolipophorin-III bound the lipoteichoic acids from Bacillus subtilis, Enterococcus hirae, and Streptococcus pyogenes and to intact cells of E. hirae. E. hirae lipoteichoic acid promoted the binding of apolipophorin-III to the cells of this species. All lipoteichoic acids tested caused a dose- and time-dependent drop in the total counts of hemocytes and, depending on the species of lipoteichoic acid, partial or complete depletion of plasmatocytes. Granulocyte counts were not affected. Apolipophorin-III prevented partially the loss of plasmatocytes due to B. subtilis lipoteichoic acid. All three lipoteichoic acids studied activated phenoloxidase in vitro; injections of B. subtilis lipoteichoic acid into the larvae elevated the phenoloxidase activity, whereas injections of E. hirae or S. pyogenes lipoteichoic acid, or apolipophorin-III alone, suppressed it. Apolipophorin-III decreased the activation of phenoloxidase by B. subtilis lipoteichoic acid.

Probiotics and prebiotics: can regulating the activities of intestinal bacteria benefit health?

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Cell surface-associated lipoteichoic acid acts as an adhesion factor for attachment of Lactobacillus johnsonii La1 to human enterocyte-like Caco-2 cells

The influence of pH on the adhesion of two Lactobacillus strains to Caco-2 human intestinal cells was investigated. One strain, Lactobacillus johnsonii La1, was adherent at any pH between 4 and 7. The other one, L. acidophilus La10, did not attach to this cell line under the same experimental conditions. On the basis of these results, we used the monoclonal antibody technique as a tool to determine differences on the surface of these bacteria and to identify a factor for adhesion. Mice were immunized with live La1, and the hybridomas produced by fusion of spleen cells with ONS1 cells were screened for the production of antibodies specific for L. johnsonii La1. A set of these monoclonal antibodies was directed against a nonproteinaceous component of the L. johnsonii La1 surface. It was identified as lipoteichoic acid (LTA). This molecule was isolated, chemically characterized, and tested in adhesion experiments in the same system. The adhesion of L. johnsonii La1 to Caco-2 cells was inhibited in a concentration-dependent way by purified LTA as well as by L. johnsonii La1 culture supernatant that contained LTA. These results showed that the mechanism of adhesion of L. johnsonii La1 to human Caco-2 cells involves LTA.

Isolation and characterization of exocellular polysaccharides produced by Bifidobacterium longum

When grown anaerobically at pH values above 5.0, on ultrafiltered complex media containing excess lactose, Bifidobacterium longum formed up to 140 mg l-1 (glucose equiv.) exopolysaccharides. The highest yield was obtained when the cells were cultivated in a peptone/yeast extract medium with pH controlled by additions of NH4OH. Whatever the conditions under study, exopolysaccharides represented about 30% of the polysaccharides produced by B. longum after 48 h of culture. Crude pronase-treated exopolysaccharide preparations were adsorbed on ion-exchange chromatographic resin to yield an anionic heteropolysaccharide fraction. Two subfractions with apparent molecular masses of 1.2 MDa and 0.36 MDa respectively were subsequently recovered after gel filtration on Sepharose 4B. In both subfractions, glucose, galactose and small amounts of uronic acids and hexosamines were present in similar molar proportions, suggesting that the excreted polymers may be synthesized from the same base unit and may have a structure resulting from repeating subunits.

Performance of single comb White Leghorn layers fed corn-soybean meal and barley-corn-soybean meal diets supplemented with a direct-fed microbial

An experiment was conducted with Single Comb White Leghorn (SCWL) layers to determine the effect of feeding either corn-soybean meal (C-S) or barley-corn soybean meal (B-C-S) diets with or without condensed cane molasses solubles (CCMS) or with or without CCMS-1,100 mg Lactobacillus (Lacto)/kg (ppm) diet on performance, nutrient retentions, digesta passage rate, and histological changes of the gastrointestinal (GI) tracts. Six dietary treatments were fed for eight 28-d periods and consisted of C-S (control), C-S + CCMS, C-S + CCMS-1,100 ppm Lacto (4.4 x 107 cfu/mg Lacto), B-C-S (control), B-C-S + CCMS, and B-C-S + CCMS-1,100 ppm Lacto. The CCMS served as the carrier for the Lacto, and the CCMS-Lacto premix (55 g Lacto/kg) was incorporated at 2% of the diet. Lactobacillus supplementation in C-S diets improved (P < .05) egg weight, egg mass, egg size, and body weight gains, and in B-C-S diets improved body weight gains. There were no differences in feed consumption, feed conversion, internal egg quality, and egg specific gravity among the dietary treatments. Passage rates of digesta were increased (P < .05) when either C-S or B-C-S layer diets were supplemented with Lacto. Lactobacillus supplementations of the C-S and B-C-S diets increased (P < .05) fat and calcium, and fat, phosphorus, copper, and manganese retentions, respectively. Increased cellularity of Peyer's patches in the ileum indicated a stimulation of the mucosal immune system that responds to antigenic stimuli by secreting immunoglobulin (IgA).

Bifidobacterial cell wall proteins (BIFOP) in Bifidobacterium globosum

Nearly 150 strains of Bifidobacterium globosum were isolated from faeces of calf, chicken, lamb, rabbit and rat, from sewage, from rumen content and from human infant faeces between 1962 and 1973 and scored by SDS-PAGE for the presence of cell-wall-related proteins, i.e. BIFOP (bifid outer proteins); their apparent molecular masses ranged from 94.5 to 34 kDa and were designated A to L. Purified preparations from six of these ten proteins were employed to produce polyclonal rabbit antisera for use in immunoblots to investigate the interrelationships of the major antigens, A, B and C (94.5-85.5 kDa) and their distribution in strains of various origin. Two antigens differently migrating (or polymorphic forms) reacted with anti-BIFOP F serum (called F- and F+); the identity of BIFOP E with respect to these antigens was studied with anti-E serum. Only one antigen in all strain preparations reacted to anti-BIFOP H serum, which was raised against an antigen purified from a 13.5-MDa plasmid-bearing strain from rumen.

Deposition of circulating streptococcal lipoteichoic acid in mouse tissues

The tissue binding properties of streptococcal lipoteichoic acid (LTA) were studied using normal and passively immunized BALB/c mice. After intraperitoneal injection in non-immunized mice, 3H-LTA concentrations in blood, heart, kidney and liver were highest between 24 and 30 h post-injection. LTA deposits in heart remained high for the next 24 h, whereas other tissue levels decreased. Constant amounts of 3H-LTA were detected in urine throughout the 48 h period. In passively immunized mice, the amount of tissue deposition of 3H-LTA was inversely proportional to the ratio of antibodies to LTA. Autoradiography revealed focal deposits of 3H-LTA in heart, kidney and liver. These observations indicate that LTA, released by streptococci growing at remote body sites, can be carried by the blood to internal organs where it can accumulate and participate in pathogenesis.

Molecular analysis of lipoteichoic acid from Streptococcus agalactiae

A method for the analysis of lipoteichoic acid (LTA) by polyacrylamide gel electrophoresis (PAGE) is described. Purified LTA from Streptococcus agalactiae tended to smear in the upper two-thirds of a 30 to 40% linear polyacrylamide gel, while the chemically deacylated form (cdLTA) migrated as a ladder of discrete bands, reminiscent of lipopolysaccharides. The deacylated polymer appeared to separate in this system on the basis of size, as evident from results obtained from PAGE analysis of cdLTA subjected to limited acid hydrolysis and LTA that had been fractionated by gel filtration. A survey of cdLTA from other streptococci revealed similarities in molecular weight ranges. The polymer from Enterococcus hirae was of a higher molecular weight. This procedure was used to examine the effect of penicillin and chloramphenicol on the synthesis, turnover, and heterogeneity of LTA in S. agalactiae. Penicillin appeared to enhance LTA synthesis while causing the release of this polymer into the supernatant fluid. In contrast, chloramphenicol inhibited the synthesis of this molecule and resulted in its depletion from the cell surface. Penicillin did not alter the heterogeneity of this polymer, but chloramphenicol caused an apparent shift to a lower-molecular-weight from of the LTA, as determined by PAGE. This shift in the heterogeneity of LTA did not appear to be due to increased carbohydrate substitution, since chloramphenicol did not alter the electrophoretic migration profile of LTA from E. hirae. From a pulse-chase study, it was determined that LTA was released as a consequence of deacylation.

Interaction of streptococcal lipoteichoic acid with artificial tooth pellicle

Artificial pellicles were prepared by coating hydroxyapatite beads with whole saliva. Radiolabelled lipoteichoic acid was isolated from Streptococcus sanguis NCTC 7863 by phenol extraction. Various concentrations of radiolabelled lipoteichoic acid were mixed with saliva-coated hydroxyapatite in the presence and absence of high ionic strength phosphate buffer, bovine serum albumin, gelatin, unlabelled lipoteichoic acid, Tween 20 and Triton X-100. The amount of lipoteichoic acid binding was measured by counting the residual radioactivity of the saliva-coated hydroxyapatite after thorough washing. In one experiment the binding was measured in the presence of a mucinous glycoprotein isolated from human saliva. The data were analysed by means of Scatchard and double reciprocal plots of the bound and unbound fraction of lipoteichoic acid. The lipoteichoic acid interacted hydrophobically with the saliva-coated hydroxyapatite; the interaction was complex with multiple binding sites exhibiting a range of affinities. The mean association constant was 1.1 x 10(9) M-1 and the minimum number of binding sites was 3.9 x 10(12)/mm2 of artificial pellicle. The salivary mucin competitively inhibited the interaction, which suggests that this may be one of the salivary components involved.

Surface properties of lactobacilli isolated from the small intestine of pigs

One hundred wild-type strains of the genus Lactobacillus were isolated from the small intestine of newly-slaughtered pigs up to 6 months of age. Cell surface hydrophobicity and capsule formation were studied on a number of strains. Strains showing high surface hydrophobicity as measured by the salt-aggregation test and hydrophobic interaction chromatography on Octyl Sepharose were commonly found to adhere in high numbers to isolated pig intestinal epithelial cells. Heat and protease treatment of bacteria of high surface hydrophobicity, including autoaggregating strains in phosphate-buffered saline, showed a drastic decline in this surface property. Three hydrophilic strains (LBp 1044, 1068 and 1073) also showed binding to intestinal cells but at a lower level (approx. 5 bacteria/cell) as compared with the best binding hydrophobic strain (LBp 1063, approx. 11 bacteria/cell). These findings suggest that different or multiple adhesion mechanisms may be involved in the colonization of the small intestinal mucosa of pigs. Cultures of selected strains grown in liquid media rich in carbohydrates did not affect their hydrophobic cell surface character. Therefore it seems less likely that carbohydrate capsule polymers are the major determinants of intestinal colonization of lactobacilli in pigs.

Standardization of salt aggregation test for reproducible determination of cell-surface hydrophobicity with special reference to Staphylococcus species

The laboratory conditions for reproducible routine determination of staphylococcal cell-surface hydrophobicity by the salt aggregation test were standardized. Fresh bacterial suspensions standardized to 5 x 10(9) cfu/ml gave the most reproducible results with both Staphylococcus aureus and coagulase-negative staphylococci. For relatively hydrophobic strains a 5-min reading time was necessary to detect bacterial aggregation in ammonium sulphate solutions ranging from 0.1 M to 1.5 M, pH 6.8. A x 10 hand lens facilitated reading aggregations. Overnight storage of bacterial suspensions at 20 degrees C reduced cell-surface hydrophobicity of all species, while storage at 4 degrees C reduced the hydrophobic nature of Staph. aureus strains. The hydrophobicity of coagulase-negative staphylococci rarely changed at 4 degrees C. A 10-fold dilution of fresh, standardized bacterial suspensions made it impossible to detect bacterial aggregation in ammonium sulphate solutions even with a hand lens. Under standardized conditions three types of staphylococcal cell aggregations were observed. The first looked like the slide agglutination for O antigens of Enterobacteriaceae, the second resembled H-agglutination, while the third had a filamentous appearance. These patterns indicated that more than one component might contribute to cell-surface hydrophobicity of both Staph. aureus and coagulase-negative staphylococci, or the same component might have different position on the cell surface.

Cell surface hydrophobicity of Bifidobacterium bifidum subsp. pennsylvanicum

The possible role of lipoteichoic acid with respect to cell surface properties of Bifidobacterium bifidum subsp. pennsylvanicum was studied. Standard suspensions of bacteria were mixed with octane or xylene. B. bifidum subsp. pennsylvanicum was shown to possess a strongly hydrophobic cell surface. Hydrophobicity of the bacteria could be reduced by treatment with trypsin, pepsin (at pH 4.5), HCl and penicillin. The latter treatment resulted in an increased excretion of lipoteichoic acid. Albumin was capable of inhibiting the adherence to octane when it was present in the assay buffer. The data suggest that both protein and lipoteichoic acid may be involved in cell surface hydrophobicity. A great divergence in cell surface properties was observed within the genus Bifidobacterium.

Phosphatidylglycerol as biosynthetic precursor for the poly(glycerol phosphate) backbone of bifidobacterial lipoteichoic acid

Phosphatidylglycerol functions as donor of the sn-glycerol 1-phosphate units in the synthesis in vitro of the 1,2-phosphodiester-linked glycerol phosphate backbone of the lipoteichoic acids of Bifidobacterium bifidum subsp. pennsylvanicum. The incorporation was catalysed by a membrane-bound enzyme system. After addition of chloroform/methanol the product formed coprecipitated with protein. The material was phenol-extractable and was co-eluted with purified lipoteichoic acid on Sepharose 6B. The reaction was stimulated by Triton X-100, UDP-glucose and UDP-galactose, but Mg2+ ions had no effect. The apparent values for Km and Vmax. of the phosphatidylglycerol incorporation were 1.4 mM and 3.1 nmol/h per mg of membrane protein, respectively. Labelled UDP-glucose and UDP-galactose were not incorporated into the lipoteichoic acid fraction by the particulate membrane preparation.