Xylitol and erythritol inhibit real-time biofilm formation of Streptococcus mutans

Background: Regular consumption of xylitol decreases the number of cariogenic streptococci in dental plaque. In vitro biofilm models to study the mechanism of xylitol action have been set-up, but the obtained results are contradictory. Biofilm growth is a dynamic process with time-specific characteristics that may remain undetected in conventional end-point biofilm tests. In this study we used an impedance spectroscopy instrument, xCELLigence Real Time Cell Analyzer (RTCA), that allows label-free, non-invasive real-time monitoring of biofilm formation, to explore effects of xylitol on biofilm formation by Streptococcus mutans. Based on the obtained information of biofilm dynamics, we assessed the number of viable bacteria, the polysaccharide content, and the expression levels of selected genes involved in glucan-mediated biofilm formation in different biofilm stages. Xylitol inhibition was compared with that of erythritol; another polyol suggested to have a positive impact on oral health.Results: Our results showed that real-time monitoring provided new information of polyol-induced changes in S. mutans biofilm formation dynamics. The inhibitory effect of polyols was more pronounced in the early stages of biofilm formation but affected also the measured total amount of formed biofilm. Effects seen in the real-time biofilm assay were only partially explained by changes in CFU values and polysaccharide amounts in the biofilms. Both xylitol and erythritol inhibited real-time biofilm formation by all the nine tested S. mutans strains. Sensitivity of the strains to inhibition varied: some were more sensitive to xylitol and some to erythritol. Xylitol also modified the expression levels of gbpB, gtfB, gtfC and gtfD genes that are important in polysaccharide-mediated adherence of S. mutans.Conclusion: The erythritol- and xylitol- induced inhibition of biofilm formation was only partly explained by decrease in the number of viable S. mutans cells or the amount of polysaccharides in the biofilm matrix, suggesting that in addition to reduced proliferation also the matrix composition and thereby the surface attachment quality of biofilm matrix may be altered by the polyols.</div

Structures of SALSA/DMBT1 SRCR domains reveal the conserved ligand-binding mechanism of the ancient SRCR fold

The scavenger receptor cysteine-rich (SRCR) family of proteins comprises more than 20 membrane-associated and secreted molecules. Characterised by the presence of one or more copies of the similar to 110 amino-acid SRCR domain, this class of proteins have widespread functions as antimicrobial molecules, scavenger receptors, and signalling receptors. Despite the high level of structural conservation of SRCR domains, no unifying mechanism for ligand interaction has been described. The SRCR protein SALSA, also known as DMBT1/gp340, is a key player in mucosal immunology. Based on detailed structural data of SALSA SRCR domains 1 and 8, we here reveal a novel universal ligand-binding mechanism for SALSA ligands. The binding interface incorporates a dual cation-binding site, which is highly conserved across the SRCR superfamily. Along with the well-described cation dependency on most SRCR domain-ligand interactions, our data suggest that the binding mechanism described for the SALSA SRCR domains is applicable to all SRCR domains. We thus propose to have identified in SALSA a conserved functional mechanism for the SRCR class of proteins

Edible films based on milk proteins release effectively active immunoglobulins

Objectives: The goal of this study was to develop novel compositions of edible protein coatings based on immunoglobulin (Ig) fraction from bovine milk. Protein coatings can be used to protect foods against microbial, chemical, and physical damage. We developed novel compositions of edible protein coatings based on immunoglobulin (Ig) fraction from bovine milk. A lot of Ig could be obtained from under-utilized side streams of dairy industry. To the best of our knowledge, such use of the Ig fraction has not been published earlier.Materials and Methods: Bovine colostral Ig's were incorporated in edible films based on various milk proteins and investigated the characteristics of the films including solubility of Ig's and nisin and on technological properties of films. Ig's specific to cariogenic bacteria Streptococcus mutans and Streptococcus sobrinus were produced to colostrums by hyperimmunizing cows before parturition.Results: The milk Ig rich fraction suited well as a component of milk protein films. The Ig's dissolved from the films very rapidly. Nisin, commoly used for food protection, was used as a model of antimicrobial peptide. Nisin was released biologically active from both beta-lactoglobulin (beta-lg) and beta-lg/Ig films. Nisin exerted its bactericidal effect at clearly lower concentrations in the beta-lg/Ig films when compared with beta-lg film. Nisin also retained its activity better in film containing Ig-enriched whey. Incorporating Ig-enriched whey into films enhanced adhesion and tensile strength of the films. The Ig-enriched whey also affected strongly on the appearance of films based on commercial whey protein concentrate in a dose-dependent way by making the films more smooth, transparent, and clear which are all favoured properties in most food and pharmaceutical applications.Conclusions: Biologically active Ig's can be successfully incorporated in and released from milk protein based edible films. The content of Igs in films affected considerably technological properties of these films. Composition of other proteins in films had effect on preservability and release of Igs.</div

New Assembly, Reannotation and Analysis of the Entamoeba histolytica Genome Reveal New Genomic Features and Protein Content Information

Entamoeba histolytica is an anaerobic parasitic protozoan that causes amoebic dysentery. The parasites colonize the large intestine, but under some circumstances may invade the intestinal mucosa, enter the bloodstream and lead to the formation of abscesses such amoebic liver abscesses. The draft genome of E. histolytica, published in 2005, provided the scientific community with the first comprehensive view of the gene set for this parasite and important tools for elucidating the genetic basis of Entamoeba pathogenicity. Because complete genetic knowledge is critical for drug discovery and potential vaccine development for amoebiases, we have re-examined the original draft genome for E. histolytica. We have corrected the sequence assembly, improved the gene predictions and refreshed the functional gene assignments. As a result, this effort has led to a more accurate gene annotation, and the discovery of novel features, such as the presence of genome segmental duplications and the close association of some gene families with transposable elements. We believe that continuing efforts to improve genomic data will undoubtedly help to identify and characterize potential targets for amoebiasis control, as well as to contribute to a better understanding of genome evolution and pathogenesis for this parasite

Alkalizing Reactions Streamline Cellular Metabolism in Acidogenic Microorganisms

An understanding of the integrated relationships among the principal cellular functions that govern the bioenergetic reactions of an organism is necessary to determine how cells remain viable and optimise their fitness in the environment. Urease is a complex enzyme that catalyzes the hydrolysis of urea to ammonia and carbonic acid. While the induction of urease activity by several microorganisms has been predominantly considered a stress-response that is initiated to generate a nitrogen source in response to a low environmental pH, here we demonstrate a new role of urease in the optimisation of cellular bioenergetics. We show that urea hydrolysis increases the catabolic efficiency of Streptococcus thermophilus, a lactic acid bacterium that is widely used in the industrial manufacture of dairy products. By modulating the intracellular pH and thereby increasing the activity of β-galactosidase, glycolytic enzymes and lactate dehydrogenase, urease increases the overall change in enthalpy generated by the bioenergetic reactions. A cooperative altruistic behaviour of urease-positive microorganisms on the urease-negative microorganisms within the same environment was also observed. The physiological role of a single enzymatic activity demonstrates a novel and unexpected view of the non-transcriptional regulatory mechanisms that govern the bioenergetics of a bacterial cell, highlighting a new role for cytosol-alkalizing biochemical pathways in acidogenic microorganisms

Innate immunity glycoprotein gp-340 variants may modulate human susceptibility to dental caries

<p>Abstract</p> <p>Background</p> <p>Bacterial adhesion is an important determinant of colonization and infection, including dental caries. The salivary scavenger receptor cysteine-rich glycoprotein gp-340, which mediates adhesion of <it>Streptococcus mutans </it>(implicated in caries), harbours three major size variants, designated gp-340 I to III, each specific to an individual saliva. Here we have examined the association of the gp-340 I to III polymorphisms with caries experience and adhesion of <it>S. mutans</it>.</p> <p>Methods</p> <p>A case-referent study was performed in 12-year-old Swedish children with high (n = 19) or low (n = 19) caries experiences. We measured the gp-340 I to III saliva phenotypes and correlated those with multiple outcome measures for caries experience and saliva adhesion of <it>S. mutans </it>using the partial least squares (PLS) multivariate projection technique. In addition, we used traditional statistics and 2-year caries increment to verify the established PLS associations, and bacterial adhesion to purified gp-340 I to III proteins to support possible mechanisms.</p> <p>Results</p> <p>All except one subject were typed as gp-340 I to III (10, 23 and 4, respectively). The gp-340 I phenotype correlated positively with caries experience (VIP = 1.37) and saliva adhesion of <it>S. mutans </it>Ingbritt (VIP = 1.47). The gp-340 II and III phenotypes tended to behave in the opposite way. Moreover, the gp-340 I phenotype tended to show an increased 2-year caries increment compared to phenotypes II/III. Purified gp-340 I protein mediated markedly higher adhesion of <it>S. mutans </it>strains Ingbritt and NG8 and <it>Lactococcus lactis </it>expressing AgI/II adhesins (SpaP or PAc) compared to gp-340 II and III proteins. In addition, the gp-340 I protein appeared over represented in subjects positive for Db, an allelic acidic PRP variant associated with caries, and subjects positive for both gp-340 I and Db tended to experience more caries than those negative for both proteins.</p> <p>Conclusion</p> <p>Gp-340 I behaves as a caries susceptibility protein.</p

Xylitol and erythritol inhibit real-time biofilm formation of Streptococcus mutans

Background: Regular consumption of xylitol decreases the number of cariogenic streptococci in dental plaque. In vitro biofilm models to study the mechanism of xylitol action have been set-up, but the obtained results are contradictory. Biofilm growth is a dynamic process with time-specific characteristics that may remain undetected in conventional end-point biofilm tests. In this study we used an impedance spectroscopy instrument, xCELLigence Real Time Cell Analyzer (RTCA), that allows label-free, non-invasive real-time monitoring of biofilm formation, to explore effects of xylitol on biofilm formation by Streptococcus mutans. Based on the obtained information of biofilm dynamics, we assessed the number of viable bacteria, the polysaccharide content, and the expression levels of selected genes involved in glucan-mediated biofilm formation in different biofilm stages. Xylitol inhibition was compared with that of erythritol; another polyol suggested to have a positive impact on oral health. Results: Our results showed that real-time monitoring provided new information of polyol-induced changes in S. mutans biofilm formation dynamics. The inhibitory effect of polyols was more pronounced in the early stages of biofilm formation but affected also the measured total amount of formed biofilm. Effects seen in the real-time biofilm assay were only partially explained by changes in CFU values and polysaccharide amounts in the biofilms. Both xylitol and erythritol inhibited real-time biofilm formation by all the nine tested S. mutans strains. Sensitivity of the strains to inhibition varied: some were more sensitive to xylitol and some to erythritol. Xylitol also modified the expression levels of gbpB, gtfB, gtfC and gtfD genes that are important in polysaccharide-mediated adherence of S. mutans. Conclusion: The erythritol- and xylitol- induced inhibition of biofilm formation was only partly explained by decrease in the number of viable S. mutans cells or the amount of polysaccharides in the biofilm matrix, suggesting that in addition to reduced proliferation also the matrix composition and thereby the surface attachment quality of biofilm matrix may be altered by the polyols

Structures of SALSA/DMBT1 SRCR domains reveal the conserved ligand-binding mechanism of the ancient SRCR-fold

The scavenger receptor cysteine-rich (SRCR) family of proteins comprises more than 20 membrane-associated and secreted molecules. Characterised by the presence of one or more copies of the ∼110 amino-acid SRCR domain, this class of proteins have widespread functions as antimicrobial molecules, scavenger receptors, and signalling receptors. Despite the high level of structural conservation of SRCR domains, no unifying mechanism for ligand interaction has been described. The SRCR protein SALSA, also known as DMBT1/gp340, is a key player in mucosal immunology. Based on detailed structural data of SALSA SRCR domains 1 and 8, we here reveal a novel universal ligand-binding mechanism for SALSA ligands. The binding interface incorporates a dual cation-binding site, which is highly conserved across the SRCR superfamily. Along with the well-described cation dependency on most SRCR domain–ligand interactions, our data suggest that the binding mechanism described for the SALSA SRCR domains is applicable to all SRCR domains. We thus propose to have identified in SALSA a conserved functional mechanism for the SRCR class of proteins

Stability of activity of bovine colostrum derived anti-caries streptococci antibodies added to a UHT milk product

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