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Lactis
Kinds of Lactis Terms modified by Lactis Selected AbstractsUniversal method for synthesis of artificial gel antibodies by the imprinting approach combined with a unique electrophoresis technique for detection of minute structural differences of proteins, viruses, and cells (bacteria).ELECTROPHORESIS, Issue 23 2006III: Gel antibodies against cells (bacteria) Abstract Artificial antibodies in the form of gel granules were synthesized from the monomers acrylamide and N,N'-methylenebisacrylamide by the imprinting method in the presence of Echerichia coli bacteria as template. The electrophoretic migration velocities of the gel antibodies (i),saturated with the antigen (Escherichia,coli MRE-600), (ii),freed of the antigen, and (iii),resaturated with bacteria, were determinated by electrophoresis in a rotating narrow-bore tube of 245,mm length and the 2.5 and 9.6,mm inner and outer diameters, respectively. Removal of bacteria from the gel antibodies was made by treatment with enzymes, followed by washing with SDS and buffer. Gel granules becoming charged by adsorption of bacteria move in an electrical field. We obtained a significant selectivity of gel antibodies for E.,coli MRE-600, since the granules did not interact with Lactococcus lactis; and when E.,coli BL21 bacteria were added to the gels selective for E.,coli MRE-600, a significant difference in the migration rate of the complexes formed with the two strains was observed indicating the ability of differentiation between the two strains. The gel antibodies can be used repeatedly. The new imprinting method for the synthesis of artificial gel antibodies against bioparticles described herein, and the classical electrophoretic analysis technique employed, thus represent , when combined , a new approach to distinguish between different types and strains of bacteria. The application area can certainly be extended to cover other classes of cells. [source] Experimental and steady-state analysis of the GAL regulatory system in Kluyveromyces lactisFEBS JOURNAL, Issue 14 2010Venkat R. Pannala The galactose uptake mechanism in yeast is a well-studied regulatory network. The regulatory players in the galactose regulatory mechanism (GAL system) are conserved in Saccharomyces cerevisiae and Kluyveromyces lactis, but the molecular mechanisms that occur as a result of the molecular interactions between them are different. The key differences in the GAL system of K. lactis relative to that of S. cerevisiae are: (a) the autoregulation of KlGAL4; (b) the dual role of KlGal1p as a metabolizing enzyme as well as a galactose-sensing protein; (c) the shuttling of KlGal1p between nucleus and cytoplasm; and (d) the nuclear confinement of KlGal80p. A steady-state model was used to elucidate the roles of these molecular mechanisms in the transcriptional response of the GAL system. The steady-state results were validated experimentally using measurements of ,-galactosidase to represent the expression for genes having two binding sites. The results showed that the autoregulation of the synthesis of activator KlGal4p is responsible for the leaky expression of GAL genes, even at high glucose concentrations. Furthermore, GAL gene expression in K. lactis shows low expression levels because of the limiting function of the bifunctional protein KlGal1p towards the induction process in order to cope with the need for the metabolism of lactose/galactose. The steady-state model of the GAL system of K. lactis provides an opportunity to compare with the design prevailing in S. cerevisiae. The comparison indicates that the existence of a protein, Gal3p, dedicated to the sensing of galactose in S. cerevisiae as a result of genome duplication has resulted in a system which metabolizes galactose efficiently. [source] Contribution of exofacial thiol groups in the reducing activity of Lactococcus lactisFEBS JOURNAL, Issue 10 2010D. Michelon Lactococcus lactis can decrease the redox potential at pH 7 (Eh7) from 200 to ,200 mV in oxygen free Man,Rogosa,Sharpe media. Neither the consumption of oxidizing compounds or the release of reducing compounds during lactic acid fermentation were involved in the decrease in Eh7 by the bacteria. Thiol groups located on the bacterial cell surface appear to be the main components that are able to establish a greater exchange current between the Pt electrode and the bacteria. After the final Eh7 (,200 mV) was reached, only thiol-reactive reagents could restore the initial Eh7 value. Inhibition of the proton motive force showed no effect on maintaining the final Eh7 value. These results suggest that maintaining the exofacial thiol (,SH) groups in a reduced state does not depend on an active mechanism. Thiol groups appear to be displayed by membrane proteins or cell wall-bound proteins and may participate in protecting cells against oxidative stress. [source] The chitinolytic system of Lactococcus lactis ssp. lactis comprises a nonprocessive chitinase and a chitin-binding protein that promotes the degradation of ,- and ,-chitinFEBS JOURNAL, Issue 8 2009Gustav Vaaje-Kolstad It has recently been shown that the Gram-negative bacterium Serratia marcescens produces an accessory nonhydrolytic chitin-binding protein that acts in synergy with chitinases. This provided the first example of the production of dedicated helper proteins for the turnover of recalcitrant polysaccharides. Chitin-binding proteins belong to family 33 of the carbohydrate-binding modules, and genes putatively encoding these proteins occur in many microorganisms. To obtain an impression of the functional conservation of these proteins, we studied the chitinolytic system of the Gram-positive Lactococcus lactis ssp. lactis IL1403. The genome of this lactic acid bacterium harbours a simple chitinolytic machinery, consisting of one family 18 chitinase (named LlChi18A), one family 33 chitin-binding protein (named LlCBP33A) and one family 20 N -acetylhexosaminidase. We cloned, overexpressed and characterized LlChi18A and LlCBP33A. Sequence alignments and structural modelling indicated that LlChi18A has a shallow substrate-binding groove characteristic of nonprocessive endochitinases. Enzymology showed that LlChi18A was able to hydrolyse both chitin oligomers and artificial substrates, with no sign of processivity. Although the chitin-binding protein from S. marcescens only bound to ,-chitin, LlCBP33A was found to bind to both ,- and ,-chitin. LlCBP33A increased the hydrolytic efficiency of LlChi18A to both ,- and ,-chitin. These results show the general importance of chitin-binding proteins in chitin turnover, and provide the first example of a family 33 chitin-binding protein that increases chitinase efficiency towards ,-chitin. [source] The crystal structure of pyruvate decarboxylase from Kluyveromyces lactisFEBS JOURNAL, Issue 18 2006Implications for the substrate activation mechanism of this enzyme The crystal structure of pyruvate decarboxylase from Kluyveromyces lactis has been determined to 2.26 Ĺ resolution. Like other yeast enzymes, Kluyveromyces lactis pyruvate decarboxylase is subject to allosteric substrate activation. Binding of substrate at a regulatory site induces catalytic activity. This process is accompanied by conformational changes and subunit rearrangements. In the nonactivated form of the corresponding enzyme from Saccharomyces cerevisiae, all active sites are solvent accessible due to the high flexibility of loop regions 106,113 and 292,301. The binding of the activator pyruvamide arrests these loops. Consequently, two of four active sites become closed. In Kluyveromyces lactis pyruvate decarboxylase, this half-side closed tetramer is present even without any activator. However, one of the loops (residues 105,113), which are flexible in nonactivated Saccharomyces cerevisiae pyruvate decarboxylase, remains flexible. Even though the tetramer assemblies of both enzyme species are different in the absence of activating agents, their substrate activation kinetics are similar. This implies an equilibrium between the open and the half-side closed state of yeast pyruvate decarboxylase tetramers. The completely open enzyme state is favoured for Saccharomyces cerevisiae pyruvate decarboxylase, whereas the half-side closed form is predominant for Kluyveromyces lactis pyruvate decarboxylase. Consequently, the structuring of the flexible loop region 105,113 seems to be the crucial step during the substrate activation process of Kluyveromyces lactis pyruvate decarboxylase. [source] The structural comparison of the bacterial PepX and human DPP-IV reveals sites for the design of inhibitors of PepX activityFEBS JOURNAL, Issue 8 2005Pascal Rigolet X-prolyl dipeptidyl aminopeptidases (X-PDAP) are enzymes catalysing the release of dipeptides from the amino termini of polypeptides containing a proline or an alanine at the penultimate position. Involved in various mammalian regulation processes, as well as in chronic human diseases, they have been proposed to play a role in pathogenicity for Streptococci. We compared the structure of X-PDAP from Lactococcus lactis (PepX) with its human counterpart DPP-IV. Despite very different overall folds, the residues most implicated for X-PDAP activity are conserved in the same positions and orientations in both enzymes, thus defining a structural signature for the X-PDAP specificity that crosses the species frontiers of evolution. Starting from this observation, we tested some inhibitors of DPP-IV on PepX activity, for which no specific inhibitor is known. We thus found that PepX was highly sensitive to valine-pyrrolidide with a KI of 9.3 µm, close to that reported in DPP-IV inhibition. We finally used the structure of PepX from L. lactis as a template for computer-based homology modeling of PepX from the pathogenic Streptococcus gordonii. Docking simulations of valine-pyrrolidide into the active site of PepX led to the identification of key residues for a rational drug design against PepX from Streptococci. These results could have applications in human health giving new perspectives to the struggle against pathogens. [source] Expression of the pyrG gene determines the pool sizes of CTP and dCTP in Lactococcus lactisFEBS JOURNAL, Issue 12 2004Casper M. Jřrgensen The pyrG gene from Lactococcus lactis encodes CTP synthase (EC 6.4.3.2), an enzyme converting UTP to CTP. A series of strains were constructed with different levels of pyrG expression by insertion of synthetic constitutive promoters with different strengths in front of pyrG. These strains expressed pyrG levels in a range from 3 to 665% relative to the wild-type expression level. Decreasing the level of CTP synthase to 43% had no effect on the growth rate, showing that the capacity of CTP synthase in the cell is in excess in a wild-type strain. We then studied how pyrG expression affected the intracellular pool sizes of nucleotides and the correlation between pyrG expression and nucleotide pool sizes was quantified using metabolic control analysis in terms of inherent control coefficients. At the wild-type expression level, CTP synthase had full control of the CTP concentration with a concentration control coefficient close to one and a negative concentration control coefficient of ,0.28 for the UTP concentration. Additionally, a concentration control coefficient of 0.49 was calculated for the dCTP concentration. Implications for the homeostasis of nucleotide pools are discussed. [source] Oral vaccination of mice against Helicobacter pylori with recombinant Lactococcus lactis expressing urease subunit BFEMS IMMUNOLOGY & MEDICAL MICROBIOLOGY, Issue 3 2009Qing Gu Abstract To determine whether a protective immune response could be elicited by oral delivery of a recombinant live bacterial vaccine, Helicobacter pylori urease subunit B (UreB) was expressed for extracellular expression in food-grade bacterium Lactococcus lactis. The UreB-producing strains were then administered orally to mice, and the immune response to UreB was examined. Orally vaccinated mice produced a significant UreB-specific serum immunoglobulin G (IgG) response. Specific anti-UreB IgA responses could be detected in the feces of mice immunized with the secreting lactococcal strain. Mice vaccinated orally were significantly protected against gastric Helicobacter infection following a challenge with H. pylori strain SS1. In conclusion, mucosal vaccination with L. lactis expressing UreB produced serum IgG and UreB-specific fecal IgA, and prevented gastric infection with H. pylori. [source] A xylose-inducible expression system for Lactococcus lactisFEMS MICROBIOLOGY LETTERS, Issue 2 2004Anderson Miyoshi Abstract A new controlled production system to target heterologous proteins to cytoplasm or extracellular medium is described for Lactococcus lactis NCDO2118. It is based on the use of a xylose-inducible lactococcal promoter, PxylT. The capacities of this system to produce cytoplasmic and secreted proteins were tested using the Staphylococcus aureus nuclease gene (nuc) fused or not to the lactococcal Usp45 signal peptide. Xylose-inducible nuc expression is tightly controlled and resulted in high-level and long-term protein production, and correct targeting either to the cytoplasm or to the extracellular medium. Furthermore, this expression system is versatile and can be switched on or off easily by adding either xylose or glucose, respectively. These results confirm the potential of this expression system as an alternative and useful tool for the production of proteins of interest in L. lactis. [source] Heterologous gene expression in Lactococcus lactis; expression of the Azotobacter vinelandii algE6 gene product displaying mannuronan C-5 epimerase activityFEMS MICROBIOLOGY LETTERS, Issue 2 2003Janet M. Blatny Abstract The Azotobacter vinelandii mannuronan C-5 epimerases AlgE1,7 can be used to improve the properties of the commercially important polysaccharide alginate that is widely used in a variety of products, such as food and pharmaceuticals. Since lactic acid bacteria are generally regarded as safe, they are attractive candidates for production of the epimerases. A. vinelandii genes are GC-rich, in contrast to those of lactic acid bacteria, but we show here that significant expression levels of the epimerase AlgE6 can be obtained in Lactococcus lactis using the nisin-controlled expression system. A 1200-fold induction ratio was obtained resulting in an epimerase activity of 23,900 dpm mg,1 h,1, using a tritiated alginate substrate. The epimerase was detected by Western blotting and nuclear magnetic resonance spectroscopy analysis of its reaction product showed that the enzyme displayed catalytic properties similar to those produced in Escherichia coli. [source] Flavour formation by lactic acid bacteria and biochemical flavour profiling of cheese productsFEMS MICROBIOLOGY REVIEWS, Issue 3 2005Gerrit Smit Abstract Flavour development in dairy fermentations, most notably cheeses, results from a series of (bio)chemical processes in which the starter cultures provide the enzymes. Particularly the enzymatic degradation of proteins (caseins) leads to the formation of key-flavour components, which contribute to the sensory perception of dairy products. More specifically, caseins are degraded into peptides and amino acids and the latter are major precursors for volatile aroma compounds. In particular, the conversion of methionine, the aromatic and the branched-chain amino acids are crucial. A lot of research has focused on the degradation of caseins into peptides and free amino acids, and more recently, enzymes involved in the conversion of amino acids were identified. Most data are generated on Lactococcus lactis, which is the predominant organism in starter cultures used for cheese-making, but also Lactobacillus, Streptococcus, Propionibacterium and species used for surface ripening of cheeses are characterised in their flavour-forming capacity. In this paper, various enzymes and pathways involved in flavour formation will be highlighted and the impact of these findings for the development of industrial starter cultures will be discussed. [source] The long and winding road from the research laboratory to industrial applications of lactic acid bacteriaFEMS MICROBIOLOGY REVIEWS, Issue 3 2005Martin Bastian Pedersen Abstract Research innovations are constantly occurring in universities, research institutions and industrial research laboratories. These are reported in the scientific literature and presented to the scientific community in various congresses and symposia as well as through direct contacts and collaborations. Conversion of these research results to industrially useful innovations is, however, considerably more complex than generally appreciated. The long and winding road from the research laboratory to industrial applications will be illustrated with two recent examples from Chr. Hansen A/S: the implementation in industrial scale of a new production technology based on respiration by Lactococcus lactis and the introduction to the market of L. lactis strains constructed using recombinant DNA technology. [source] A tool kit for molecular genetics of Kluyveromyces lactis comprising a congenic strain series and a set of versatile vectorsFEMS YEAST RESEARCH, Issue 3 2010Jürgen J. Heinisch Abstract A set of different marker deletions starting with a ura3 derivative of the Kluyveromyces lactis type strain CBS2359 was constructed. After a first cross to obtain a strain with the opposite mating type that also carried a leu2 allele, continuous back-crosses were used to obtain a congenic strain series with different marker combinations, including deletions in KlHIS3, KlADE2 and KlLAC4. Enzymes involved in carbohydrate metabolism were shown to behave very similarly to the original type strain and other K. lactis strains investigated previously. Moreover, a vector series of Saccharomyces cerevisiae genes flanked by loxP sites was constructed to be used as heterologous deletion cassettes in K. lactis, together with two plasmids for expression of Cre-recombinase for marker regeneration. To increase the frequency of homologous recombination, the Klku80 deletion was also introduced into the congenic strain series. A PCR-based method for determination of mating type is provided. [source] Combined phylogenetic and neighbourhood analysis of the hexose transporters and glucose sensors in yeastsFEMS YEAST RESEARCH, Issue 4 2009Margarida Palma Abstract The sugar porter family in yeasts encompasses a wide variety of transporters including the hexose transporters and glucose sensors. We analysed a total of 75 members from both groups in nine hemiascomycetous species, with complete and well-annotated genomes: Saccharomyces cerevisiae, Candida glabrata, Zygosaccharomyces rouxii, Kluyveromyces thermotolerans, Saccharomyces kluyverii, Kluyveromyces lactis, Eremothecium gossypii, Debaryomyces hansenii and Yarrowia lipolytica. We present a model for the evolution of the hexose transporters and glucose sensors, supported by two types of complementary evidences: phylogeny and neighbourhood analysis. Five lineages of evolution were identified and discussed according to different mechanisms of gene evolution: lineage A for HXT1, HXT3, HXT4, HXT5, HXT6 and HXT7; lineage B for HXT2 and HXT10; lineage C for HXT8; lineage D for HXT14; and lineage E for SNF3 and RGT2. [source] Significance of the KlLAC1 gene in glucosylceramide production by Kluyveromyces lactisFEMS YEAST RESEARCH, Issue 6 2008Naoya Takakuwa Abstract Each of the 12 genes involved in the synthesis of glucosylceramide was overexpressed in cells of Kluyveromyces lactis to construct a strain accumulating a high quantity of glucosylceramide. Glucosylceramide was doubled by the KlLAC1 gene, which encodes ceramide synthase, and not by 11 other genes, including the KlLAG1 gene, a homologue of KlLAC1. Disruption of the KlLAC1 gene reduced the content below the detection level. Heterologous expression of the KlLAC1 gene in the cells of Saccharomyces cerevisiae caused the accumulation of ceramide, composed of C18 fatty acid. The KlLAC1 protein preferred long-chain (C18) fatty acids to very-long-chain (C26) fatty acids for condensation with sphingoid bases and seemed to supply a ceramide moiety as the substrate for the formation of glucosylceramide. When the amino acid sequences of ceramide synthase derived from eight yeast species were compared, LAC1 proteins from five species producing glucosylceramide were clearly discriminated from those of the other three species and all LAG1 proteins. The LAC1 protein of K. lactis is the enzyme that plays a crucial role in the synthesis of glucosylceramide. [source] Thematic issue on Kluyveromyces lactisFEMS YEAST RESEARCH, Issue 5 2007Hiroshi Fukuhara Guest Editor No abstract is available for this article. [source] Current status of Kluyveromyces systematicsFEMS YEAST RESEARCH, Issue 5 2007Marc-André Lachance Abstract A brief outline of the current taxonomic status of the genus Kluyveromyces is presented. Noteworthy are the transfer of several former Kluyveromyces species to other genera, the retention of the name Kluyveromyces for K. lactis, K. marxianus, and four related species, and some recent attempts to clarify the variety status of strains assigned to K. lactis. [source] KNQ1, a Kluyveromyces lactis gene encoding a transmembrane protein, may be involved in iron homeostasisFEMS YEAST RESEARCH, Issue 5 2007Emmanuela Marchi Abstract The original purpose of the experiments described in this article was to identify, in the biotechnologically important yeast Kluyveromyces lactis, gene(s) that are potentially involved in oxidative protein folding within the endoplasmic reticulum (ER), which often represents a bottleneck for heterologous protein production. Because treatment with the membrane-permeable reducing agent dithiothreitol inhibits disulfide bond formation and mimics the reducing effect that the normal transit of folding proteins has in the ER environment, the strategy was to search for genes that conferred higher levels of resistance to dithiothreitol when present in multiple copies. We identified a gene (KNQ1) encoding a drug efflux permease for several toxic compounds that in multiple copies conferred increased dithiothreitol resistance. However, the KNQ1 product is not involved in the excretion of dithiothreitol or in recombinant protein secretion. We generated a knq1 null mutant, and showed that both overexpression and deletion of the KNQ1 gene resulted in increased resistance to dithiothreitol. KNQ1 amplification and deletion resulted in enhanced transcription of iron transport genes, suggesting, for the membrane-associated protein Knq1p, a new, unexpected role in iron homeostasis on which dithiothreitol tolerance may depend. [source] A respiratory-deficient mutation associated with high salt sensitivity in Kluyveromyces lactisFEMS YEAST RESEARCH, Issue 2 2007Paola Goffrini Abstract A salt-sensitive mutant of Kluyveromyces lactis was isolated that was unable to grow in high-salt media. This mutant was also respiratory-deficient and temperature-sensitive for growth. The mutation mapped in a single nuclear gene that is the ortholog of BCS1 of Saccharomyces cerevisiae. The BCS1 product is a mitochondrial protein required for the assembly of respiratory complex III. The bcs1 mutation of S. cerevisiae leads to a loss of respiration, but, unlike in K. lactis, it is not accompanied by salt sensitivity. All the respiratory-deficient K. lactis mutants tested were found to be salt-sensitive compared to their isogenic wild-type strains. In the presence of the respiratory inhibitor antimycin A, the wild-type strain also became salt-sensitive. By contrast, none of the S. cerevisiae respiratory-deficient mutants tested showed increased salt sensitivity. The salt sensitivity of the Klbcs1 mutant, but not its respiratory deficiency, was suppressed by the multicopy KlVMA13 gene, a homolog of the S. cerevisiae VMA13 gene encoding a subunit of the vacuolar H+ -ATPase. These results suggest that cellular salt homeostasis in K. lactis is strongly dependent on mitochondrial respiratory activity, and/or that the ion homeostasis of mitochondria themselves could be a primary target of salt stress. [source] KlADH3, a gene encoding a mitochondrial alcohol dehydrogenase, affects respiratory metabolism and cytochrome content in Kluyveromyces lactisFEMS YEAST RESEARCH, Issue 8 2006Michele Saliola Abstract A Kluyveromyces lactis strain, harbouring KlADH3 as the unique alcohol dehydrogenase (ADH) gene, was used in a genetic screen on allyl alcohol to isolate mutants deregulated in the expression of this gene. Here we report the characterization of some mutants that lacked or had highly reduced amounts of KlAdh3p activity; in addition, these mutants showed alterations in glucose metabolism, reduced respiration and reduced cytochrome content. Our results confirm that the KlAdh3p activity contributes to the reoxidation of cytosolic NAD(P)H feeding the respiratory chain through KlNdi1p, the mitochondrial internal transdehydrogenase. The low levels of KlAdh3p in two of the mutants were associated with mutations in KlSDH1, one of the genes of complex II, suggesting signalling between the respiratory chain and expression of the KlADH3 gene. [source] Thematic issue on Kluyveromyces lactisFEMS YEAST RESEARCH, Issue 3 2006Ángel Domínguez Olavarri No abstract is available for this article. [source] Kluyveromyces lactis, a retrospectiveFEMS YEAST RESEARCH, Issue 3 2006Hiroshi Fukuhara No abstract is available for this article. [source] Why does Kluyveromyces lactis not grow under anaerobic conditions?FEMS YEAST RESEARCH, Issue 3 2006Comparison of essential anaerobic genes of Saccharomyces cerevisiae with the Kluyveromyces lactis genome Abstract Although some yeast species, e.g. Saccharomyces cerevisiae, can grow under anaerobic conditions, Kluyveromyces lactis cannot. In a systematic study, we have determined which S. cerevisiae genes are required for growth without oxygen. This has been done by using the yeast deletion library. Both aerobically essential and nonessential genes have been tested for their necessity for anaerobic growth. Upon comparison of the K. lactis genome with the genes found to be anaerobically important in S. cerevisiae, which yielded 20 genes that are missing in K. lactis, we hypothesize that lack of import of sterols might be one of the more important reasons that K. lactis cannot grow in the absence of oxygen. [source] The Kluyver effect revisitedFEMS YEAST RESEARCH, Issue 4 2003Hiroshi Fukuhara Abstract Yeast species can grow on various sugars. However, in many cases the growth on certain sugars (especially oligosaccharides) occurs only under aerobic conditions, and not in anaerobiosis or in the absence of respiration. Fermentation is blocked under these conditions. This apparent dependence of sugar utilization on the respiration has been called Kluyver effect, and such ,respiration-dependent' species are called Kluyver effect positive. A yeast may be Kluyver effect positive for some sugars and not for others. The physiological meaning and the molecular basis of the phenomenon are not clear. It has recently been reported that Kluyveromyces lactis, which is Kluyver effect positive for galactose and a few other sugars, could be converted into a Kluyver effect-negative form by introduction of relevant sugar transporter genes. Such results offer for the first time a direct support to the hypothesis that the immediate cause of the Kluyver effect may be the low level of sugar transporter activities which is not sufficient to sustain the high substrate flow necessary for fermentative growth, whereas the energy-efficient respiratory growth does not require a high rate of sugar uptake. We examined to what extent this sugar transporter theory of the Kluyver effect can be generalized. [source] Investigation of the Immunomodulatory Effects of Lactobacillus casei and Bifidobacterium lactis on Helicobacter pylori InfectionHELICOBACTER, Issue 3 2008Li Zhang Abstract Background:,Lactobacillus and Bifidobacterium species have shown beneficial effects in the treatment of Helicobacter pylori infection; however, the mechanisms behind such effects are not fully understood. In this study, we have investigated the immunomodulatory effects of probiotics in a mouse model of H. pylori infection. Materials and methods:,H. pylori -infected C57BL/6 mice were treated with L. casei L26, B. lactis B94, or no probiotics for 5 weeks, respectively. Mice not infected with H. pylori were included as normal controls. Gastric histology, protein levels of interleukin (IL)-1,, IL-10, IL-12/23p40, and H. pylori colonization density in the gastric tissues, as well as H. pylori -specific antibodies were examined. Results:, In mice receiving L. casei L26 and B. lactis B94, gastric neutrophil infiltration and IL-1, were significantly decreased and IL-10 was significantly increased as compared with mice receiving no probiotics. In mice receiving B. lactis B94, IL-12/23p40 was significantly increased and H. pylori IgG was significantly reduced as compared with mice receiving no probiotics. No significant difference of H. pylori colonization was observed among the three groups of mice. Conclusion:, The reduced level of IL-1, and neutrophil infiltration observed in mice infected with H. pylori following treatment with L. casei L26 and B. lactis B94 resulted from a modulation of immune response rather than a decrease of H. pylori colonization. Furthermore, B. lactis B94 has the intrinsic ability to promote a Th1 immune response through an increase in IL-12/IL-23. [source] Bifidobacterium lactis inhibits NF-,B in intestinal epithelial cells and prevents acute colitis and colitis-associated colon cancer in mice,,INFLAMMATORY BOWEL DISEASES, Issue 9 2010Seung Won Kim MS Abstract Background: The aim of this study was to investigate the antiinflammatory effects of Bifidobacterium lactis on intestinal epithelial cells (IECs) and on experimental acute murine colitis and its tumor prevention effects on colitis-associated cancer (CAC) in mice. Methods: Human HT-29 cells were stimulated with IL-1,, lipopolysaccharides, or tumor necrosis factor-, with and without B. lactis, and the effects of B. lactis on nuclear factor kappa B (NF-,B) signaling in IEC were examined. For in vivo study, dextran sulfate sodium (DSS)-treated mice were fed with and without B. lactis. Finally, we induced colonic tumors in mice by azoxymethane (AOM) and DSS and evaluated the effects of B. lactis on tumor growth. Results: B. lactis significantly suppressed NF-,B activation, including NF-,B-binding activity and NF-,B-dependent reporter gene expression in a dose-dependent manner, and suppressed I,B-, degradation, which correlated with the downregulation of NF-,B-dependent gene products. Moreover, B. lactis suppressed the development of acute colitis in mice. Compared with the DSS group, the severity of DSS-induced colitis as assessed by disease activity index, colon length, and histological score was reduced in the B. lactis -treated group. In the CAC model, the mean number and size of tumors in the B. lactis -treated group were significantly lower than those in the AOM group. Conclusions: Our data demonstrate that B. lactis inhibits NF-,B and NF-,B-regulated genes in IEC and prevents acute colitis and CAC in mice. These results suggest that B. lactis could be a potential preventive agent for CAC as well as a therapeutic agent for inflammatory bowel disease. (Inflamm Bowel Dis 2010) [source] Screening for natural defence mechanisms of Lactococcus lactis strains isolated from traditional starter culturesINTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 7 2007Andreja Mikli Summary Three different bacterial defence mechanisms were identified in the seventeen Lactococcus lactis isolates from starter cultures in three Slovenian dairy plants. Isolates MB18, KR7, PT4, PT13 and PT19 inhibited phage adsorption by means of exopolysaccharides production. The most extensive polysaccharides production was detected in PT19 isolate, which was susceptible only to phage ,PT19. Eight isolates exhibited nuclease activity, and seven of them were susceptible up to four phages out of thirteen from our collection. Eight isolates possessed the abiB gene, fourteen isolates abiH, two isolates abiJ and one isolate abiQ. Isolates PT27 and PT28 possessed AbiB, AbiH and AbiJ mechanisms as well as inhibition of phage adsorption. Isolate MB18, which was susceptible to one phage only, possessed the abiQ gene, nuclease activity and ability to prevent adsorption of most phages. Isolates PT67 and PT70, possessing only AbiH mechanism, were susceptible to only two phages. [source] Chemical and microbiological quality of Garris, Sudanese fermented camel's milk productINTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 3 2006Abdel Moneim El-Hadi Sulieman Summary In the present study, some of the chemical and microbiological characteristics of garris, a Sudanese traditionally fermented camel's milk product, were investigated. The chemical analyses included, pH, titrable acidity and ethanol contents. A total of 100 strains of lactic acid bacteria (LAB) were isolated from twenty samples of traditionally fermented household garris. The selected isolates were phenotypically characterized by their ability to ferment 49 carbohydrates using API 50 CHL kits and additional biochemical tests. LAB dominated the microflora of garris samples, and the major genera were Lactobacillus (74%), followed by Lactococcus (12%), Enterococcus (10%) and Leuconostocs (4%). The most predominant Lactobacillus species were identified as Lactobacillus paracasei ssp. paracasei (64 strains), L. fermentum (seven strains) and only three strains as L. plantarum. Most strains produced the enzymes that are relevant to cultured dairy product processing. The Lactococcus species were identified as Lactococcus lactis. The average pH value of the samples was 4.42 ± 0.21. The pH values were accompanied with increasing of titrable acidity which averaged 1.72 ± 0.04%. The relatively high amounts of ethanol detected in all samples (average 1.40 ± 0.03%) together with the high yeasts counts (6.0 ± 0.53 log10 cfu mL,1), indicated that the fermentation process of garris is a yeast-lactic fermentation. [source] Genotypic and technological characterization of Lactococcus lactis isolates involved in processing of artisanal Manchego cheeseJOURNAL OF APPLIED MICROBIOLOGY, Issue 5 2009P. Nieto-Arribas Abstract Aims:, Genotypic and technological characterization of wild lactococci isolated from artisanal Manchego cheese during the ripening process for selection of suitable starter cultures. Methods and Results:, A total of 114 isolates of lactococci were typed using randomly amplified polymorphic DNA-polymerase chain reaction (RAPD-PCR). Sixteen distinct RAPD-PCR patterns, at a similarity level of 73%, were obtained. On the basis of species-specific PCR reaction, the isolates were assigned to the species Lactococcus lactis subsp. lactis and Lactococcus lactis subsp. cremoris with L. lactis subsp. lactis being predominant at both dairies. Twenty-six isolates were technologically characterized to select those with the best properties. Most of them showed good technological properties although some could produce tyramine. Conclusions:, The presence of coincident genotypes at both dairies has been demonstrated, which would suggest that they are well adapted to the Manchego cheese environment. Interesting differences were found in the technological characterization and the potential role of autochthonous lactococci strains as starter culture has been displayed. Significance and Impact of the Study:, The great economic importance of Manchego cheese encouraged a deeper knowledge of its microbiota, to select strains with the best properties to use as starter cultures in industrial Manchego cheeses, preserving the autochthonous characteristics. [source] Use of induction promoters to regulate hyaluronan synthase and UDP-glucose-6-dehydrogenase of Streptococcus zooepidemicus expression in Lactococcus lactis: a case study of the regulation mechanism of hyaluronic acid polymerJOURNAL OF APPLIED MICROBIOLOGY, Issue 1 2009J.Z. Sheng Abstract Aims:, To determine the effects of the ratios of hyaluronan synthase expression level to precursor sugar UDP-GlcA biosynthesis ability on the molecular weight (MW) of hyaluronic acid (HA) in recombinant Lactococcus lactis. Methods and Results:, The genes szHasA (hyaluronan synthase gene) and szHasB (UDP-glucose-6-dehydrogenase gene) of Streptococcus zooepidemicus were introduced into L. lactis under the control of nisA promoter and lacA promoter respectively, resulting in a dual-plasmid controlled expression system. The effects of the ratios of hyaluronan synthase expression level to the precursor sugar UDP-GlcA biosynthesis ability under different induction concentration collocations with nisin and lactose on the MW of HA in recombinant L. lactis were determined. The results showed that the final weight-average molecular weight () of HA correlated with the relative ratios of HasA (hyaluronan synthase) expression level to the concentration of UDP-GlcA. Conclusions:, Regulating the relative ratios of HasA expression level to the precursor sugar biosynthesis ability was an efficient method to control the size of HA. Significance and Impact of the Study:, This study put forward a guide to establish an efficacious way to control the size of HA in fermentation. [source] | |||||||||||||||||||||||||||||||