During infection, Staphylococcus aureus is exposed to exogenous menaquinone which is essential for the human blood clotting cascade. The effect of exogenous menaquinone on S. aureus phenotypic expression is not known....During infection, Staphylococcus aureus is exposed to exogenous menaquinone which is essential for the human blood clotting cascade. The effect of exogenous menaquinone on S. aureus phenotypic expression is not known. To test whether menaquinone affects expression of virulence-associated phenotypes, methicillin-sensitive (MSSA) and -resistant (MRSA) S. aureus strains (n = 8) were grown in the presence of menaquinone (0.001 - 12 μg/ml). Capsule production, biofilm formation (plastic and fibronectin-coated microtiter plates) and carotenoid levels were determined spectrophotometrically after growth in Mueller Hinton broth (MH;24-hr, 37°C). All experiments were, at minimum, done in triplicate and repeated twice. Menaquinone at physiologic levels (0.01 μg/ml MH) significantly increased (p 0.05) biofilm formation on plastic in a manner that was bacterial population size dependent. In addition, menaquinone (0.05 - 4 μg/ml) significantly increased (p 0.05) biofilm formation on fibronectin-coated surfaces for four MSSA strains and one MRSA strain by two to six-fold as compared to medium controls. However, menaquinone had no effect on capsule production or cell-associated carotenoid levels. Menaquinone’s effect on biofilm formation on fibronectin-coated surfaces appears to be regulated by sarA. These findings are the first to demonstrate that a vitamin at concentrations reported in humans affects S. aureus virulence-associated phenotypes.展开更多
BACKGROUND Helicobacter pylori(H.pylori)infection is closely associated with gastrointestinal diseases.Our preliminary studies have indicated that H.pylori infection had a significant impact on the mucosal microbiome ...BACKGROUND Helicobacter pylori(H.pylori)infection is closely associated with gastrointestinal diseases.Our preliminary studies have indicated that H.pylori infection had a significant impact on the mucosal microbiome structure in patients with gastric ulcer(GU)or duodenal ulcer(DU).AIM To investigate the contributions of H.pylori infection and the mucosal microbiome to the pathogenesis and progression of ulcerative diseases.METHODS Patients with H.pylori infection and either GU or DU,and healthy individuals without H.pylori infection were included.Gastric or duodenal mucosal samples was obtained and subjected to metagenomic sequencing.The compositions of the microbial communities and their metabolic functions in the mucosal tissues were analyzed.RESULTS Compared with that in the healthy individuals,the gastric mucosal microbiota in the H.pylori-positive patients with GU was dominated by H.pylori,with signi-ficantly reduced biodiversity.The intergroup differential functions,which were enriched in the H.pylori-positive GU patients,were all derived from H.pylori,particularly those concerning transfer RNA queuosine-modification and the synthesis of demethylmenaquinones or menaquinones.A significant enrichment of the uibE gene was detected in the synthesis pathway.There was no significant difference in microbial diversity between the H.pylori-positive DU patients and healthy controls.CONCLUSION H.pylori infection significantly alters the gastric microbiota structure,diversity,and biological functions,which may be important contributing factors for GU.展开更多
The majority of bacterial infections involve the formation of biofilms. Biofilm formation is nutrient and growth dependent. Determination of the effects of nutrients on exopolysaccharide production and bacterial growt...The majority of bacterial infections involve the formation of biofilms. Biofilm formation is nutrient and growth dependent. Determination of the effects of nutrients on exopolysaccharide production and bacterial growth is labor and time intensive. We tested whether the Bioscreen C (Growth Curves, Inc.) would have utility as a high-throughput tool in the measurement of fundamental phenotype expression, as it relates to growth conditions. Within 48 - 72 hr, reproduceble, statistically significant data on the affects of growth conditions on generation time, capsule production and biofilm formation (maximally for 25 different conditions per 24 hr run cycle;n = 4) were obtained. Although all S. aureus strains produced similar amounts of capsule, sarA– and agr– strains grew significantly slower than parent strain (1.6 fold slower) and produced significantly (p 0.05) less biofilm (~2 fold). E. coli growth rate, biofilm and capsule production in simulated nephropathic urine medium was similar for urine with insulin (20 μU). Addition of insulin to urine medium with proline increased generation time, capsule and biofilm production. Findings from this study show that the Bioscreen C is a rapid, reproducible, and easily manipulated system to concurrently measure bacterial growth, biofilm formation, and capsule production. In addition, there is the potential for further applications of this system by expanding the types of detector dyes used.展开更多
The semiempirical AMI method, ah initio (HF/3-21G, 6-31G, 6-31G(d), 6-31+G(d)) and DFT (B3LYP/6-31G(d), 6-31+G(d)) methods were used to optimize the geometry of DDQ and its anion radical DDQ-. Nelsen’s model was used...The semiempirical AMI method, ah initio (HF/3-21G, 6-31G, 6-31G(d), 6-31+G(d)) and DFT (B3LYP/6-31G(d), 6-31+G(d)) methods were used to optimize the geometry of DDQ and its anion radical DDQ-. Nelsen’s model was used to calculate the internal reorganization energy λi of self-exchange electron transfer (ET) reactions. The calculated λi results of DDQ/DDQ-. by AM1 and B3LYP/ 6-31G(d), 6-31+G(d) methods are close to each other and consistent with the reported values; while those from Har-tree-Fock methods are too large because of not consideringthe effect of electron correlation. The structure and ET behavior of MQ0 /MQ0- couple were studied by AM1 and DFT (B3LYP/6-31G(d), 6-31+ G(d, p)) methods, and those of MQ0 /MQn-(n=1-7) were studied by AM1 method for the first time. The results indicate that the values of the heat of formation of MQn increases with the increasing of the length of the isoamylene substituent chains. It also shows that the length of substituent has little effect on the bond lengths,展开更多
The gene product Sll1127 is a predicted 1,4-dihydroxy-2-naphthoyl-CoA synthase catalyzing an intramolecular Claisen condensation in the phylloquinone biosynthesis of the cyanobacterium Synechocystis sp.PCC 6803.This p...The gene product Sll1127 is a predicted 1,4-dihydroxy-2-naphthoyl-CoA synthase catalyzing an intramolecular Claisen condensation in the phylloquinone biosynthesis of the cyanobacterium Synechocystis sp.PCC 6803.This predicted catalytic function has been verified and the enzyme has been characterized for the first time with kcat = 0.013 s-1 and KM = 9μM.Its catalytic activity is found to strictly depend on externally added bicarbonate with an apparent KD = 0.60 mM.In addition,this enzyme is inhibited by its 1,4-dihydroxy-2-naphthoyl-CoA product through high-affinity binding,which causes a 18 nm shift of the inhibitor absorption at 392 to 410 nm and engenders a new absorption peak at 345 nm.All these properties of the cyanobacterial enzyme are closely similar to those of the Escherichia coli orthologue from the menaquinone biosynthetic pathway.These results provide additional supporting evidence for the essential role of bicarbonate as a catalytic base in the enzymatic reaction and the eubacterial origin of the enzymes in the cyanobacterial biosynthesis of phylloquinone.展开更多
文摘During infection, Staphylococcus aureus is exposed to exogenous menaquinone which is essential for the human blood clotting cascade. The effect of exogenous menaquinone on S. aureus phenotypic expression is not known. To test whether menaquinone affects expression of virulence-associated phenotypes, methicillin-sensitive (MSSA) and -resistant (MRSA) S. aureus strains (n = 8) were grown in the presence of menaquinone (0.001 - 12 μg/ml). Capsule production, biofilm formation (plastic and fibronectin-coated microtiter plates) and carotenoid levels were determined spectrophotometrically after growth in Mueller Hinton broth (MH;24-hr, 37°C). All experiments were, at minimum, done in triplicate and repeated twice. Menaquinone at physiologic levels (0.01 μg/ml MH) significantly increased (p 0.05) biofilm formation on plastic in a manner that was bacterial population size dependent. In addition, menaquinone (0.05 - 4 μg/ml) significantly increased (p 0.05) biofilm formation on fibronectin-coated surfaces for four MSSA strains and one MRSA strain by two to six-fold as compared to medium controls. However, menaquinone had no effect on capsule production or cell-associated carotenoid levels. Menaquinone’s effect on biofilm formation on fibronectin-coated surfaces appears to be regulated by sarA. These findings are the first to demonstrate that a vitamin at concentrations reported in humans affects S. aureus virulence-associated phenotypes.
基金Supported by Wenling Science and Technology Program,China,No.2020S0180101Science and Technology Program of Traditional Chinese Medicine in Zhejiang Province,China,No.2023ZL784.
文摘BACKGROUND Helicobacter pylori(H.pylori)infection is closely associated with gastrointestinal diseases.Our preliminary studies have indicated that H.pylori infection had a significant impact on the mucosal microbiome structure in patients with gastric ulcer(GU)or duodenal ulcer(DU).AIM To investigate the contributions of H.pylori infection and the mucosal microbiome to the pathogenesis and progression of ulcerative diseases.METHODS Patients with H.pylori infection and either GU or DU,and healthy individuals without H.pylori infection were included.Gastric or duodenal mucosal samples was obtained and subjected to metagenomic sequencing.The compositions of the microbial communities and their metabolic functions in the mucosal tissues were analyzed.RESULTS Compared with that in the healthy individuals,the gastric mucosal microbiota in the H.pylori-positive patients with GU was dominated by H.pylori,with signi-ficantly reduced biodiversity.The intergroup differential functions,which were enriched in the H.pylori-positive GU patients,were all derived from H.pylori,particularly those concerning transfer RNA queuosine-modification and the synthesis of demethylmenaquinones or menaquinones.A significant enrichment of the uibE gene was detected in the synthesis pathway.There was no significant difference in microbial diversity between the H.pylori-positive DU patients and healthy controls.CONCLUSION H.pylori infection significantly alters the gastric microbiota structure,diversity,and biological functions,which may be important contributing factors for GU.
文摘The majority of bacterial infections involve the formation of biofilms. Biofilm formation is nutrient and growth dependent. Determination of the effects of nutrients on exopolysaccharide production and bacterial growth is labor and time intensive. We tested whether the Bioscreen C (Growth Curves, Inc.) would have utility as a high-throughput tool in the measurement of fundamental phenotype expression, as it relates to growth conditions. Within 48 - 72 hr, reproduceble, statistically significant data on the affects of growth conditions on generation time, capsule production and biofilm formation (maximally for 25 different conditions per 24 hr run cycle;n = 4) were obtained. Although all S. aureus strains produced similar amounts of capsule, sarA– and agr– strains grew significantly slower than parent strain (1.6 fold slower) and produced significantly (p 0.05) less biofilm (~2 fold). E. coli growth rate, biofilm and capsule production in simulated nephropathic urine medium was similar for urine with insulin (20 μU). Addition of insulin to urine medium with proline increased generation time, capsule and biofilm production. Findings from this study show that the Bioscreen C is a rapid, reproducible, and easily manipulated system to concurrently measure bacterial growth, biofilm formation, and capsule production. In addition, there is the potential for further applications of this system by expanding the types of detector dyes used.
基金This work was supportedby the National Natural Science Foundation of China (Grant Nos. 29733100 and 39890390) and the State Key Basic Research and Development Plan (Grant No. G1998010100).
文摘The semiempirical AMI method, ah initio (HF/3-21G, 6-31G, 6-31G(d), 6-31+G(d)) and DFT (B3LYP/6-31G(d), 6-31+G(d)) methods were used to optimize the geometry of DDQ and its anion radical DDQ-. Nelsen’s model was used to calculate the internal reorganization energy λi of self-exchange electron transfer (ET) reactions. The calculated λi results of DDQ/DDQ-. by AM1 and B3LYP/ 6-31G(d), 6-31+G(d) methods are close to each other and consistent with the reported values; while those from Har-tree-Fock methods are too large because of not consideringthe effect of electron correlation. The structure and ET behavior of MQ0 /MQ0- couple were studied by AM1 and DFT (B3LYP/6-31G(d), 6-31+ G(d, p)) methods, and those of MQ0 /MQn-(n=1-7) were studied by AM1 method for the first time. The results indicate that the values of the heat of formation of MQn increases with the increasing of the length of the isoamylene substituent chains. It also shows that the length of substituent has little effect on the bond lengths,
基金supported by GRF601209 from the Research Grants Council of the HKSAR government
文摘The gene product Sll1127 is a predicted 1,4-dihydroxy-2-naphthoyl-CoA synthase catalyzing an intramolecular Claisen condensation in the phylloquinone biosynthesis of the cyanobacterium Synechocystis sp.PCC 6803.This predicted catalytic function has been verified and the enzyme has been characterized for the first time with kcat = 0.013 s-1 and KM = 9μM.Its catalytic activity is found to strictly depend on externally added bicarbonate with an apparent KD = 0.60 mM.In addition,this enzyme is inhibited by its 1,4-dihydroxy-2-naphthoyl-CoA product through high-affinity binding,which causes a 18 nm shift of the inhibitor absorption at 392 to 410 nm and engenders a new absorption peak at 345 nm.All these properties of the cyanobacterial enzyme are closely similar to those of the Escherichia coli orthologue from the menaquinone biosynthetic pathway.These results provide additional supporting evidence for the essential role of bicarbonate as a catalytic base in the enzymatic reaction and the eubacterial origin of the enzymes in the cyanobacterial biosynthesis of phylloquinone.
