Study on Antibacterial Activity of 2-Methyl-3-(methylthio)Pyrazine Against Three Strains of Spoilage Bacteria

Previous studies have shown that glycine and proline are pharmacophores that display antibacterial activity.In the present study,glycine and proline were derivated to diketopiperazine compounds by chemical synthesis method,and their antibacterial activities were evaluated by three strains of spoilage bacteria,Escherichia coli,Pseudomonas aeruginosa and Shewanella putrefaciens,and the relationship of their antibacterial activities and structures was also investigated.Uv-vis spectrophotometry was used to determine the growth curves of three kinds of active indicator bacteria.Minimum inhibitory concentration(MIC)was determined by micro broth dilution method.The results showed that 2-methyl-3-(methylthio)pyrazine had significant antibacterial activity against three strains of the bacteria,and its MIC was 1.25%.It indicates 2-methyl-3-(methylthio)pyrazine has the potential to be developed as a kind of preservative in future.

Zinc Oxide Nanoparticles in Bacterial Growth Medium: Optimized Dispersion and Growth Inhibition of <i>Pseudomonas putida</i>

The majority of nanoparticles tend to agglomerate in bacterial growth media. Thus, nanoparticle-specific characteristics can get lost. To investigate the influence of nanoparticles on bacteria, these particles should remain in their nanoparticulate state. The present study demonstrates the stabilization of commercially available zinc oxide (ZnO) with sodiumhexametaphosphate (SHMP) in bacterial growth medium (LB) to avoid agglomeration of these particles after the addition to LB. This established method is appropriate to stabilize ZnO agglomerates as small as 43 nm. The method of fractionated centrifugation was used to obtain stable agglomerates (also stable in the presence of bacteria) with different mean diameters. The SHMP-stabilized ZnO inhibits the growth of Pseudomonas putida with increasing concentration (up to 500 mg/L) and decreasing agglomerate size (43 - 450 nm).

EPIDERMAL GROWTH FACTOR PREVENTS INCREASED PERMEABILITY AND BACTERIAL TRANSLOCATION IN RATS WITH ACUTE PANCREATITIS

To evaluate the effects of epidermal growth factor (EGF) on intestinal permeability and bacterial translocation in rats with acute pancreatitis during total parenteral nutrition (TPN). Methods. Thirty- two male Sprague- Dawley rats that underwent injection of 3.5％ sodium taurocholate solution into the pancreatic duct were randomly divided into one of the following two groups: (1) received only TPN (control group) or (2) received TPN with EGF at a dose of 0.2 mg· kg- 1· day- 1 (Egf group). On fifth day of total parenteral nutrition, samples from mesenteric lymph nodes, pancreas, liver and spleen were harvested for cultures. Water, protein and DNA content in jejunal mucosa were determined. D- xylose and fluorescein isothiocyanate (FITC)- dextran were instilled into the lumen of a ligated segament of small intestine. Thirty minutes later, superior mesenteric vein D- xylose and plasma FITC- dextran concentration were measured. Results. Positive cultures in liver and spleen, as well as FITC- dextran concentration in the Egf group were significantly lower than in the control group. Protein and DNA content in jejunal mucosa in the Egf group were significantly higher than in the control group. Conclusion. The results indicate that EGF may prevent increased intestinal permeability and bacterial translocation in rats with acute pancreatitis during TPN.

Testing of Bacterial Endophytes from Non-Host Sources as Potential Antagonistic Agents against Tomato Wilt Pathogen <i>Ralstonia solanacearum</i>

The study was taken up with the objective of testing whether the endophytic organisms isolated from crops that are normally non-hosts to the bacterial wilt pathogen Ralstonia solanacearum possessed pathogen-antagonistic activity and to evaluate the selected isolates for the alleviation of wilt disease in the target tomato crop through horizontal movement of promising organisms. Sixteen endophytic bacteria (EB) isolated from the micropropagated cultures of grape, watermelon and papaya were tested for potential antagonistic effects against R. solanacearum tomato isolate “NH-01” through agar-well diffusion assay. Enterobacter cloacae from papaya (EB-11) displayed the maximum antagonistic effect followed by Bacillus subtilis (EB-06) and B. flexus (EB-07) from watermelon and B. pumilus (EB-02) from grape. Testing the above organisms for crop protection through seed fortification of susceptible tomato cv. Arka Vikas at sowing in R. solanacearum inoculated (Ral+) organic cocopeat showed EB-02 and EB-11 promising (33% and 32% survival, respectively, four weeks after sowing against 15% in Ral+ control). A second trial showed 37%, 28%, 21% and 55% seedling survival 6 weeks after sowing for EB-02, EB-06, EB-07 and EB-11 respectively, compared to 2.5% in non-treated control. Assessing the four endophytes for crop protection in Ral+ sick-soil through seedling fortification at transplanting indicated less disease incidence in treated sets (40%, 40%, 20% and 20% survival, respectively, six weeks after transplanting) over non-fortified control (5%). Endophytic fortification of seedlings through hypocotyl inoculation showed some systemic resistance induction upon seedling transplanting to sick soil but not with petiole fortification. Seedling growth was enhanced by the isolates EB-06 and EB-07. The study thus identifies four endophytic organisms from crops unrelated to tomato possessing potential antagonistic activity against the wilt pathogen and prospects for exploitation as biocontrol agents coupled with seedling growth promotion effects.

Magnesium improves hydrogen production by a novel fermentative hydrogen-producing bacterial strain B49

Batch experiments were conducted to investigate the effects of magnesium on glucose metabolism, including growth and hydrogen-producing capacity of fermentative hydrogen-producing bacterial strain B49. These abilities were enhanced with an increase in magnesium concentration. At the end of fermentation from （10 g/L） glucose, for 10 mg/L MgCl2·6H2O the cell growth in terms of optical density （OD） at 600nm was 0.46, the ratio of ethanol amount （mg/L） to acetate amount （mg/L） was 1.1, and the accumulated hydrogen volume was 934.9 mL H2/L culture; for 200 mg/L of MgCl2·6H2O OD600 nm was increased to 1.34. The accumulated hydrogen volume was increased to 2 360.5 mL H2/L culture, the ratio of ethanol amount （mg/L） to acetate amount （mg/L） was increased to 1.3 and polysaccharide was decreased to 2.5 mg/L. Moreover, the magnesium solution addition to the medium at different fermentation times affected hydrogen-producing ability. However, the later the addition time was postponed, the less the effect was on hydrogen evolution. Further experiments confirmed the enhancement was dependent on magnesium ions and not on the other inorganic ions such as SO42- or Cl-, which constituted the magnesium salts.

Rhizosphere Bacteria for Biocontrol of Bacterial Blight and Growth Promotion of Rice

Several bacterial strains were isolated from different rhizospheres. Among these, strain PDY7 exhibited strong antibacterial activity against the rice bacterial blight （BB） pathogen Xanthomonas oryzae pv. oryzae （Xoo） by the laboratory dual plate assays. The antibacterial property of the strain PDY7 was further investigated for the production of 2,4-diacetylphloroglucinol （DAPG）, which amplified a characteristic of 629-bp DNA fragment by PCR-based screening method using phlD primers. The application of phlD positive strains was carefully evaluated for disease control and growth promotion of rice plants under field conditions. The selected strain PDY7 suppressed the rice BB by 58.83% and 51.88% under glass house and field conditions, respectively. In addition, the strain PDY7 showed significant two-fold increase in root length （18.08 cm）, shoot length （29.81 cm）, and grain yield （96.07 g）. Strain PDY7 promoted the growth of rice plants by production of indole-3-acetic acid （IAA）, which was determined by high performance liquid chromatography （HPLC） analysis. Our findings suggest that PDY7 belongs to the P. fluorescens group and can serve as potential biocontrol of BB as well as biofertilizer agent for growth promotion of rice.

Bacterial communities fluctuate in abundance and diversity under simulated oil-contaminated seawater conditions

Marine bacteria have recently been identified as a potent solution for petroleum hydrocarbon degradation in response to hazardous oceanic oil spills. In this study, a mesocosm experiment simulating a petroleum spill event was performed to investigate changes in the abundance, structure, and productivity of bacterial communities in response to oil pollution. Cultured heterotrophic bacteria and total bacteria showed a consistent trend involving an immediate decrease in abundance, followed by a slight increase, and a steady low-level thereafter. However, the changing trend of bacterial productivity based on bacterial biomass and bacterial volume showed the opposite trend. In addition, the density of oil-degrading bacteria increased initially, then subsequently declined. The change in the bacterial community structure at day 0 and day 28 were also analyzed by amplified ribosomal DNA restriction analysis (ARDRA), which indicated that the species diversity of the bacterial community changed greatly after oil pollution. Alphaproteobacteria (40.98%) replaced Epsilonproteobacteria (51.10%) as the most abundant class, and Gammaproteobacteria (38.80%) became the second most dominant class in the whole bacterial community. The bacterial communities in oil-contaminated seawater (32 genera) became much more complex than those found in the natural seawater sample (16 genera). The proportion of petroleum-degrading bacteria in the oil-contaminated seawater also increased. In this study, culture-dependent and culture-independent approaches were combined to elucidate changes in both bacterial productivity and community structure. These findings will contribute to a better understanding of the role that bacteria play in material cycling and degradation in response to oil pollution.

A Study of Bacterial Linear Growth Using A Microcalorimetric Method

By using an LKB-2277 bioactivity monitor, we have determined the thermogenesis curves of four kinds of anaerobes linear growth. From the thermogenesis curves, we established the growth thermokinetic equation:dp/dt = km Pn,the order of growth metabolism n=0, and calculated the mean specific rate constant of multiplication μ. It is a new kind of bacterial growth,it was compared with exponential growth.

Growth Responses of Some Bacterial Isolates to Some Environmental Parameters

This study was carried out to investigate the antimicrobial activities of bacterial isolates of maize against plant pathogens as well as their growth responses to some environmental parameters. Twenty four bacterial isolates were obtained from maize plants collected from the Department of Biological Sciences, AfeBabalola University, Ado-Ekiti. The isolates were characterized by their biochemical and physiological characteristics and were identified as Kurthiazopfu, Morganellamorganic, Rhodococcusequi, Bacillus subtilis, Catabaterhongkongensis, Brevibacteriumotitidis, Lactobacillus coleohominis, Staphylococcus aureus, Propionibacterium acnes among others. Their responses to different NaCl concentrations, sugars, temperature as well as antibiotics were determined. Most of the isolates were able to withstand various environmental parameters in which they were subjected to. Also, eight isolates were able to ferment sucrose. The bacterial isolates showed a degree of resistance to the antibiotics tested. There was a high prevalence of multidrug resistant bacteria showing resistance to 3 - 8 drugs. The antagonistic effect of the bacterial isolates against selected fungi was determined. None of the isolates showed antagonistic potential against the fungal pathogens. However, the supposed antagonistic bacterial species can be genetically modified to produce secondary metabolites that will result in biocontrol.

Nutrient-Induced Growth of Coliform and HPC Bacteria in Drinking-Water Pipes

We conducted a study on a model drinking water distribution system to evaluate the impact of nutrient in the form of sodium acetate on the growth and survival of coliform and heterotrophic plate count (HPC) bacteria for a maximum of 21 days residence time of water in pipes. Our results show that, besides the nutrient added and the absence of any additional source of contamination and additional supply of nutrient, there was significant growth of the above mentioned bacteria in the pipes and bottles for a couple of days, after which the bacterial population began to decrease. The results indicate that the bacteria used the nutrient to grow and multiply until the nutrient was totally consumed and became depleted in the bulk water phase, after which the bacterial population reached a near stationary level and subsequently declined. This suggests the death of some of the bacteria and their dead cells were used by other bacteria for growth and survival. Using a detection limit of 3.3 CFU/100 mL for the coliforms, the study shows that after sometime, no bacteria were found in the water phase of the pipe, however, the biofilm in the pipes still harbored some of the bacteria. The results have revealed that the bacteria also have the tendency to move from the water phase to the biofilm since the latter provides a more suitable environment for bacteria to thrive on and grow, thus prolonging their survival in the system.

Growth retrieval of stressed bacterial cells: logic and contradictions

Study of bacterial stress response against an array of stress signals like heat shock and oxidative stress has been well accomplished so far.Several stress factors cause microorganisms to go under the viable but nonculturable state.However,the growth resuscitation of bacterial cells from such viable but nonculturable state is still obscure.Current review briefly focused on the growth revival of the viable but nonculturable cells and placed the possible model of growth resuscitation.The significance of such type of study on the viable but nonculturable cells principally relies upon clinical sectors whereby some pathogens are found to be latent for many days and thereby imparting the false negative results as well as in the food industries whereby the viable but nonculturable cells may cause massive damage in the public health upon their resuscitation.

The impact of heavy metals on bacterial tolerance of antibiotic resistance and growth in the aquatic environment of Vietnam

Heavy metals may induce bacterial antibiotic resistance and affect their growth in the ecosystem.In this study,we aim to determine bacterial growth and antibiotic resistance in the pressure of heavy metals.Observed the changing morphology by gram staining was checked for bacterial toleration with heavy metal,developing of the colony form unit(CFU)was analysed bacterial kinetic growths and their biofilm formation.The disk diffusion test was used to perform bacterial susceptibility profiles with Ceftazidime(30μg),Ceftriaxone(30μg),Colistin sulfate(10μg),Meropenem or Imipenem(10μg),Ciprofloxacin(5μg)and Azithromycin(15μg)and the CLSI was applied for interpreting the data.The bacterial morphology remarkably changed from normal to short,round shape at a high concentration of heavy metals after 1 month.Their changing shape adapted to heavy metals by survival growing and resisted to Azithromycin,Ciprofloxacin,and Colistin without biofilm formation after 1 month,that was continued increasing after 2 months.The bacterial growth and antibiotic resistance were significant differences between provinces(P=0.01),type of bacterial species,and concentration of heavy metals.These results indicate that heavy metals are a crucial factor-driven for enhancing bacterial adaptation in pollution water resources and inducing their antimicrobial resistance in the aquatic environment.

Anti-Bacterial and Flame Retardant for Cotton Fabric by One-Bath Finishing

A research on the process of cotton fabric flame-re-tarding,anti-bacterial finishing and one-bath finish-ing of anti-bacterial and flame-retarding is discussed.The flame retardant agent was phosphorous-contained,and the bacteriostatic finishing agent named SFR-1 wassynthesized.The flame retardancy of the fabric finishedcan meet the DOC FF3-71 Children Sleepwear Stan-dard.Its bacterial inhibiting capacity can meet and ex-ceed the requirements of similar products

Abnormal Secondary Growth and Histochemical Localization of Alkaloids in Root System of Aconitum flavum Hand.-Mazz.

[Objective] The purpose of this study was to clarify the structure,growth pattern and histochemical localization of alkaloids in root system of Aconitum flavum Hand.-Mazz.[Method] Paraffin sectioning and histochemistry were employed for performing the analysis in this study.[Result] The root system of Aconitum flavum Hand.-Mazz.consists of taproot,lateral root and adventitious root.The primary structure of root system is normal,but secondary structure shows abnormal.The cambium and the extra cambium of taproot form a ＂U＂-shaped secondary vascular bundle and tertiary bundle in abnormal secondary structure.The sieve tube group is made of little sieve tube group which is differentiated from primary phloem and cambium.Meanwhile,the secondary xylem in tuberous root also appears to be a ＂U＂ shape.Parenchyma cells of secondary phloem occupy most of the tuberous root.The sieve tube group of tuberous root is mainly differentiated from parenchyma cell of secondary phloem.[Conclusion] The difference in abnormal secondary structure of taproot and tuberous root are attributed to their varied cambium compose and activity pattern.Alkaloids are mainly accumulated in parenchyma cell of the inside cortex and between bundle in taproot,while parenchyma of secondary phloem and pith in tuberous root.

Effect of alginic acid decomposing bacterium on the growth of Laminaria japonica (Phaeophyceae)

We collected the diseased blades of Larninaria japonica from Yantai Sea Farm from October to December 2002, and the alginic acid decomposing bacterium on the diseased blade was isolated and purified, and was identified as A lteromonas espejiana. This bacterium was applied as the causative pathogen to infect the blades of L. japonica under laboratory conditions. The aim of the present study was to identify the effects of the bacterium on the growth of L. japonica, and to find the possibly effective mechanism. Results showed that： （1）The blades of L.japonica exhibited symptoms of lesion,bleaching and deteriortion when infected by the bacterium. and their growth and photosynthesis were dramatically suppressed. At the same time, the reactive oxygen species （ROS） generation enhanced obviously, and the relative membrane permeability increased significantly. The contents of malonaldehyde （MDA） and free fatty acid in the microsomol membrane greatly elevated, but the phospholipid content decreased. Result suggested an obvious peroxidation and deesterrification in the blades of L. japonica when infected by the bacterium. （2） The simultaneous assay on the antioxidant enzyme activities demonstrated that superoxide dismutase （SOD） and catalase （CAT） increased greatly when infected by the bacterium, but glutathione peroxidase （Gpx） and ascorbate peroxidase （APX） did not exhibit active responses to the bacterium throughout the experiment. （3） The histomorphological observations gave a distinctive evidence of the severity of the lesions as well as the relative abundance in the bacterial population on the blades after infection. The bacterium firstly invaded into the endodermis of L. japonica and gathered around there, and then resulted in the membrane damage, cells corruption and ultimately, the death of L. japonica.

Thermodynamic analysis of growth of ternary Ⅲ-Ⅴ semiconductor materials by molecular-beam epitaxy

Thermodynamic models for molecular-beam epitaxy（MBE） growth of ternary Ⅲ-Ⅴ semiconductor materials are proposed.These models are in agreement with our experimental materials InGaP/GaAs and InGaAs/InP,and reported GaAsP/GaAs and InAsP/InP in thermodynamic growth.The lattice strain energy △G and thermal decomposition sensitive to growth temperature are demonstrated in the models simultaneously.△G is the function of the alloy composition,which is affected by flux ratio and growth temperature directly.The calculation results reveal that flux ratio and growth temperature mainly influence the growth process.Thermodynamic model of quaternary InGaAsP/GaAs semiconductor material is discussed also.

Cyclooxygenase-2 and epithelial growth factor receptor up-regulation during progression of Barrett's esophagus to adenocarcinoma

AIM： To investigate the expression of cyclooxygenase-2 （COX-2） and epithelial growth factor receptor （EGFR） throughout the progression of Barrett＇s esophagus （BE）. METHODS： COX-2 and EGFR protein expressions were detected by using immunohistochemical method. A detailed cytomorphological changes were determined. Areas of COX-2 and EGFR expression were quantified by using computer Imaging System. RESULTS： The expressions of both COX-2 and EGFR increased along with the progression from BE to esophagus adenocarcinoma （EAC）. A positive correlation was found between COX-2 expression and EGFR expression. CONCLUSION： COX-2 and EGFR may be cooperative in the stepwise progression from BE to EAC, thereby leading to carcinogenesis.

Inhibitory effect of interferon-α-2b on expression of cyclooxygenase-2 and vascular endothelial growth factor in human hepatocellular carcinoma inoculated in nude mice

AIM： To evaluate the effects of interferon-α-2b （IFN- α-2b） on expression of cyclooxygenase-2 （COX-2） and vascular endothelial growth factor （VEGF） in human hepatocellular carcinoma （HCC） inoculated in nude mice and to study the underlying mechanism of IFN-α- 2b against HCC growth. METHODS： Thirb/-two nude mice bearing human HCC were randomly divided into four groups （n = 8）. On the 10th day after implantation of HCC cells, the mice in test groups （groups A, B and C） received IFN-α- 2b at a serial dose （10000 IU for group A, 20000 IU for group B, 40000 IU for group C sc daily） for 35 d. The mice in control group received normal saline （NS）. The growth conditions of transplanted tumors were observed. Both genes and proteins of COX-2 and VEGF were detected by RT-PCR and Western blot. Apoptosis of tumor cells in nude mice was detected by TUNEL assay after treatment with IFN-α-2b. RESULTS： Tumors were significantly smaller and had a lower weight in the IFN-α-2b treatment groups than those in the control group （P 〈 0.01）, and the tumor growth inhibition rate in groups A, B and C was 27.78%, 65.22% and 49.64%, respectively. The expression levels of both genes and proteins of COX-2 and VEGF were much lower in the IFN-α-2b treatment groups than in the control group （P 〈 0.01）. The apoptosis index （AI） of tumor cells in the IFN-α-2b treatment groups was markedly higher than that in the control group （P 〈 0.01）. Group B had a higher inhibition rate of tumor growth, a lower expression level of COX-2 and VEGF and a higher AI than groups A and C （P 〈 0.05）, but there was no significant difference between groups A and C. CONCLUSION： The inhibitory effects of IFN-α-2b on implanted tumor growth and apoptosis may be associated with the down-regulation of COX-2 and VEGF expression. There is a dose-effect relationship. The medium dose of IFN-α-2b for inhibiting tumor growth is 20 000 IU/d.

A continuous-discontinuous cellular automaton method for cracks growth and coalescence in brittle material

A method of continuous-discontinuous cellular automaton for modeling the growth and coalescence of multiple cracks in brittle material is presented. The method uses the level set to track arbitrary discontinuities, and calculation grids are independent of the discontinuities and no remeshing are required with the crack growing. Based on Grif- fith fracture theory and Mohr-Coulumb criterion, a mixed fracture criterion for multiple cracks growth in brittle mate- rial is proposed. The method treats the junction and coales- cence of multiple cracks, and junction criterion and coales- cence criterion for brittle material are given, too. Besides, in order to overcome the tracking error in the level set ap- proximation for crack junction and coalescence, a dichotomy searching algorithm is proposed. Introduced the above the- ories into continuous-discontinuous cellular automaton, the present method can be applied to solving multiple crack growth in brittle material, and only cell stiffness is needed and no assembled global stiffness is needed. Some numerical examples are given to shown that the present method is efficient and accurate for crack junction, coalescence and percolation problems.

3D atomic-scale growth characteristics of {10-12} twin in magnesium

In this work,we carried out three-dimensional(3D)atomic-scale study on the growth characteristics of{10-12}twin in magnesium(Mg).The study was performed by MD simulations on Mg single crystals with an initial twin nucleus structures.A detailed atomistic analysis reveals that a stabilized 3D{10-12}twin nucleus is bounded by basal/prismatic(BP)interfaces,prismatic/basal(PB)interfaces,and{10-11}interfaces.Later,a{10-12}twin boundary(TB)occurs at the junction of the BP and PB interface with the growth of the twin nucleus.In this process,two twinning mechanisms are involved:a pure-shuffle mechanism in which{10-11}interface migration along the[11-20]direction is mediated by atomic shuffle,and a glide-shuffle mechanism in which BP/PB and{10-12}TB movements are realized by the migration of disconnections along the relevant interfaces.In addition,we systematically investigate the stress state associated with the activation of twinning,aiming to discover the intrinsic relationship of the elastic stress field to twin growth on an atomic scale.The results suggest that the elastic stress in the matrix is an important driving force for twin growth,much similar to what stress does for a crack.In addition,it is rather remarkable that the{10-11}interface has a greater ability to migrate than other interfaces,and this is thought to be a main factor for the rapid growth of a{10-12}twin.