四川宜宾七种中药提取物体外抗菌活性研究

用肉汤二倍稀释法和琼脂平板培养计数法,研究四川宜宾七种中药的提取物对大肠杆菌、沙门氏菌和巴氏杆菌的体外抑制作用.结果表明：黄柏提取物的抗菌活性最强,最小抑菌浓度(Minimum inhibitory concentration,MIC)为15．6~125 mg·mL-1,最小杀菌浓度(Minimum bactericidal concentration,MBC)为31．25~250 mg·mL-1;栀子提取物抗菌活性次之,MIC 为62．5~125 mg·mL-1,MBC 为125~＞250 mg·mL-1;佛手提取物有较稳定的抗菌活性,MIC均为125 mg·mL-1,MBC为125 mg·mL-1和250 mg·mL-1;姜黄、杜仲、何首乌、细毡毛忍冬的提取物抗菌活性相对较差,大部分 MIC≥250 mg·mL-1.说明四川宜宾的黄柏和栀子的提取物抗菌活性较强,佛手提取物抗菌活性较稳定,有进一步研究的价值.     

Pyranopyrazoles as efficient antimicrobial agents: Green,one pot and multicomponent approach

Innovative therapeutic heterocycles having precisely thiadiazolyl-pyranopyrazole fragments were prepared by using the ecofriendly synthetic route. Entire compounds formed in quantitative yields. All the composites tested for their antimicrobial effectiveness against four microbial, two beneficial fungi’s and accurately measured the minimum inhibitory concentrations (MIC and MBC/MFC), along with some initial structure activity relationships (SARs) also discussed. From the biological outcomes, the motif 6f provided an outstanding activity against all six pathogens. The possible presence of a nitro substituent on this composite may undoubtedly enhance the activity. In addition, amalgams 6d, 6g and 6l displayed promising antimicrobial results. This may be justified to the presence of electron capture group attached to the benzene ring, while the combinations 6j and 6k were zero effect towards all bacterial strains. The other compounds were excellent to low antimicrobial efficiency. The intriguing point was observed that all the active compounds had in common immense antibacterial effectiveness on Gram-negative bacteria than Gram-positive one and more antifungal activity on A. niger compare to other fungus. All things considered and suggested that this outstanding green synthetic approach is used to develop biological active compounds. On top of that, biological results confirmed that these biologically energetic motifs suitable for additional preclinical examine with the aim of standing novel innovative drugs.     

Synthesis of benzoylthiourea derivatives and analysis of their antibacterial performance against planktonic Staphylococcus aureus and its biofilms

Following the appearance of several antimicrobial agents to control the spread of infections, two major challenges have emerged: (i) the occurrence and blowout of multiresistant bacteria and the increase of chronic diseases and (ii) difficult-to-eradicate infections. In this study, we tested five benzoylthiourea derivatives for their ability to inhibit and stop bacterial growth and evaluated the possible influence of 1,2,4-triazolyl-benzoylthiourea derivative 4 on the formation and eradication of Staphylococcus aureus biofilms. Benzoylthiourea derivatives 4 , 6 , 10 , 11 and 13 were obtained in one or two steps with low cost and subjected to tests to identify their minimum inhibitory concentration (MIC) and minimum bactericidal concentration. In vitro tests were also performed to assess their effects on biofilm formation and in preformed biofilms and scanning electron microscopy was used to visualize the effects on biofilm formation. The 1,2,4-triazolyl-benzoylthiourea derivative 4 showed bacteriostatic activity against the S. aureus HU25 clinical strain with an MIC of 16 µg ml⁻¹, which is below the toxic concentration (at 2500 µg ml⁻¹, 62·25% of the cells remained viable). Compound 4 also effectively prevented biofilm formation at the three subinhibitory concentrations tested (1/2 MIC, 1/4 MIC and 1/8 MIC) as confirmed by scanning electron microscopy. For breakdown of formed biofilms, the main influence was at a subinhibitory concentration (1/2 MIC). These findings make compound 4 a strong candidate for studies on the development of new antimicrobial and antibiofilm agents.     

Enhanced litter input rather than changes in litter chemistry drive soil carbon and nitrogen cycles under elevated CO2: a microcosm study

Elevated CO₂ has been shown to stimulate plant productivity and change litter chemistry. These changes in substrate availability may then alter soil microbial processes and possibly lead to feedback effects on N availability. However, the strength of this feedback, and even its direction, remains unknown. Further, uncertainty remains whether sustained increases in net primary productivity will lead to increased long‐term C storage in soil. To examine how changes in litter chemistry and productivity under elevated CO₂ influence microbial activity and soil C formation, we conducted a 230‐day microcosm incubation with five levels of litter addition rate that represented 0, 0.5, 1.0, 1.4 and 1.8 × litterfall rates observed in the field for aspen stand growing under control treatments at the Aspen FACE experiment in Rhinelander, WI, USA. Litter and soil samples were collected from the corresponding field control and elevated CO₂ treatment after trees were exposed to elevated CO₂ (560 ppm) for 7 years. We found that small decreases in litter [N] under elevated CO₂ had minor effects on microbial biomass carbon, microbial biomass nitrogen and dissolved inorganic nitrogen. Increasing litter addition rates resulted in linear increase in total C and new C (C from added litter) that accumulated in whole soil as well as in the high density soil fraction (HDF), despite higher cumulative C loss by respiration. Total N retained in whole soil and in HDF also increased with litter addition rate as did accumulation of new C per unit of accumulated N. Based on our microcosm comparisons and regression models, we expected that enhanced C inputs rather than changes in litter chemistry would be the dominant factor controlling soil C levels and turnover at the current level of litter production rate (230 g C m⁻² yr⁻¹ under ambient CO₂). However, our analysis also suggests that the effects of changes in biochemistry caused by elevated CO₂ could become significant at a higher level of litter production rate, with a trend of decreasing total C in HDF, new C in whole soil, as well as total N in whole soil and HDF.     

Effects of water gradients on soil enzyme activity and active organic carbon composition under Carex lasiocarpa marsh

The responses of soil enzyme activity of freshwater marsh, microbial biomass carbon (MBC), dissolved organic carbon (DOC) and aboveground biomass to water gradients were studied with Carex lasiocarpa pot culture experiment. The relationships between soil enzyme activity and MBC, DOC and aboveground biomass were discussed. The water gradients were W1, 15 cm; W2, ?5 cm; W3, ?5–5 cm; W4, submerged. The results indicated that acid phosphatase, invertase and urease activities were decreased with the increase of water level, while catalase activity was increased with moisture content increasing. Drying-wetting alternation (W3) increased soil enzyme activities if compared with W1. MBC content followed the order of W3 > W1 > W2 > W4, and the activities of invertase, urease and catalase were significantly positively correlated with MBC (p < 0.05). DOC content presented the order of W4 > W1 > W3 > W2, and the activities of urease and acid phosphatase were most significantly negatively correlated with DOC (p < 0.01). In addition, drying-wetting alternation promoted the growth of Carex lasiocarpa. When water submerged plants, the growth of Carex lasiocarpa was significantly inhibited. The aboveground biomass was positively related to soil enzyme activities. There were close relationships between the activities of invertase, urease and catalase and the growth situation of Carex lasiocarpa.     

Two interdependent mechanisms of antimicrobial activity allow for efficient killing in nylon-3-based polymeric mimics of innate immunity peptides

Novel synthetic mimics of antimicrobial peptides have been developed to exhibit structural properties and antimicrobial activity similar to those of natural antimicrobial peptides (AMPs) of the innate immune system. These molecules have a number of potential advantages over conventional antibiotics, including reduced bacterial resistance, cost-effective preparation, and customizable designs. In this study, we investigate a family of nylon-3 polymer-based antimicrobials. By combining vesicle dye leakage, bacterial permeation, and bactericidal assays with small-angle X-ray scattering (SAXS), we find that these polymers are capable of two interdependent mechanisms of action: permeation of bacterial membranes and binding to intracellular targets such as DNA, with the latter necessarily dependent on the former. We systemically examine polymer-induced membrane deformation modes across a range of lipid compositions that mimic both bacteria and mammalian cell membranes. The results show that the polymers' ability to generate negative Gaussian curvature (NGC), a topological requirement for membrane permeation and cellular entry, in model Escherichia coli membranes correlates with their ability to permeate membranes without complete membrane disruption and kill E. coli cells. Our findings suggest that these polymers operate with a concentration-dependent mechanism of action: at low concentrations permeation and DNA binding occur without membrane disruption, while at high concentrations complete disruption of the membrane occurs. This article is part of a Special Issue entitled: Interfacially Active Peptides and Proteins. Guest Editors: William C. Wimley and Kalina Hristova.     

5种抗生素对4株化脓隐秘杆菌的最小杀菌浓度测定

目的测定诺氟沙星、恩诺沙星、环丙沙星、安普霉素和庆大霉素5种抗生素对林麝化脓隐秘杆菌的最小杀菌浓度,为选择治疗林麝脓肿病的有效药物提供指导。方法将菌液与不同浓度的抗生素混合作用30min,再加入中和剂作用10min,吸取300mL作用液均匀涂布在胎牛血清培养基上,38℃培养48h,观察并记录。结果 5种抗生素对化脓隐秘杆菌的最小杀菌浓度不一致,对4株菌杀菌效果相对较好的药物为环丙沙星(CIP),但对TP1需要较高浓度(128μg/mL)。结论喹诺酮类抗生素虽然抑菌效果较明显,但要完全杀死化脓隐秘杆菌却需要较高浓度,这很可能与化脓隐秘杆菌菌膜的存在有关。到目前为止,治疗林麝脓肿病的首选药物为喹诺酮类抗生素,尤以环丙沙星效果最佳。     

中亚热带常绿阔叶林不同演替阶段土壤活性有机碳含量及季节动态

为探明不同演替阶段土壤碳吸存潜力,选取演替时间为15a(演替初期)、47a(演替中期)、110a(演替后期)3个中亚热带常绿阔叶林,分析了各演替阶段的土壤有机碳(SOC)含量以及土壤微生物量碳(MBC)、可溶性碳(DOC)和微生物熵(SMQ)的季节变化。结果表明:演替中、后期不同土层的土壤SOC、MBC、DOC含量和SMQ均显著高于演替初期(P<0.05);与演替中期相比,演替后期土壤MBC、DOC含量有所降低,SOC含量和SMQ无显著差异。土壤SOC、MBC和DOC含量随土层加深而显著性降低(演替初、中期DOC除外),并随演替进行逐渐向腐殖质层富集。不同演替阶段MBC、DOC和SMQ均有显著季节变化,最低值出现在秋季,最高值随演替进程由冬季逐步转向夏季。相关分析表明,不同演替阶段土壤活性有机碳含量与土壤有机碳含量极显著相关(P<0.01),且土壤活性有机碳(MBC、DOC)和SMQ对土壤碳库变化更为敏感。     

Mutagenicity testing of benomyl, methyl-2-benzimidazole carbamate, streptozotocin and N-methyl-N'-nitro-N-nitrosoguanidine in Salmonella typhimurium in vitro and in rodent host-mediated assays.

The fungicide benomyl and its commercial preparations Fundazol 50WP and Benlate 50WP and the benomyl metabolite methyl-2-benzimidazole carbamate and its commercial preparation MBC 50WP were tested for mutagenicity in in vitro spot tests, in microsomal plate assay, in liquid-culture treatments, or in rodent host-mediated assay. The base-pair substitution Salmonella typhimurium mutant hisG46 and the hisG46-bearing uvrB excision-repair-deficient mutants TA100, TA1530, TA1535 or TA1950 were used as test organisms. Complete genotypic information of these mutants is given in Ames et al. [2]. Captain 50WP, streptozotocin (SZN), N-methyl-N'-nitro-N-nitrosoguanidine (MNNG), 2-aminopurine and N-acetylaminofluorene were used as positive control compounds. In nonoverlay spot tests Benlate 50WP was not mutagenic over a dose range of 50-5000 microgram/spot in hisG46 and TA1535. In overlay spot tests 50 or 100 microgram/spot Benomyl, MBC, Fundazol 50WP, Benlate 50WP and MBC 50WP were tested in hisG46, TA1530 or TA1950. Only a non-commercial MBC sample at 100 microgram/spot showed weak mutagenic activity in hisG46. In microsomal activation plate assay MBC, benomyl, Fundazol 50WP and Benlate 50WP were tested in TA100 over a dose range of 50-2000 microgram/plate. None of the compounds showed mutagenicity. In a 20-h liquid-culture treatment 10, 100, 1000 and 10 000 microgram/ml Fundazol 50WP were not mutagenic in TA 30. In 1-h liquid-culture treatments benomyl, Benlate 50WP or Fundazol 50WP failed to induce mutations in hisG46, TA100 or TA1950 over a dose range of 0.25-1000 microgram/ml. Appropriate positive controls were mutagenic in each experiment. The consistently negative results in this study with commercial MBC and benomyl preparations are contrary to positive results reported earlier with similar methods and similar commercial preparations. Possible reasons to explain the different results are presented. The alkylating agents SZN and MNNG induced fewer mutations in TA1530 and TA1950 uvrB excision-repair-deficient strains than in the hisG46 excision-proficient strain, indicating that with these mutagens excision-repair is also a mutation-prone process. In rodent host-mediated assays with Fundazol 50WP in mice 3 consecutive subcutaneous hourly doses of 500 mg/kg in hisG46 and TA1950 and in rats or mice an oral dose of 4000 mg/kg in TA1950 were not mutagenic. The positive control SZN was mutagenic.