微量液体培养基最低抑菌浓度法与罗氏比例法在结核分枝杆菌药敏试验中的价值比较

目的比较微量液体培养基最低抑菌浓度(MIC)法与罗氏比例法在结核分枝杆菌药敏试验中的临床价值。方法以100株结核分枝杆菌菌株(由辽宁省结核实验室提供)为研究样本,分别采用罗氏比例法与微量液体培养基MIC法检测结核分枝杆菌的药物敏感性。结果微量液体培养基MIC法与罗氏比例法检测结核分枝杆菌对乙胺丁醇、二卡那霉素、利福平、异烟肼、氧氟沙星、卷曲霉素药物的敏感性比较,差异无统计学意义(P> 0.05)。结论微量液体培养基MIC法应用于结核分枝杆菌药敏试验中与罗氏比例法有着良好的一致性,且检测速度快,经济适用性好,能够为临床指导结核病用药提供帮助。

湖泊沉积物中微量金属二次迁移过程中微生物作用的实验研究

蓄积在湖泊沉积物中污染物质某些情况下可以成为威胁上覆水体水质安全的二次污染源．根据贵州省阿哈湖季节性缺氧的特性,通过控制氧化还原状况,设计了对该湖沉积物-水柱的原样／抑菌条件的培养实验．实验发现,微生物活动对界面附近氧化还原反应具有控制作用;改变水体的含氧状况可以显著影响上覆水体水质,包括表观性状和水体中污染物含量．聚类分析结果表明,早期成岩过程中Mn,Ga,SO4 2-,Cu,Cr,Pb和Co,Ni,Fe,Sc,V,Rb两大类分别具有相似的地球化学行为．根据实验结果,计算了厌氧培养过程中,微量元素的最大释放量,发现铁、锰在厌氧过程中可以大量向水体释放．

Chemical Compositions and Antibacterial Activity of Essential Oil from Thymus Seedlings of Tissue Culture

[Objective] This study aimed to compare and analyze the chemical compositions, the relative contents and the antibacterial activity of the essential oils extracted from the tissue culture seedlings, the aseptic seedlings and the common seedlings from seeds of Thymus vulgaris. [Method] The essential oil was extracted by steam distillation; the chemical compositions and their relative contents were analyzed by gas chromatography-mass spectrometry （GC/MS） and peak area normalization method; and the antimicrobial activity was tested by filter paper method. [Result] A total of 54 compositions were identified from these three samples, they had similar main compositions： thymol, m-Cymene, terpinene and so on, and these compositions were slightly different in contents. In addition, the essential oils from these three samples exhibited obvious antibacterial effect against Escherichia coli and Staphylococcus aureus, in which the antibacterial activity against S. aureus was stronger than against E. coli. [Conclusion] It is possible to produce essential oil by tissue culture technology; the main compositions and antibacterial activity of the oils remained almost the same.

Inhibition of norsolorinic acid accumulation to Aspergillus parasiticus by marine actinomycetes

Thirty-six strains of marine actinomycetes were isolated from a sample of marine sediment collected from the Yellow Sea and evaluated in terms of their inhibitory activity on the growth of Aspergillus parasiticus and the production of norsolorinic acid using dual culture plate assay and agar diffusion methods.Among them,three strains showed strong antifungal activity and were subsequently identified as Streptomyces sp.by 16 S rRNA gene sequencing analysis.The supernatant from the fermentation of the MA01 strain was extracted sequentially with chloroform and ethyl acetate,and the activities of the extracts were determined by tip culture assay.The assay results show that both extracts inhibited mycelium growth and toxin production,and the inhibitory activities of the extracts increased as their concentrations increased.The results of this study suggest that marine actinomycetes are biologically important for the control of mycotoxins,and that these bacteria could be used as novel biopesticides against mycotoxins.

Isolation and structural identification of two bioactive phenazines from Streptomyces griseoluteus P510

Phenazine antibiotics phenazine-l-carboxylic acid （PCA） and l-hydroxyphenazine （1-OH-PHZ） were purified from culture broth and mycelia ofStreptomyces griseoluteus P510, Both PCA and 1 -OH-PHZ exhibit strong antifun- gal activity against six plant pathogens, especially Fusarium oxysporium, with minimal inhibition concentrations less than I and 2/ag, ml- 1 for PCA and 1-OH-PHZ, respectively, The presence of PCA and 1 -OH-PHZ indicates that S. griseoluteus PSlO can be used as a potential source of pesticides,

The Use of Str Mutations for Enhancement of Hydrogen Peroxide Formation by Lactobacillus Delbrueckii MH-IO at Refrigeration

The strains ofLactobacillus delbrueckii subsp, lactis widely used in food preservation due to ability produce high amount of hydrogen peroxide at refrigerator temperatures to inhibit food-borne pathogens and psychrophilic spoilage microorganisms. In order to improve of bio-preservation efficacy ofL. delbrueckii MH 10 mutations causing resistance to streptomycin （str） were used. Among UV-mutagenized population of L. delbruecla＇i three str mutants producing high amounts of H2O2 were selected. Sir mutants produced significant amounts of hydrogen peroxide 50-60 μg/ml in sodium phosphate buffer （0.2 M, pH 6.5） and in beef broth （BB） at 5 ℃ for 5 days submerged cultivation without of growth. Evaluation mutants antibacterialactivity at refrigeration temperatures against food-borne pathogen Escherichia coli O157：H7 revealed elimination of pathogen total number up to practically undetectable amount for 3 days. In case of solid-state cultivation on agar-based medium, disks soaked by mutant cells suspensions formed larger inhibitory zones on E. coli O157：H7 lawn for one-day cold exposition. The size of inhibition zone depends on concentration of LAB cells. Str mutants L. delbrueckii reduced initial amount 2 - 105 of E. coil O 157：H7 in ground beef up to 3 log for 3 days of solid-state cocultivation when the wild strain reduced only 2 log. The application ofL. delbrueckii mutants did not cause any changes in sensory characteristics of ground beef, moreover promotes expanding of shelf-life due to inhibition of psychrophilic spoilage microorganisms.

Diversity and Antimicrobial Activity of Cultivable Halophilic Archaea from Three Algerian Sites

Hypersaline environments are colonized by communities of microorganisms, which developed adaptations from halotolerant to extreme halophilic lifestyles. Twenty-four halophilic archaeal strains were isolated from three Algerian hypersaline sites, including the solar salterns in Ichekaben and two natural salt lakes at Ouargla and Oran. Almost full-length 16S rRNA genes were amplified using archaeal-specific primers, sequenced and phylogenetically analyzed. Three isolates from the salt lake of Ouargla were affiliated to Halorubrum sp., while six isolates from Ichekaben were Natrinema sp.. The remaining strains belonged to the genus Haloarcula, which was identified in the three Algerian sites. A phylogenetic tree of Haloarcula sp. including the two copies of the 16S rRNA gene, showed that two strains group with Haloarcula hispanica, while the other 13 cluster with OHF-1/OHF-2 isolated from French commercial salt. Both Natrinema sp. and Haloarcula sp. were persistent at Ichekaben. For the six Natrinema sp. isolates, this observation correlates with their capacity to produce antimicrobial compounds, and a DNA fragment closely related to the halocin C8 gene was amplified for five strains.