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121.
Summary. Holospora obtusa is a Gram-negative bacterium inhabiting the macronucleus of the ciliate Paramecium caudatum. Experimental infection with H. obtusa was carried out under nocodazole treatment. Nocodazole has been shown to cause disassembly of the cytoplasmic microtubules
radiating from the cytopharynx and postoral fibers in P. caudatum. Treatment with this drug did not prevent the ingestion of both prey bacteria and H. obtusa, but it reduced the phagosome number and affected cyclosis. In situ hybridization revealed infectious forms of this endobiont
very close to the macronucleus, but never inside it. These results indicate that disassembly of microtubules does not impair
transportation of the infectious forms of H. obtusa in the cytoplasm, but that it completely blocks the invasion of the nucleus by the bacteria.
Correspondence and reprints: Department of Cytology and Histology, Faculty of Biology and Soil Sciences, Saint Petersburg
State University, Universitetskaya naberezhnaya 7/9, 199034 Saint Petersburg, Russia. 相似文献
122.
Kabaivanova L Dobreva E Dimitrov P Emanuilova E 《Journal of industrial microbiology & biotechnology》2005,32(1):7-11
Cells of the moderately thermophilic Bacillus sp. UG-5B strain, producing nitrilase (EC3.5.5.1), which converts nitriles directly to the corresponding acid and ammonia, were immobilized using different types of matrices and techniques. A variety of sol-gel silica hybrids were tested for entrapment and adsorption of bacterial cells as well as chemical binding on polysulphone membranes. Activation of the matrix surface with formaldehyde led to an increase in immobilization efficiency and operational stability of the biocatalysts. Among the supports screened, membranes gave the best results for enzyme activity and especially operational stability, with retention of 100% activity after eight reaction cycles. 相似文献
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124.
一个新的高温产氢菌及产氢特性的研究 总被引:11,自引:0,他引:11
利用Hungate滚管技术从西藏山南地区热泉淤泥中分离到一株高温产氢的厌氧发酵细菌T42。菌株T42革兰氏染色反应为阴性,但KOH裂解试验证实其为革兰氏阳性杆菌。菌体大小为0.7μm~0.9μm×3.2μm~7μm,不运动,不产芽孢。其生长温度范围为32℃~69℃,最适生长温度为60℃~62℃,生长pH范围为5.0~8.8,最适生长pH为7.0~7.5,代时30min。有机氮源是T42菌株的必需生长因子。菌株T42利用淀粉、纤维二糖、蔗糖、麦芽糖、糊精、果糖、糖原和海藻糖等底物生长并发酵产氢,发酵葡萄糖的终产物为乙酸、乙醇、H2和CO2。G C含量为31.2mol%。系统发育分析表明菌株T42与Thermobrachium celere和Caloramator indicus位于同一分支,生理生化特征也表明菌株T42应是Thermobrachium属的一个新菌株,在中国普通微生物菌种保藏中心的保藏号为AS1.5039。菌株T42的最佳产氢初始pH为7.2,最佳产氢温度为62℃,其氢转化率为1.06mol H2/mol葡萄糖,最大产氢速率为24.0mmol H2/gDW/h。20mmol/L的Mg2 和2mmol/L的Fe2 可分别提高菌株T42的产氢量20%和23.3%,而Ni2 对其产氢无明显的作用。当菌株T42和热自养甲烷热杆菌(Methanothermobacter thermautotrophicus)Z245共培养时,由于降低了氢分压,使其葡萄糖利用率和氢产量分别提高1倍和2.8倍,发酵产物乙酸和乙醇的比例也从1提高到1.7。 相似文献
125.
126.
Yang LF Jiang JQ Zhao BS Zhang B Feng de Q Lu WD Wang L Yang SS 《FEMS microbiology letters》2006,255(1):89-95
A gene encoding a Na(+)/H(+) antiporter was cloned from a chromosomal DNA of Halobacillus dabanensis strain D-8(T) by functional complementation. Its presence enabled the antiporter-deficient Escherichia coli strain KNabc to survive in the presence of 0.2 M NaCl or 5 mM LiCl. The gene was sequenced and designated as nhaH. The deduced amino-acid sequence of NhaH consists of 403 residues with a calculated molecular mass of 43,481 Da, which was 54% identical and 76% similar to the NhaG Na(+)/H(+) antiporter of Bacillus subtilis. The hydropathy profile was characteristic of a membrane protein with 12 putative transmembrane domains. Everted membrane vesicles prepared from E. coli cells carrying nhaH exhibited Na(+)/H(+) as well as Li(+)/H(+) antiporter activity, which was pH-dependent with highest activities at pH 8.5-9.0 and at pH 8.5, respectively. Moreover, nhaH confers upon E. coli KNabc cells the ability to grow under alkaline conditions. 相似文献
127.
128.
Antioxidative properties of Lactobacillus sake upon exposure to elevated oxygen concentrations 总被引:15,自引:0,他引:15
The ability of bacteria to overcome oxidative stress is related to the levels and types of antioxidative mechanisms which they possess. In this study, the antioxidative properties in Lactobacillus sake strains from different food origins were determined at low temperature (8 degrees C) and upon exposure to oxygen levels between 20 and 90% O(2). The L. sake strains tested grew well at 8 degrees C and in the presence of 20% O(2), however, most of the strains could not grow at O(2) levels as high as 50 and/or 90%. Cell-free extracts of all strains possessed certain levels of hydroxyl radical scavenging, metal chelating and reducing capacities essential for growth of cells at ambient O(2). At elevated O(2) concentrations, a high H(2)O(2) splitting capacity and low specific rates of H(2)O(2) production were demonstrated in the O(2)-insensitive strain L. sake NCFB 2813, which could grow at elevated O(2) conditions. Although H(2)O(2) was generated in the O(2)-sensitive L. sake DSM 6333 at levels which were not directly toxic to the cells (<0.2 mM), we can conclude that its removal is essential for cell protection at elevated O(2) conditions. 相似文献
129.
130.
Arne Holst-Jensen Yves Bertheau Marc de Loose Lutz Grohmann Sandrine Hamels Lotte Hougs Dany Morisset Sven Pecoraro Maria Pla Marc Van den Bulcke Doerte Wulff 《Biotechnology advances》2012
Genetically modified plants, in the following referred to as genetically modified organisms or GMOs, have been commercially grown for almost two decades. In 2010 approximately 10% of the total global crop acreage was planted with GMOs (James, 2011). More than 30 countries have been growing commercial GMOs, and many more have performed field trials. Although the majority of commercial GMOs both in terms of acreage and specific events belong to the four species: soybean, maize, cotton and rapeseed, there are another 20 + species where GMOs are commercialized or in the pipeline for commercialization. The number of GMOs cultivated in field trials or for commercial production has constantly increased during this time period. So have the number of species, the number of countries involved, the diversity of novel (added) genetic elements and the global trade. All of these factors contribute to the increasing complexity of detecting and correctly identifying GMO derived material. Many jurisdictions, including the European Union (EU), legally distinguish between authorized (and therefore legal) and un-authorized (and therefore illegal) GMOs. Information about the developments, field trials, authorizations, cultivation, trade and observations made in the official GMO control laboratories in different countries around the world is often limited, despite several attempts such as the OECD BioTrack for voluntary dissemination of data. This lack of information inevitably makes it challenging to detect and identify GMOs, especially the un-authorized GMOs. The present paper reviews the state of the art technologies and approaches in light of coverage, practicability, sensitivity and limitations. Emphasis is put on exemplifying practical detection of un-authorized GMOs. Although this paper has a European (EU) bias when examples are given, the contents have global relevance. 相似文献