尼泊尔马桑根瘤内生菌纯培养物的质粒检测

采用胶内裂解法快速检测了21株马桑根瘤内生菌纯培养物和4株弗兰克氏菌参考菌株的质粒,其中有5株马桑分离菌株和1株参考菌株含有质粒。除马桑菌株和参考菌株各有1株携带2个质粒外,其它菌株均只含有1个质粒。这些质粒的分子量约为13～20kb。根据所含质粒的大小和数目,将21株马桑分离菌株划分成4个质粒类群。实验还对菌丝体生长,细胞酶解和裂解等条件对质粒检测效果的影响进行了探讨。     

EFFECTIVE METHOD FOR DRY INOCULATION of BACTERIAL CULTURES

An effective way for inoculation of bacteria into dry foods/ingredients that gives a uniform mixture was developed. In the first part of this experiment, Salmonella typhimurium was successfully inoculated into chalk. Chalk tubes were weighed then soaked in a broth with S. typhimurium and allowed to dry back to their original weight. the dried chalk was made into a powder form. A viable cell count of this chalk, using a selective media for S. typhimurium , showed that the organism survived the drying while entrapped in the chalk. the "charged" chalk was used in an experiment as a dry inoculum where it was mixed with a low-moisture poultry feed. In comparison to a liquid inoculum, the "charged" chalk was a superior way of inoculating into dry particles because it created a more homogenous mixture with the feed without altering any properties of the feed itself. the second part of this experiment entailed a shelf-life study of the "charged" chalk. the same procedures for inoculating chalk were done using ten different cultures including Bacillus cereus, Clostridium perfringens, Escherichia coli, Enterobacter aerogenes, Lactobacillus plantarum, Listeria monocytogenes, Pseudomonas aeruginosa, Salmonella typhimurium, Staphylococcus aureus , and Streptococcus faecalis. Data showed that the cultures are stable in the chalk for at least six months.     

A SIMPLIFIED METHOD FOR THE PREPARATION OF EGG YOLK MEDIA

SUMMARY: Difficulties with filtration in the preparation of egg yolk media were overcome by preparing the yolk emulsion with distilled water instead of saline. The turbidity of the final medium was related to its sodium chloride content.     

A NEW CHEMICAL METHOD FOR QUANTIFYING MELANIN1

—A direct chemical method for the estimation of absolute amounts of synthetic melanin is established by the use of sodium borohydride, a mild reducing agent for the ketonic or aldehyde carbonyl group. Sodium borohydride not only solubilized the melanins obtained from various precursors, but it also restored aromatic characteristics in the absorption spectra. The solubilized melanin has also been used with a radio-assay method for quantification of synthetic melanin. With this method of solubilization, the presence of lipids or proteins does not alter the linearity of the assay. The limiting amount of melanin detected by this method is 4-5 μg/ml of the final solution.     

A NEW FACILE METHOD FOR SPIN-LABELING OF OLIGONUCLEOTIDES

A new facile method for spin-labeling suitable for DNA and RNA oligonucleotides is presented. The nitroxide 3-ethenyl-2,2,5,5-tetramethyl-pyrrolin-1-yloxy was directly introduced during automated solid-phase synthesis by a Pd(0) cross coupling reaction. The main advantages of this procedure are the small amount of spin-label needed for the derivatisation of the oligonucleotide and the high coupling efficiency on the solid phase.     

培养原始生殖细胞的新方法

为探讨原始生殖细胞(primordial germ cells,PGCs)在体外长期增殖、生长并长期保持分化潜能的新方法,我们将PGCs分别与睾丸支持细胞(Sertoli cells,SCs)和同源生殖嵴成纤维细胞共培养。结果与SCs共培养的PGCs集落明显多于同源生殖嵴成纤维细胞共培养PGCs集落,传代次数也显著多于同源生殖嵴成纤维细胞．目前与SCs共培养的PGCs已成功传代培养至了第51代。因此我们认为PGCs与SCs共培养,可有效提高原始生殖细胞在体外的增殖能力并可长期维持干细胞的特性。     

一种弗兰克氏菌分种新方法的探讨

弗兰克氏菌是非豆科植物共生固氮菌,目前已发现200多种。因其生长缓慢,许多传统的分类方法对它不合适,所以弗兰克氏菌的分类工作仍处于十分混乱的阶段。目前世界上公认弗兰克氏菌是放线菌的一个属,但没有确定的种名,寻找合适的分种方法十分迫切。我们选择16S-23S rRNA基因间隔区的序列作为划分弗兰克氏菌种的研究对象,现将结果简报如下。 1 材料和方法 1.1 菌种 101、114、8201,2129菌株分离自云南省西双版纳地区,101和114菌株是从木麻黄根瘤中分离到的,8201和2129菌株分别来自赤杨和杨梅根瘤。ArI_4和PtI_1菌株分别来自美国赤杨和潘尔稀根瘤。 1.2 DNA的提取