Detection of polyhydroxyalkanoate-accumulating bacteria from domestic wastewater treatment plant using highly sensitive PCR primers

Polyhydroxyalkanoate (PHA) is a class of biodegradable plastics that have great potential applications in the near future. In this study, the micro-biodiversity and productivity of PHA-accumulating bacteria in activated sludge from a domestic wastewater treatment plant were investigated. A previously reported primer set and a selfdesigned primer set (phaCF1BO/phaCR2BO) were both used to amplify the PHA synthase (phaC) gene of isolated colonies. The new primers demonstrated higher sensitivity for phaC, and combining the PCR results of the two primer sets was able to widen the range of detected genera and raise the sensitivity to nearly 90%. Results showed that 85.3% of the identified bacteria were Gram-negative, with Ralstonia as the dominant genus, and 14.7% were Gram-positive. In addition, Zoogloea and Rhizobium contained the highest amounts of intracellular PHA. It is apparent that glucose was a better carbon source than pentone or tryptone for promoting PHA production in Micrococcus. Two different classes, class I and class II, of phaC were detected from alphaproteobacteria, betaproteobacteria, and gammaproteobacteria, indicating the wide diversity of PHA-accumulating bacteria in this particular sampling site. Simultaneous wastewater treatment and PHA production is promising by adopting the high PHAaccumulating bacteria isolated from activated sludge.     

Three critical hydrogen bonds determine the catalytic activity of the Diels-Alderase ribozyme

Compared to protein enzymes, our knowledge about how RNA accelerates chemical reactions is rather limited. The crystal structures of a ribozyme that catalyzes Diels–Alder reactions suggest a rich tertiary architecture responsible for catalysis. In this study, we systematically probe the relevance of crystallographically observed ground-state interactions for catalytic function using atomic mutagenesis in combination with various analytical techniques. The largest energetic contribution apparently arises from the precise shape complementarity between transition state and catalytic pocket: A single point mutant that folds correctly into the tertiary structure but lacks one H-bond that normally stabilizes the pocket is completely inactive. In the rate-limiting chemical step, the dienophile is furthermore activated by two weak H-bonds that contribute ∼7–8 kJ/mol to transition state stabilization, as indicated by the 25-fold slower reaction rates of deletion mutants. These H-bonds are also responsible for the tight binding of the Diels–Alder product by the ribozyme that causes product inhibition. For high catalytic activity, the ribozyme requires a fine-tuned balance between rigidity and flexibility that is determined by the combined action of one inter-strand H-bond and one magnesium ion. A sharp 360° turn reminiscent of the T-loop motif observed in tRNA is found to be important for catalytic function.     

华北平原罗布麻种群生殖分株数量特征及变化规律

通过大样本取样调查,研究了华北平原罗布麻种群生殖分株的数量特征和生殖分配规律．结果表明,在籽粒完熟期,罗布麻种群单个生殖分株重为10．38±7．78g,蒴果生物量和蒴果数分别为1．57±1．59g和7．60±6．56个;种子生物量和种子数分别为0．34±0．33g和582．3±558．7个;生殖分配Ⅰ和生殖分配Ⅱ分别为12．98±7．94和2．75±1．69％．蒴果和种子形成分别需要分株积累1．42和1．77g以上的生物量．蒴果生物量、葫果数、种子生物量、种子数分别与分株总生物量呈极显著的（P〈0．01）线性正相关关系;蒴果数、种子数与茎叶生物量分配呈极显著的（P〈0．01）线性负相关关系;生殖分配Ⅰ、生殖分配Ⅱ和叶生物量分配呈极显著的（P〈0．01）线性负相关关系．单葫果的重量、种子重、种子数、种子毛重、胎座重分别和葫果的长度呈极显著（P〈0．01）的幂函数正相关关系．罗布麻种群生殖分株同时具有同速和异速2种不同增减过程的表型可塑性调节．     

分子生物学数据库及相关软件的开发利用

生物大分子序列和结构测定技术的完善和应用,使核酸及蛋白质序列数据库及蛋白质结构数据库迅速增长。面对不断增长的分子生物信息,很多生物学工作者又在此基础上构建了具有特殊生物学意义和专门用途的二次数据库,使得数据库的内容和种类更加丰富和具体,为生物学各个领域的深入研究提供了坚实的信息基础。由法国生物信息研究中心Ｉｎｆｏｂｉｏｇｅｎ提供的生物数据库目录ｄｂｃａｔ〔１〕可以使用户对目前世界各地提供的分子生物信息数据库有一个详尽的了解。ｄｂｃａｔ本身也是一个具有一定数据格式的数据库,按ＤＮＡ、ＲＮＡ、蛋白质…     

水稻染色体的长度顺序和编号问题

水稻染色体形体较小, 很难从形态上区分各别染色体。尽管有许多学者报道了水稻核型的研究结果, 但不同学者之间的分歧依然存在。本文对不同学者所作核型进行了分析, 从而对现行的水稻染色体编号系统提出了新的看法。 Abstract　As rice chromosome is very small, it is difficult to identify morphologically the individual chromosome from rice chromosome complement. Although many studies have been conducted on the karyotype of rice, controversies still exist among different researchers. The present paper summerized the data of rice karyotype given by different researchers, and some suggestions were also proposed on rice chromosome numbering system.     

De novo achondroplasia causing four consecutive unsuccessful pregnancies: a case report

ABSTRACT: INTRODUCTION: The incidence of achondroplasia is very low, and the birth of two or more consecutive babies with achondroplasia to unaffected parents is a rarity. We report a rare case of recurrent achondroplasia in babies of unaffected parents. CASE PRESENTATION: A 29-year-old Nigerian Igbo woman who has had three consecutive dead achondroplastic babies presented at a gestational age of 31 weeks with a two-hour history of drainage of liquor and vaginal bleeding. Neither she nor her husband had features of achondroplasia. Fundal height was compatible with the gestational age. Fetal heart activity was present. An abdominal ultrasound examination showed a viable fetus with short long bones, oligohydramnios, and a fundal placenta with a small retroplacental blood clot. Our patient was stabilized and had an emergency Cesarean section for grade 1 abruptio placentae. A live male baby with Apgar scores of 4 at one minute and 5 at 10 minutes was delivered. The baby had classic features of achondroplasia and died shortly after birth. CONCLUSIONS: To the best of our knowledge, this is the first reported case of recurrent achondroplasia in siblings of unaffected parents in Nigeria. Management is challenging, and the outcomes of future pregnancies appear bleak. However, proper counseling and follow-up are needed. There is also a need to establish preconception clinics and facilities for prenatal genetic diagnosis and gene therapy in developing countries.