聚3-羟基丁酸酯（PHB）生物降解过程的研究

利用DS9701菌株对聚3-羟基丁酸酯(PHB)膜进行降解,对降解到不同程度的PHB膜采用扫描电子显微镜观察其表面形态结构的变化,并对其降解产物进行分析测定.结果表明,PHB的生物降解首先发生在PHB表面的非晶部分,随后结晶部分开始降解,并且降解首先发生在球晶的中心部分.DS9701菌株所产生的PHB解聚酶主要降解PHB的第二个酯键,降解产物为二聚体.     

L-lactic acid production by Lactobacillus casei fermentation with corn steep liquor-supplemented acid-hydrolysate of soybean meal

Batch and fed-batch fermentation studies were performed to evaluate the potential of corn steep liquor (CSL)-supplemented acid-hydrolysate of soybean meal (AHSM) as an alternative to yeast extract (YE) for the production of L-lactic acid by Lactobacillus casei LA-04-1. The CSL-supplemented AHSM gave an outstanding result in supporting L-lactic acid production from glucose. In the exponential fed-batch fermentation, the concentration, yield and productivity of L-lactic acid were 162.5 g/L, 89.7% and 1.69 g/L per h, respectively, which were lower than those with 20 g/L YE (180 g/L, 90.3%, 2.14 g/L per h) after 96 h of fermentation. However, the raw material cost of the nitrogen resource was estimated as only 25% of that using the YE.     

小麦中期染色体银染蛋白的分析

对小麦中期染色体中银染蛋白的大小、形状和分布频率进行图像分析,看到：染色体顺的银染蛋白以颗粒状的形式存在,其大小不同,分布不均匀,数量差异也较大;从形状来看,大的银粒为点状,小的银粒有的为点状,有的实际为短纤维状,结果表明：染色体骨架在小麦中是真实存在的,骨架蛋白以颗粒和纤维状的形式分布于整个染色体中。     

Helical Structure Revealed upon the Condensation and Decondensation of Chromosomes of Vicia faba

By using conventional and stereo electron microscopy, helical structures were revealed in prophase and telophase chromosomes of root tip cells of Vicia faba. Longitudinal and transverse sections of the chromosomes showed that both prophase and telophase chromosomes were composed of chromatin fibres about 0.5μm in diameter and among the 0.5μm chromatin fibre thinner chromatin fibres with a diameter of about 0.2μm were found. In transverse sections, prophase chromosomes appeared to be a circular structure which contained a low electron density centre encircled by the 0.5 μm fibre. In longitudinal section of the chromosomes, the 0.5 μm fibres were seen to be orientated parallel to each other while constituted roughly a right angle to the long axis of the chromosome. Helical coils consisting of the 0.5μm fibre were identified easily by stereo electron microscopy. In transverse sections of telophase chromosomes, both the circular structure similar to that of the prophase chromosomes and the hoof-shaped structure composed of the 0.5μm fibre were observed, demonstrating4 the de-spiralization of the helical coils in the decondensation of the chromosomes. Based on these observations, the radial loop. model and the multiple coiling model are discussed.     

杭州城市行道树带的繁殖鸟类及其鸟巢分布

2002年3～7月记录杭州城区24个城市行道树带中繁殖鸟类和鸟巢数量,估测或实测树带特征值,并以多元逐步回归法揭示其间关系。共记录到鸟类13种,鸟巢460个;白头鹎和集群繁殖的夜鹭、池鹭、牛背鹭的鸟巢数量占总巢数的83．9％。乌鸫、夜鹭等5种鸟倾向于在高树上筑巢,因此,整个鸟类群落的巢数随平均树高增加而增加。同样的正向联系还出现在下列变量之间：①叶高多样性与白腰文鸟和珠颈斑鸠巢数;②树冠盖度与白头鹎巢数;③树种数与珠颈斑鸠巢数;④树洞数与麻雀巢数;⑤至大片林地的距离与白腰文鸟巢数;⑥至主要水源距离与夜鹭巢数;⑦树带宽度与珠颈斑鸠巢数。另一方面,多数鸟类避免在行人容易接近的树带筑巢,而以白头鹎和珠颈斑鸠为显著。城市行道树带鸟巢的分布存在一定程度的种间差异,反映了鸟类不同的适应策略。     

隐甲藻深层培养产生二十碳五烯酸的研究

二十碳五烯酸 (Ｃ2 0 :5 ,Ｅｉｃｏｓａｐｅｎｔａｅｎｏｉｃａｃｉｄ ,简称ＥＰＡ)是一种重要的ω 3系列人体必需多不饱和脂肪酸 (Ｐｏｌｙｕｎ ｓａｔｕｒａｔｅｄｆａｔｔｙａｃｉｄｓ,ＰＵＦＡ) [1～ 2 ] 。自从Ｄｙｅｒｂｅｒｇｅ等人报道了二十碳五烯酸对防止和治疗血栓、关节硬化、抗炎症、抗癌、促进脑组织发育等方面具有明显效果以来 ,人们对它的营养和医药价值及生产方法进行了广泛的研究[3～ 6] 。目前 ,二十碳五烯酸主要来源于深海鱼油 ,但其产量不稳定 ,纯化工艺复杂且含有难以消除的鱼腥味 ,难以满足市场的需求。由于二十碳五…     

温度对不同类型早籼稻灌浆期间直链淀粉、蛋白质积累的影响

高温条件下早籼稻籽粒直链淀粉积累速率快,持续时间短;蛋白质含量高;灌浆前期谷草转氨酶和谷丙转氨酶活性高,开花11d后迅速下降．适温条件下籽粒直链淀粉积累速率慢,持续时间长;蛋白质含量低;谷草转氨酶和谷丙转氨酶活性变化缓慢,3个不同类型品种中适合作米粉的湘早籼33号直链淀粉含量最高,饲料稻湘早籼24号蛋白质含量最高．高温有助于湘早籼33号直链淀粉含量和湘早籼24号蛋白质含量的提高。     

Marine biofilm bacteria evade eukaryotic predation by targeted chemical defense

Many plants and animals are defended from predation or herbivory by inhibitory secondary metabolites, which in the marine environment are very common among sessile organisms. Among bacteria, where there is the greatest metabolic potential, little is known about chemical defenses against bacterivorous consumers. An emerging hypothesis is that sessile bacterial communities organized as biofilms serve as bacterial refuge from predation. By testing growth and survival of two common bacterivorous nanoflagellates, we find evidence that chemically mediated resistance against protozoan predators is common among biofilm populations in a diverse set of marine bacteria. Using bioassay-guided chemical and genetic analysis, we identified one of the most effective antiprotozoal compounds as violacein, an alkaloid that we demonstrate is produced predominately within biofilm cells. Nanomolar concentrations of violacein inhibit protozoan feeding by inducing a conserved eukaryotic cell death program. Such biofilm-specific chemical defenses could contribute to the successful persistence of biofilm bacteria in various environments and provide the ecological and evolutionary context for a number of eukaryote-targeting bacterial metabolites.