抗皮肤真菌海洋放线菌MB-98的分类鉴定

从辽宁省大连海域分离到 1株海洋放线菌 ,编号MB 98,其产生的次生代谢产物对皮肤致病真菌白色念珠菌、石膏样毛癣菌、红色毛癣菌有很好的抑制作用。MB 98在大部分特征培养基上气丝为白色或白略粉 ,基丝为炒米黄或浅芒果棕 ,在所有培养基上均无色素产生 ,电镜观察MB 98孢子丝呈稀疏螺旋型 ,孢子呈椭圆或长圆柱型 ,孢子表面光滑 ,MB 98可以利用大部分碳源。根据分类鉴定研究 ,将MB 98定名为白色链霉菌海洋变种。

Microstructure of the crystals generated in borate glass irradiated by femtosecond laser pulses

In this study, we examined the microstructure of crystals generated in borate glass by femtosecond laser irradiation (FSLI). The distribution of the high-temperature and low-temperature phases of barium metaborate crystals produced in the borate glass is analyzed using Raman spectroscopy. We then propose the possible mechanism for the generation of crystals in glass by FSLI.

Genome-wide analysis of restriction-modification system in unicellular and filamentous cyanobacteria

Cyanobacteria are an ancient group of gram-negative bacteria with strong genome size variation ranging from 1.6 to 9.1 Mb. Here, we first retrieved all the putative restriction-modification (RM) genes in the draft genome of Spirulina and then performed a range of comparative and bioinformatic analyses on RM genes from unicellular and filamentous cyanobacterial genomes. We have identified 6 gene clusters containing putative Type I RMs and 11 putative Type II RMs or the solitary methyltransferases (MTases). RT-PCR analysis reveals that 6 of 18 MTases are not expressed in Spirulina, whereas one hsdM gene, with a mutated cognate hsdS, was detected to be expressed. Our results indicate that the number of RM genes in filamentous cyanobacteria is significantly higher than in unicellular species, and this expansion of RM systems in filamentous cyanobacteria may be related to their wide range of ecological tolerance. Furthermore, a coevolutionary pattern is found between hsdM and hsdR, with a large number of site pairs positively or negatively correlated, indicating the functional importance of these pairing interactions between their tertiary structures. No evidence for positive selection is found for the majority of RMs, e. g., hsdM, hsdS, hsdR, and Type II restriction endonuclease gene families, while a group of MTases exhibit a remarkable signature of adaptive evolution. Sites and genes identified here to have been under positive selection would provide targets for further research on their structural and functional evaluations.

Genome-wide analysis of restriction-modification system in unicellular and filamentous cyanobacteria

Cyanobacteria are an ancient group of gram-negative bacteria with strong genome size variation ranging from 1.6 to 9.1 Mb. Here, we first retrieved all the putative restriction-modification (RM) genes in the draft genome of Spirulina and then performed a range of comparative and bioinformatic analyses on RM genes from unicellular and filamentous cyanobacterial genomes. We have identified 6 gene clusters containing putative Type I RMs and 11 putative Type II RMs or the solitary methyltransferases (MTases). RT-PCR analysis reveals that 6 of 18 MTases are not expressed in Spirulina, whereas one hsdM gene, with a mutated cognate hsdS, was detected to be expressed. Our results indicate that the number of RM genes in filamentous cyanobacteria is significantly higher than in unicellular species, and this expansion of RM systems in filamentous cyanobacteria may be related to their wide range of ecological tolerance. Furthermore, a coevolutionary pattern is found between hsdM and hsdR, with a large number of site pairs positively or negatively correlated, indicating the functional importance of these pairing interactions between their tertiary structures. No evidence for positive selection is found for the majority of RMs, e. g., hsdM, hsdS, hsdR, and Type II restriction endonuclease gene families, while a group of MTases exhibit a remarkable signature of adaptive evolution. Sites and genes identified here to have been under positive selection would provide targets for further research on their structural and functional evaluations.

海洋中天然高分子有机物来源、结构物片以及碎屑小生境非平衡态现象的研究

海洋高分子有机物在水生态系统中具有很重要的作用。以生化稳定性为特征的腐植质能促进生物细胞的呼吸和营养盐吸收；腐化过程使生化反应的中部分生物转化为相对的物质从而增加生态系统中有机物的稳定性；腐植质还参与液－液、液－固和气－液界面过程对许多微量元素的生物地球化学循环有很大的影响。论文首次用GDX－102树脂从硅藻代谢产物和分解产物中分离提取腐植质（EHS、DHS）以及乙醇可溶物（EES、DES）。用~1H-NMR、IR和紫外光进行结构分析并同海水腐蚀植质（HS）和乙醇可溶物（ES）进行比较。在测定~3H-NMR谱时，样品先在加有NaOD和D_2O溶液中溶解50天，结果得到结构信息十分丰富的谱图。HSEHS和DHS经碱水解后，许多小分子（如甲酸、甲醇、醋酸等）从大分子网络中释放出来，在~1H-NMR谱中出现许多离散尖峰，反映了它们前体物质的相似性。HS、EHS、和DHS都含有较多的高支链烷烃、碳水化合物和氨基酸结构及少量的芳烃和杂环化合物。另外，EHS和DHS中含有许多活性基团如腈基（可能是蛋白质、核本和卟啉的分解产物）、参键等，说明其仍处于腐植化过程中。结果表明，浮游植物分解产物和代谢产物是海水植质的重要来源。~1-NMR和IR谱表明，ES、EES和DES结构差别较大。ES和DES含有大量高支链烷烃（可能来源于藻类中的类脂化合物），而在EES中烷烃含量相对很少。ES、EES和DES具有不同类型的羰基（IR谱上的吸收峰分另为1720cm~(-1)、1750cm~(-1)、1680cm~(-1)）；另外，三者与氧、氮相连的α－碳上的质子类型也有很大不同。EES的低含量高支链烷烃（高支链烷结构不易被细菌降解）以及DES中含有复杂的降解产物组份表明它们潜在的不稳定性。海洋环境中广泛存在着松散的絮状聚合物－－海洋雪。海洋雪是光合作用过程和营养盐循环的重要场所，作为大洋中特殊微环境－－碎屑小生境具有和周围水体明显不同的生化性质，如有很高的新陈代谢活性，在海洋的物质、能量流动中起着重要作用。实验研究了碎小生境演分过程中特殊营养盐迁移过程和脱氢酶活性的变化，认为碎聚合物表面不仅有微生物群落的演替，而且存在非平衡过程的连续变化。当碎表面有机物氧化，O_2被消耗碳出现氧化还原电位梯度时，在时间分布上NO_3~-、SO_4~(2-)、CO_3~(2-) 可分别成为缺微区代谢过程的最终电子受体。而碎小生境氧化还原电位梯度的存在使一些要求不同氧化还原势的过程紧靠在一起进行，即在碎屑表面分布上存在不同的电子最终受体。具有特殊性质的碎屑小生境允许一些在周围水体中不能进行或受抑制的特殊营养盐迁移过程（如固氮、硝化、反硝化、氨化甚至发酵）在碎屑表面进行。对于碎屑小生境非平衡态过程的改变，作为一种适应，微生群落重新调节新陈代谢，在分叉点附近，脱氢酶活性增大。因此，碎屑小生境是一个时空有序的半封闭结构。论文还对碎屑小生境的涨落和稳定性机制作了探讨。