粘质沙雷氏菌氯霉素抗性基因的克隆及其性质分析

通过构建粘质沙雷氏菌KMR-3菌株的基因组DNA文库, 克隆到了与该菌的氯霉素抗性相关基因, 并对其部分特性进行了初步研究。结果表明: 克隆到的氯霉素抗性基因所编码的蛋白属于PRK10473蛋白, 由397个氨基酸编码, 与变形斑沙雷氏菌(Serratia proteamaculans 568) Bcr/CflA亚家族药物抗性转运蛋白同源性最高, 达到92%, 并对该基因的调控序列(启动子、终止子、SD序列及转录起始位点) 进行了分析。     

Phylogenetic analysis of several Thermus strains from Rehai of Tengchong, Yunnan, China

Several Thermus strains were isolated from 10 hot springs of the Rehai geothermal area in Tengchong, Yunnan province. The diversity of Thermus strains was examined by sequencing the 16S rRNA genes and comparing their sequences. Phylogenetic analysis showed that the 16S rDNA sequences from the Rehai geothermal isolates form four branches in the phylogenetic tree and had greater than 95.9% similarity in the phylogroup. Secondary structure comparison also indicated that the 16S rRNA from the Rehai geothermal isolates have unique secondary structure characteristics in helix 6, helix 9, and helix 10 (reference to Escherichia coli). This research is the first attempt to reveal the diversity of Thermus strains that are distributed in the Rehai geothermal area.     

喀斯特季节性雨林木本植物胸高断面积分布格局及其对地形因子的响应

森林生态系统地上生物量的分布格局是物种分布格局的重要内容。局域尺度内因地形差异引起的生境异质性是地上生物量分布格局形成的环境基础。本文以弄岗北热带喀斯特季节性雨林15 ha动态监测样地2011年第一次普查数据中每木个体为研究对象, 尝试以每20 m × 20 m样方内所有个体及不同径级类群的胸高断面积之和为木本植物地上生物量的衡量指标, 利用广义可加模型对喀斯特季节性雨林中胸高断面积之和的空间分布格局进行研究, 定量分析了其对7个地形因子的响应。结果表明, 洼地、山坡和山脊3种生境类型中, 所有个体的胸高断面积之和山坡最高、山脊最低, 且山脊与山坡、洼地的差异均显著; 广义可加模型结果显示, 不同地形因子对胸高断面积之和的解释偏差差异明显, 其中海拔、坡向、凹凸度、岩石裸露率对胸高断面积之和的解释偏差依次降低, 而干旱度指数、坡度和地形湿润指数解释偏差相对较小。喀斯特季节性雨林木本植物胸高断面积之和空间分布的异质性及其与地形因子之间的关系, 反映了胸高断面积之和在地形因子对土壤、水分和光照等条件重分配影响下的多重响应机制及生长策略。     

腾冲热海七株高温厌氧菌的分离及鉴定

摘要：【目的】了解中国云南腾冲热海环境中厌氧菌的分类学特征及生理生化特性。【方法】利用Hungate厌氧操作技术,从云南腾冲热海80-93℃温泉中分离出7株高温厌氧菌,对其进行形态、生长特征及16S rRNA基因序列分析,确定菌株的系统发育地位。【结果】7株菌株细胞形态均为杆状,不产芽孢,革兰氏阴性,严格厌氧,在70℃生长良好。其中较典型的菌株RH0802能在55-80℃温度范围内生长,最适生长温度为70℃;生长pH值范围为5.5-8.5,最适pH值为7.0,能利用葡萄糖、淀粉、甘露醇、甘露糖、核糖、麦芽糖、纤维二糖、木糖、果糖、半乳糖、木聚糖、甘油,不能利用蔗糖、丙酮酸。16S rRNA基因序列相似性的比较分析表明,其中5株菌与Caldanaerobacter属菌株的最高相似性均在98%以上,而RH0804与RH0806分别为96%和93%。菌株RH0802-RH0808的序列登录号分别为FJ748766、FJ748762、FJ748761、FJ748763、FJ748765、FJ748764和FJ748767,在中国普通微生物菌种保藏中心的保藏号分别为CGMCC1.5134-1.5140。【结论】分离自腾冲热海的7株嗜热厌氧菌与Caldanaerobacter属菌株有较高相似性,可将这7株菌株鉴定为Caldanaerobacter属菌株（Caldanaerobacter. sp）,其中菌株RH0804和RH0806有成为新种的可能。     

Effects of Nutrients,Temperature and Their Interactions on Spring Phytoplankton Community Succession in Lake Taihu,China

We examined the potential effects of environmental variables, and their interaction, on phytoplankton community succession in spring using long-term data from 1992 to 2012 in Lake Taihu, China. Laboratory experiments were additionally performed to test the sensitivity of the phytoplankton community to nutrient concentrations and temperature. A phytoplankton community structure analysis from 1992 to 2012 showed that Cryptomonas (Cryptophyta) was the dominant genus in spring during the early 1990s. Dominance then shifted to Ulothrix (Chlorophyta) in 1996 and 1997. However, Cryptomonas again dominated in 1999, 2000, and 2002, with Ulothrix regaining dominance from 2003 to 2006. The bloom-forming cyanobacterial genus Microcystis dominated in 1995, 2001 and 2007–2012. The results of ordinations indicated that the nutrient concentration (as indicated by the trophic state index) was the most important factor affecting phytoplankton community succession during the past two decades. In the laboratory experiments, shifts in dominance among phytoplankton taxa occurred in all nutrient addition treatments. Results of both long term monitoring and experiment indicated that nutrients exert a stronger control than water temperature on phytoplankton communities during spring. Interactive effect of nutrients and water temperature was the next principal factor. Overall, phytoplankton community composition was mediated by nutrients concentrations, but this effect was strongly enhanced by elevated water temperatures.     

粤港澳大湾区PM2.5时空分布特征及其与气象要素的关系

细颗粒物（PM_2.5）污染不仅是现代社会城市化进程中的痛点,也是城市大气环境研究不可忽略的重要焦点。粤港澳大湾区作为世界级城市群,既是城市区域经济社会文化发展的重要体现,更是国家区域发展战略的重要构成与政策实施落脚点,其生态环境的优劣尤其受瞩目。对1999-2016年大湾区地表PM_2.5浓度栅格数据集进行了时空分布特征分析,其中空间自相关分析选取莫兰指数（Moran''I指数）作为度量;并利用多元线性回归模型探讨研究区内PM_2.5与气象要素之间关系。结果表明：粤港澳大湾区1999-2016年历年PM_2.5浓度呈先增加后减小的趋势,2008年为时间拐点,该时间节点之后空气质量显著提高,且1999、2009、2016三年,年平均PM_2.5浓度相似值趋于聚集分布。冷热点分析结果表明：热点区域集中于湾区行政核心区域范围内;冷点集中于核心边缘区域,空气质量较优。利用皮尔森相关分析最终筛选出实际蒸散量（aet）、太阳辐射（srad）、最低温度（tmmn）、蒸汽压（vap）、饱和水汽压差（vpd）、风速（ws）等6个气象因子,利用回归分析判断影响PM_2.5浓度时空分布的显著因子。结果表明：本研究区太阳辐射与PM_2.5浓度关系呈负相关,该结果与其他城市相关研究有较大差异,最小温度与PM_2.5浓度呈正相关,风速与PM_2.5浓度呈负相关,饱和水气压差与PM_2.5浓度呈正相关。     

裂解或溶源-细菌遭遇噬菌体后的命运抉择

噬菌体是地球上数量最丰富的有机体,其在自然生态系统的塑造和细菌进化驱动中发挥着至关重要的作用。在与宿主的相互斗争中,噬菌体可以选择以下2种方式决定其与宿主的命运:(1)裂解:通过裂解宿主细胞最终大量释放噬菌体颗粒;(2)溶源:将其染色体整合到宿主细胞基因组中,与宿主建立一种潜在的互存关系。对于一些温和的噬菌体,这种倾向进一步受到感染多样性的调节,其中单一感染主要是裂解性的,而多重感染则多是溶源性的。溶源性的噬菌体不仅可以根据外界环境的理化因子,还可以通过细菌自身的群体感应系统来启动裂解-溶源开关,进而决定其宿主菌的命运。与此同时,宿主细菌在与噬菌体长时间的斗争中也进化出了针对噬菌体的手段。总而言之,噬菌体深刻影响着细菌的群落动态、基因组进化和生态系统等,而这一切都取决于噬菌体与宿主间的斗争模式(裂解/溶源性感染)。本文探讨了导致温和噬菌体对宿主菌进行裂解-溶源命运抉择的影响因素并系统性总结了细菌在面对噬菌体侵染时的应对策略的最新研究进展,以期能为噬菌体与宿主的研究提供建议和帮助。     

A novel malic enzyme gene, <Emphasis Type="Italic">Mime2</Emphasis>, from <Emphasis Type="Italic">Mortierella isabellina</Emphasis> M6-22 contributes to lipid accumulation

Objective

This study was aimed at cloning and characterizing a novel malic enzyme (ME) gene of Mortierella isabellina M6-22 and identifying its relation with lipid accumulation.

Methods

Mime2 was cloned from strain M6-22. Plasmid pET32aMIME2 was constructed to express ME of MIME2 in Escherichia coli BL21. After purification, the optimal pH and temperature of MIME2, as well as K_m and V_max for NADP⁺ were determined. The effects of EDTA or metal ions (Mn²⁺, Mg²⁺, Co²⁺, Cu²⁺, Ca²⁺, or Zn²⁺) on the enzymatic activity of MIME2 were evaluated. Besides, plasmid pRHMIME2 was created to express MIME2 in Rhodosporidium kratochvilovae YM25235, and its cell lipid content was measured by the acid-heating method. The optimal pH and temperature of MIME2 are 5.8 and 30 °C, respectively.

Results

The act ivity of MIME2 was significantly increased by Mg²⁺, Ca²⁺, or Mn²⁺ at 0.5 mM but inhibited by Cu²⁺ or Zn²⁺ (p?<?0.05). The optimal enzymatic activity of MIME2 is 177.46 U/mg, and the K_m and V_max for NADP⁺ are 0.703 mM and 156.25 μg/min, respectively. Besides, Mime2 transformation significantly increased the cell lipid content in strain YM25235 (3.15?±?0.24 vs. 2.17?±?0.31 g/L, p?<?0.01).

Conclusions

The novel ME gene Mime2 isolated from strain M6-22 contributes to lipid accumulation in strain YM25235.

     

Pre-classification improves relationships between water clarity, light attenuation, and suspended particulates in turbid inland waters

Relationships between water clarity, light attenuation, and concentration of suspended particulates are important in water optics and remote sensing, but are not well described yet, especially for optically complex turbid inland waters. In this study, based on 3-year data from Chinese lakes (Lake Taihu, Lake Chaohu, and Three Gorges reservoir), we propose a new approach to describe the inter-relationships of these bio-optical variables. This approach includes a pre-classification step of the waters into three types based on a semi-analytical parameter C _s before establishing the relationships. Our results showed that the pre-classification of waters increased model accuracies both for Z _SD (Secchi depth) versus K _d (diffuse attenuation coefficient) and K _d versus TSM (total suspended matter concentration). The quasi-theoretical model described better the relationship between Z _SD and K _d than the empirical model. For the K _d versus TSM relationship, linear models proved suitable for the Type 2 and Type 3 waters, whereas the power function model gave a better fit for the Type 1 water. Testing of the proposed relations with an independent dataset showed mean absolute percentage errors (MAPE) mostly below 30%. The findings of this study clarify the relationships between Z _SD, K _d, and TSM, and improve our bio-optical understanding of complex turbid inland waters.     

基于宏基因组分析纳帕海高原湿地微生物及其碳氮代谢多样性

由于地理位置特殊和生态系统类型的复杂多样性,高原湿地在水源供给、温室气体调节、生物多样性保护等方面具有不可忽视的生态作用。纳帕海高原湿地是特殊的低纬度高海拔湿地类型,目前关于其微生物多样性的研究较少。文中基于宏基因组学方法对纳帕海高原湿地微生物的基因组进行测序,在细菌域中鉴定出184个门、3 262个属、24 260个种;在古菌域中检测到13个门、32个属;在真菌域中共有13个门、47个属。土壤和水体的物种多样性具有明显差异：在门水平上,土壤中酸杆菌门、变形菌门和放线菌门为优势菌门,水体则以变形菌门和拟杆菌门为主。通过宏基因组分析获得纳帕海微生物群落的多样性数据,并对高原湿地中固碳途径和氮代谢途径进行了初步分析。研究表明碳、氮代谢基因丰度较高,湿地微生物固碳途径主要以卡尔文循环、还原性三羧酸循环和3-羟基丙酸循环为主,变形菌门、绿弯菌门、泉古菌门为主要固碳菌群;对于氮循环,水中以固氮和异化硝酸盐还原过程为主,土壤则以硝化和反硝化过程为主,变形菌门、硝化螺旋菌门、疣微菌门、放线菌门、奇古菌门和广古菌门的微生物为氮循环的主要贡献者。本研究揭示的纳帕海高原湿地微生物多样性,为湿地环境的综合治理和保护提供了新的知识。