Bacterial response to contrasting sediment geochemistry in the Central Indian Basin

In order to investigate whether geochemical, physiographic and lithological differences in two end‐member sedimentary settings could evoke varied microbe–sediment interactions, two 25 cm long sediment cores from contrasting regions in the Central Indian Basin have been examined. Site TVBC 26 in the northern siliceous realm (10°S, 75·5°E) is organic‐C rich with 0·3 ± 0·09% total organic carbon. Site TVBC 08 in the southern pelagic red clay realm (16°S, 75·5°E), located on the flank of a seamount in a mid‐plate volcanic area with hydrothermal alterations of recent origin, is organic‐C poor (0·1 ± 0·07%). Significantly higher bacterial viability under anaerobic conditions, generally lower microbial carbon uptake and higher numbers of aerobic sulphur oxidizers at the mottled zones, characterize core TVBC 26. In the carbon‐poor environment of core TVBC 08, a doubling of the ¹⁴C uptake, a 250 times increase in the number of autotrophic nitrifiers, a four‐fold lowering in the number of aerobic sulphur oxidizers and a higher order of denitrifiers exists when compared with core TVBC 26; this suggests the prevalence of a potentially autotrophic microbial community in core TVBC 08 in response to hydrothermal activity. Microbial activity at the northern TVBC 26 is predominantly heterotrophic with enhanced chemosynthetic activity restricted to tan‐green mottled zones. The southern TVBC 08 is autotrophic with increased heterotrophic activity in the deepest layers. Notably, the bacterial activity is generally dependent on the surface productivity in TVBC 26, the carbon‐rich core, and mostly independent in TVBC 08, the carbon‐poor, hydrothermally influenced core. The northern sediment is more organic sink‐controlled and the southern sediment is more hydrothermal source‐controlled. Hydrothermal activity and associated rock alteration processes may be more relevant than organic matter delivery in these deep‐sea sediments. Thus, this study highlights the relative importance of hydrothermal activity versus organic delivery in evoking different microbial responses in the Central Indian Basin sediments.     

海洋环境中的厌氧氨氧化细菌与厌氧氨氧化作用

厌氧氨氧化是细菌在厌氧条件下将氨氮氧化成氮气的过程,主要应用在污水处理反应器中,最近几年发现在海洋环境中也广泛存在,并在海洋氮循环过程中发挥了重要作用,代表了海洋中一个巨大的氮汇,对碳循环和全球气候变化也有重要影响。梯烷膜脂结构独特,是厌氧氨氧化细菌的化学生物标志物,具有化学分类与古海洋学应用潜力。厌氧氨氧化作用及厌氧氨氧化细菌已成为海洋生物地球化学、微生物学、有机地球化学等研究领域的热点。     

长江口极微型和微微型浮游生物的垂向变化与周日波动

2006年6月12日至22日“东方红2号”考察船夏季航次期间,在长江口3个连续观测站位进行了水样采集,应用流式细胞仪分析了水样中的极微型浮游生物（Femtoplankton）和微微型浮游生物（Picoplankton）。结果显示,原绿球藻（Prochlorococcus）在所有样品中均未检测到;检测到的聚球藻（Synechococcus）和微微型真核浮游植物（Picoeukaryotes）平均丰度达数量级10^5～10^6个／L,异养细菌（Heterotrophic bacteria）和病毒（Viruses）平均丰度达数量级10^8～10^9个／L。在浑浊的长江口水域,极微型和微微型浮游生物的垂向分布特征不同,主要与各站位特有的水动力条件密切相关：浊度是调控微微型真核浮游植物、异养细菌和病毒周日变化的关键因子之一;微微型真核浮游植物成为微微型浮游植物中最重要的组成部分,与异养细菌具有显著的正相关关系。     

海岸带沉积物环境中甲烷代谢茵的富集培养及混合茵群分析

结合Hungate无氧分离技术,对海岸带沉积物中甲烷代谢菌进行了富集培养,分别为珠江口的甲烷产生菌和九龙江口的甲烷氧化菌及其他甲基氧化菌．其研究结果表明：在珠江口淇澳岛海岸带沉积物中,甲烷八叠球菌属（Methanosarcina）为优势菌株,分布于沉积物的上、中、下3个层位,并发现了部分序列与不可培养的泉古菌门（Crcnarchaeota）的杂色泉古菌（miscellaneouscrenarchaeoticgroup,MCG）的相似度为90％～99％．在九龙江口的海岸带沉积物环境中,噬甲基菌属（Methylophaga）为优势菌群,在富集产物菌群多样性中占60％～99％;还有一些相似度较低（为95％～97％）的菌群,为潜在的新种．     

Identification of a marine agarolytic bacterium Agarivorans albus QM38 and cloning and sequencing its beta-agarase genes

A total of 117 agar-decomposing cultures were isolated from coastal seawater around Qingdao,China.The phenotypic and agarolytic features of an agarolytic isolate,QM38,were investigated.The strain was gram negative,strictly aerobic,curved rod and polar flagellum.On the basis of several phenotypic characters,biochemical and morphological characters and phylogenetic analysis of the gene coding for the 16S rRNA,the strain was identified as Agarivorans albus strain QM38.This strain can liquefy the agar on the solid agar plate.An excellular agarase activity was determined in liquid culture.The enzyme exhibited maximal activity at 40℃,pH 7.6.Its activity was greatly affected by different concentrations of agarose.The highest activity 32 U/ml was achieved in the culture supernatant.The hydrolytic product was analyzed by fluorophore-assisted carbohydrate electrophoresis (FACE).After complete hydrolysis of agarose,a series of agaro-oligosaccharides were produced.The main products of the enzymes were oligosaccharides in the degree of polymerization (DP) of 2,4,6 and 8.Three genes agaD01,agaD02 and agaD03,encoding β-agarases,had been cloned from genomic DNA of Agarivorans albus strain QM38.The open reading frame of agaD01,consisted of 2 988 bp,and shared 95.5%-98.9% identity to the β-agarase genes of some strains of Vibrio and Agarivorans.Gene agaD02 comprised 2 868 bp and encoded a 955-amino-acid protein.It showed 97.4% and 98.7% identity to the β-agarase genes of strain Vibrio sp.PO-303 and strain Vibrio sp.JT0107,respectively.Only partial sequence of agaD03 gene has been cloned.It showed 96.5% identity to β-agarase gene (agaB) of Pseudoalteromonas sp.CY24,and shared 96.8% identity to β-agarase-c gene of Vibrio sp.PO-303.     

硫酸盐还原菌对热镀锌钢材氢渗透行为的影响

采用Devanathan-Stachurski 双面电解池检测氢渗透电流技术和扫描电镜分析, 研究了热镀锌钢材在灭菌海水、灭菌培养基和接种了硫酸盐还原菌(SRB)的培养基等3 种介质中的氢渗透行为。氢渗透电流检测结果表明, 培养基的部分组分对热镀锌钢材的氢渗透行为有促进作用, 试样在灭菌培养基中的氢渗透电流密度的平均值比在灭菌海水中提高了约6 倍。尽管活性SRB 代谢产生的S^2?和HS^?能够促进热镀锌钢材的氢渗透行为, 但是, 由SRB 及其代谢产物和它们所黏附的腐蚀产物所形成的致密微生物膜减少了氢的析出和试样对氢的吸收量, 导致热镀锌钢材氢渗透行为最终被抑制, 因此, 试样在接菌培养基中的氢渗透电流密度的平均值比其在灭菌培养基中降低77%。扫描电镜分析表明, 热镀锌钢材在灭菌海水中能够形成腐蚀产物膜, 而暴露于灭菌培养基中的试样表面未形成明显的腐蚀产物膜, 但在接菌培养基中试样表面能形成黏附了腐蚀产物的致密微生物膜的附着, 表明热镀锌钢材表面的微生物膜与其氢渗透行为之间存在明显的相关性。     

从养殖贝类和大菱鲆分离的海洋发光弧菌的分类地位分析

海洋发光弧菌是海水养殖中重要的条件致病菌。从福建省晋江市附近水产养殖场花蛤、牡蛎软组织及波罗地海大菱鲆肠道内含物中分离得到16 株发光细菌, 采用ARDRA（amplified ribosomal DNArestriction analysis）、16S rDNA 序列测定、Biolog 碳源代谢分析及药敏试验等方法对...     

黄河三角洲南部潮间带底栖异样细菌的分布特征研究

2008年4月和7月于黄河三角洲南部潮间带进行了大面站调查,采用DAPI荧光染色荧光显微镜计数法测定了沉积物中异养细菌数量,研究其分布特征,探讨满足其生长繁殖需要的物质来源.结果表明,春季和夏季潮间带沉积物中异养细菌丰度的变化范围分别为4.0～31.9×105 cells/g dw(平均值为11.81×105 cell...     

辽河口湿地异养细菌的变化规律及影响因素研究

通过现场调查和模拟培养实验,对辽河口湿地芦苇生长期内土壤异养细菌的变化规律及其主要影响因素进行了研究。野外现场调查结果表明,异养细菌数量6月份最多,8月份最少;植被长势良好区异养细菌数量比裸滩区高1倍左右。现场培养实验结果表明,盐分、C/N、石油、植被对异养细菌数量均有影响,异养细菌数量随盐分增加而减少;C/N比值增加,异养细菌数量明显增多,碳氮比为10∶1时,异养细菌数最大,约为对照组的3倍;石油会显著抑制异养细菌生长,浓度越高,异养细菌数量越少;有植被组的异养细菌数量明显高于无植被组。     

海洋新菌的分类与鉴定方法

细菌的分类鉴定与细菌的研究和应用有着同等重要的地位。目前从自然界中可以培养的细菌总量不到1%,大多数海洋细菌的分类鉴定仍需建立在纯培养基础上。本文对目前可培养海洋细菌的分类鉴定方法做了系统的综述,详述了系统发生树的构建,汇总了生理生化分类特征,概述了主要的遗传学分析方法,包括16S rDNA序列分析,G+C含量测定,DNA-DNA杂交,MLST(多位点序列分型,Multi Locus Sequence Typing)以及核酸指纹图谱等,并指出每种方法适用的范围以及应用时需要注意的事项。另外,本文还提出了新菌分类鉴定的一般步骤。文章最后对目前海洋细菌分类鉴定的发展趋势进行了总结和展望。