低聚羧甲基壳聚糖的抗氧化性能

将低聚壳聚糖(chitosan oligosaccharide,COS)醚化得到O-羧甲基壳聚糖(O-carboxymethyl chito-sanolig osaccharide,O-CMCOS)和N-羧甲基壳聚糖(N-carboxymethyl chitosanolig osaccharide,N-CMCOS),其取代度(substituting degree,DS)均为0.54,用红外光谱对其结构进行表征。同时,考察了其结构对超氧阴离子的清除活性以及还原能力。结果表明,COS及其衍生物清除超氧阴离子的活性及还原能力的强弱顺序均为:O-CMCOSCOSN-CMCOS。     

样品保藏方式与时间对海洋底栖细菌及原生生物荧光计数效能的影响

DAPI荧光染色技术已广泛应用于浮游细菌及原生生物的定量研究,但对底栖生物的定量效能尚缺必要的研究。比较了冷冻和冷藏两种保藏方式以及保存时间对DAPI荧光计数底栖细菌、蓝细菌、硅藻、不同粒级自养小鞭毛虫(PNF)和异养小鞭毛虫(HNF)的影响。对黄海冷水团三个站位表层2cm底栖样品进行的4℃冷藏与?20℃冷冻避光保存的比较研究表明,两种保藏方式下两个站位的所有研究对象均无显著差异,但另一站位的PNF(2~5μm和5~10μm)的冷藏保存显著优于冷冻保存。对选取的另外两个站位(0~2cm和2~5cm分层)的样品经1个月和4个月冷藏保存后的分析表明,对于底栖细菌、蓝细菌、PNF(5~10 μm)、PNF(10 μm)、HNF(10 μm)和硅藻在保存1个月和4个月后的计数没有显著差异,而对于PNF(2～5 μm)、HNF(2～5 μm)、HNF(5～10 μm)保存4个月的数量明显低于保存1个月的样品,如其中一个站位的0～2cm分层的PNF(2～5 μm)丰度减少了47.4%,2～5cm分层的丰度减少了59.6%,HNF(2～5 μm)和HNF(5～10 μm)经4个月后丰度降为0。本研究表明,对底栖细菌、蓝细菌以及原生生物的定量计数可因样品、保藏方式及保存时间的不同而产生差异,因此对于底栖样品短期内宜采用避光、冷藏保存,并在带回实验室后尽快分析。     

去极化方法测定海水的氧化还原电位初探

采用去极化法测量氧化还原标准溶液——醌氢醌标准溶液,初步探讨了去极化法测定氧化还原电位的准确度,结果发现运用去极化方法测定氧化还原电位是一种快速、准确的方法,相对传统方法而言,具有测量时间短、测量精度高、数据重现性好的优点。进一步开展去极化方法测定海水氧化还原电位,为海洋氧化还原电位的快速测量提供依据。     

长江口及毗邻海域粪大肠菌和细菌总数在夏秋季的变化

2005年夏、秋季对长江口及毗邻海域(长江口、杭州湾和舟山海域)进行了粪大肠菌群和细菌总数的调查研究,并分析了近10年来的变化趋势,结果表明:夏季长江口及毗邻海域表层水体分大肠菌数平均值20个/L,仅长江口的西部海域粪大肠菌群数量在40~80个/L之间,其余海域基本未检出;秋季表层水体粪大肠菌群数量平均为101个/L,变幅范围为20~24000个/L,其中横沙一带海域存在1个数量为105个/L以上的高值区;夏季长江口及毗邻海域表层水体细菌总数平均为6.4×102cfu/mL,变幅范围为2.0×102~7.3×103cfu/mL,高值区位于舟山群岛以东海域、长江口的中北部及南部等海域,细菌总数在103cfu/mL以上;秋季表层水体细菌总数平均为4.7×103cfu/mL,明显高于夏季,变幅范围为1.3×103~1.8×104cfu/mL,高值区主要出现在长江口东南部、杭州湾西部、舟山海区的中北部等海域,细菌总数在104~105cfu/mL之间;1996—2005年期间,全海域及各海区粪大肠菌群数量在1999年均达到最高,然后逐渐下降,在1996—1999年间海域的细菌数量呈明显的上升趋势,2000年以后数量逐渐减少,估计与海域的有机污染程度下降有关。     

墨西哥湾南部晚侏罗纪主力烃源岩的形成条件

通过对墨西哥湾不同时代可采储量的分布特征和油源对比资料的分析认为,晚侏罗纪烃源岩是墨西哥湾南部最主要的烃源岩。资料显示,晚侏罗纪优质烃源岩形成的主控因素是稳定的构造和沉积条件以及超咸的还原环境,其中,"世界顶级"的晚侏罗纪提塘阶烃源岩主要形成于超咸的碳酸盐岩和/或蒸发岩沉积环境,属半深海还原环境,有机质以藻类为主,推测烃源岩中的有机质可能与极端干旱气候条件下的藻类勃发有关。     

粤东深澳湾养殖区域异养细菌和弧菌的动态分布

调查于2007年1月至2008年12月进行,对异养细菌和弧菌丰度的时间和空间分布开展了相关的研究,结果显示深澳养殖海湾水体中以上2种被调查菌类的丰度全年变化范围分别为1.20×105―1.27×108cfu·L-1和1.00×103―3.90×105cfu·L-1;底质中的丰度变化范围分别为2.73×104―4.06×107cfu·g-1和3.25×102―7.23×104cfu·g-1.从时间上来看,营养盐类与异养细菌的相关性要强于温度、盐度、pH值和溶氧等物理因素的相关性;而弧菌与物理因素的相关性要强于与营养盐类的相关性.从空间分布来看水体环境的变化要比底质的大,水体中经常出现异养细菌和弧菌丰度的剧烈变化,变化程度也远远高于底质中细菌的变化.而且不同的养殖活动也会很明显地影响异养细菌和弧菌的丰度:S3站位水体中异养细菌的丰度比底质中的高;S5站位的底质中异养细菌和弧菌的丰度都是较高的.龙须菜的养殖可以很明显地改善底质环境,特别是降低底质中对养殖和水质环境有很大负面影响的生物和非生物因子如硫化物和弧菌等.     

拮抗香蕉枯萎病菌海洋细菌的筛选和鉴定

从93份中国南部海域近海海泥样品中分离出1800多株海洋细菌,以对峙培养法,测定海洋细菌对香蕉枯萎菌的拮抗作用,再以琼脂划线培养法(agar streak)测定菌株的抑菌活性,结果表明:约55.6%的菌株对香蕉枯萎菌有一定的拮抗作用,其中58株菌株抑制香蕉枯萎菌生长所形成的抑菌带宽度大于10.0mm,抑菌作用较好,复筛后其中13个菌株形成的抑菌带宽在15.0mm以上。经反复转接和对峙培养,筛选出拮抗效果好、抑菌活性稳定的菌株TC-1,初步鉴定为芽孢杆菌属的细菌,TC-1对14种病原微生物都有较好的抑菌效果。     

黄海冷水团海域微型异养鞭毛虫对异养细菌和蓝细菌摄食作用的初步研究

2006年10月在黄海冷水团海域的三个站点开展了微型异养鞭毛虫、异养细菌和蓝细菌的密度和生物量调查,进行了微型异养鞭毛虫的现场摄食实验,通过荧光标记细菌法和消化系数法获得该海区微型异养鞭毛虫对异养细菌和蓝细菌的摄食率,并估算了微型异养鞭毛虫对异养细菌和蓝细菌现存量及生产力的摄食压。结果显示,微型异养鞭毛虫、异养细菌和蓝细菌的密度分别为0.36×103~1.13×103,0.39×106~1.13×106和0.04×104~3.74×104cells/cm3,温跃层以上明显高于底层。微型异养鞭毛虫对异养细菌的摄食率为5.33~14.89个/(HF·h),对蓝细菌的摄食率为0.26×102~23.10×10-2cells/(HF·h),摄食率随深度而下降。微型异养鞭毛虫每天能消耗9.27%~33.08%的异养细菌现存量和8.12%~16.09%的蓝细菌现存量。同时,微型异养鞭毛虫对异养细菌和蓝细菌的日摄食量各占它们生产力的2.66%~13.10%和8.12%~16.09%。研究表明微型异养鞭毛虫的摄食可能不是秋季黄海冷水团海域浮游细菌及其生产力的主归宿。     

Growth of marine bacteria and ammonium regeneration from substrates in different C: N ratios

Natural assemblages of marine bacteria were chosen in a batch culture experiments. The impact of varying nitrogen substrate concentrations and the substrate C:N ratios (C:N_S) on the bacterial C:N ratio (C:N_B), the bacterial growth efficiency (BGE) and ammonium regeneration was mainly examined. The C:N_S ratios varied from 5:1 (carbon limitation) to 40:1 (nitrogen limitation) with varying combinations of glucose and NO₃^-. The C:N_B ratio had positive relationship with the C:N_S ratio (r=0.93, n=8), whose value was 3.77 when the C:N_S ratio was 5:1 but increased to 6.47 when the C:NS ratio was 40:1. These results indicate that the C:N_B ratio is a potential diagnostic tool for determining the bacterial growth in natural waters controlled by either, carbon or nitrogen. BGE decreased with the declining nitrate concentration and negatively related to C:N_s (r=-0.51, n=8). The average value of BGE was 0.20. This value was a little lower than other reports, which could be induced by the nitrogen source used in our experiments. Finally, regeneration time of ammonium delayed with the increasing C:N_S ratio, which indicates that there were different metabolism mechanisms when bacterial growth was limited by carbon source and nitrogen source.     

A culture-dependent survey of thermophilic bacteria from hot springs in Xiamen area in China

Microbes are believed to play important roles in ecosystem function in many environments. The hot springs of Xiamen Island are close to the Xiamen Sea, and may have some characteristics different from those of inland hot springs. Microbes living in the hot springs of Xiamen may have new characteristics. However, little is known about microbial communities of hot springs close to the Xiamen Sea. A culturedependent survey of microbial population in the Xiamen hot springs was performed by using an approach combining total cellular protein profile identification and 16S rRNA gene sequencing. A total of 328 isolates of bacteria were obtained from liquid and sediment samples from the Xiamen hot springs, including neutrophilic thermophilic bacteria and moderately thermophilic acidophiles. Neutrophilic thermophilic bacteria, which grow at a temperature range of 55—90℃ including Rhodothermus marinus (Strain 1), Thermus thermophilus (Strain 2), Thermus thiopara (Strain 3), Geobacillus stearothermophilus (Strain 4), Geobacillus thermoleovorans (Strain 5), and Pseudomonas pseudoalcaligenes (Strain 6), were recovered by 2216E plates. Moderately thermophilic acidophiles, which can grow at temperatures above 50℃ and a pH range of 1.8—3.5 such as Alicyclobacillus acidoterrestris (Strain 8), Sulfobacillus acidophilus (Strain 9), and Sulfobacillus thermosulfidooxidans (Strain 10), were isolated on selective solid medium containing sulfur and Fe2+. Among these strains, Rhodothermus marinus, Thermus thermophilus and Geobacillus stearothermophilus are not only thermophiles, but also halophiles. One bacterium strain (Strain 6) shared 99% nucleotide sequence homology with Pseudomonas pseudoalcaligenes on the 16S rRNA gene sequence, but was quite different from Pseudomonas pseudoalcaligenes in biological characteristics, suggesting that it may represent a novel thermophilic species. Results indicated that various species of neutrophilic thermophiles and moderately thermophilic acidophiles were widely distributed in the Xiamen hot springs and that Rhodothermus marinus and Thermus thermophilus dominated the cultivable microbial community.