重金属Cu2+胁迫对红树植物秋茄幼苗生长及某些生理特性的影响

为揭示铜污染对红树植物的毒性效应和植物的抗性机制,作者研究了红树植物秋茄(Kandelia obovata)幼苗在不同质量浓度的Cu2+(0,0.5,5,50,100,200 mg/L)离子胁迫90 d后,幼苗生长、部分生理指标的变化以及Cu2+在幼苗体内的累积情况。测定的主要参数有:幼苗的主根长度、侧根数目、生物量、叶片的光合速率、色素含量、可溶性糖和蛋白含量及抗氧化酶系活性。研究结果表明:当Cu2+浓度范围在(0.5~200 mg/L)时,主根长度、侧根数目、生物量、叶片的光合速率、色素含量、可溶性糖和蛋白含量均呈降低趋势;根系POD活性持续升高,叶片和根系的SOD和CAT活性呈先升后降趋势;根系MDA含量在整个Cu2+胁迫浓度范围保持相对稳定,叶片MDA含量在高浓度Cu2+胁迫下增加;Cu2+主要累积在根部而向地上部分转运的较少。根据不同浓度的Cu2+离子对秋茄幼苗生长及生理特性影响,秋茄幼苗对Cu2+胁迫的耐受质量浓度范围为5~50 mg/L。     

Determinations of dimethylsulphoniopropionate (DMSP) lyase activity using headspace analysis of dimethylsulphide (DMS)

The osmolyte dimethylsulphoniopropionate (DMSP) can be enzymatically cleaved to dimethylsulphide (DMS), acrylate and a proton. The enzyme involved in this reaction is dimethylpropiothetin dethiomethylase (DMSP lyase; enzyme classification number 4.4.1.3.). Although the importance of this reaction for the global sulphur cycle, the influence of DMS on atmospheric acidity and the possible effect on climate regulation have been widely recognised, our knowledge of DMSP lyases is limited to just a few studies. Activity measurements of DMSP lyases offer an important step towards a better understanding of the conditions under which DMS is produced. In the available published data somewhat similar methods have been used before, but a critical examination of the method limitations has not been reported. To encourage further research on this enzyme, we suggest and detail two protocols for measurements of DMSP lyase activity: An in vitro assay for crude cell extracts or purified enzyme and an in vivo method for whole cells, which we recently started to use. After addition of DMSP, samples incubated in a gas tight vial may produce DMS from enzymatic cleavage under suitable conditions, and a DMS production rate can be estimated from time-series measurements of DMS in the headspace of the vial. Headspace analysis of DMS is a useful and rapid technique to estimate and compare DMSP lyase activities from different sources. The relative rates of DMS production in the liquid and of the gas transfer between liquid and headspace, determine the rate of DMS production measured via headspace analysis. If DMS production in the liquid is higher than the rate of transfer, headspace measurements will not reflect the actual amount of DMS produced in the liquid. In this case, extracts have to be diluted to a level that ensures linearity between dilution factor and reduction of enzyme activity. Additionally, incubation volumes and vials should be selected to provide a high surface-to-volume ratio to ensure maximum flux of DMS from the aqueous phase into the headspace. The methods can be adapted to further investigate species- and strain-specific activities, biogeographical distribution, cellular location and biochemical properties of various DMSP lyases.     

Involvement of anti-oxidative enzymes, photosynthetic pigments and flavonoid metabolism in the adaptation of Reaumuria soongorica to salt stress

Reaumuria soongorica is a short woody shrub widely found in semi-arid areas of China. It can survive severe environ- mental stress including high salinity in its natural habitat. Thus, we investigated the involvement of anti-oxidative enzymes, photosynthetic pigments and flavonoid metabolism in the adaptation of R. soongorica to saline environments. R. soon- gorica was treated with 0, 100, 200 and 400 mM NaC1 solutions for 14 days. Soil salt content increased significantly by watering with high content of NaC1 solution, and no variation between 8 and 14 days during treatment. The levels ofpe- roxidation of lipid membranes （measured by malondialdehyde content） and the activities of three antioxidant enzymes （superoxide dismutase （SOD）, peroxidase （POD） and ascorbate peroxidase （APX）） increased under salt stress. Chlorophyll and carotenoid content decreased with increasing salt content. The ratio of Chl a/Chl b and carotenoid/Chl exhibited sig- nificant increase under 400 mM NaC1. However, total flavonoid and anthocyanin contents and key enzyme activities in the flavonoid pathway including phenylalanine ammonialyase （PAL） and Chalcone isomerase （CHI） decreased under salt stress. These findings possibly suggest that R. soongorica has an adaptation protection mechanism against salt-induced oxidative damage by inducin~ the activity of antioxidant enzymes and maintaining a steady level of carotenoid/Chl.     

降雨量对科尔沁沙地3种沙生植物生长和生理的影响

对降水格局变化的响应是植物适应环境的重要方面。通过野外增减雨试验,研究了降水变化对科尔沁沙地3种沙生植物生长特性和生理特征的影响。结果表明：（1）6月植被平均密度最大,7月平均盖度最大,降雨量增加60%时,植被盖度最大,为58.0%。（2）增雨区的主要植物为雾冰藜（Bassia dasyphylla）和猪毛菜（Salsola collina）,减雨区主要植物为蒺藜（Tribulus terrestris）,降雨量减少60%时,蒺藜在6、7、8月密度分别为70%、80%、79%,显著高于其他植物。（3）降雨量减少时,3种沙生植物的相对含水量（RWC）减少,而细胞膜透性增加;蒺藜RWC高于雾冰藜和猪毛菜,但是丙二醛（MDA）正好相反;蒺藜的耐脱水能力和细胞膜的耐伤害程度强于雾冰藜和猪毛菜。（4）随着降雨量的增加,3种植物的光能转化效率（F_v/F_m、ΦPSⅡ）逐渐增加,但随干旱天数的增加而减小。     

Acclimatory responses to high-salt stress in Chlamydomonas (Chlorophyta, Chlorophyceae) from Antarctica

Antarctic ice microalga can survive and thrive in channels or pores containing high salinity in Antarctic ice layer. In this study, it was found that cell membrane permeability of green microalga Chlamydomonas sp. L4 from Antarctic sea ice was high in cells treated with hypersalinity due to the induction of active oxygen and radicals. However, increased super oxide dismutase (SOD) scavenged harmful free radicals effectively to keep cell membrane integrity. Also, the analysis of membrane fatty acids demonstrated the content of saturated fatty acids and monounsaturated fatty acids increased and polyunsaturated fatty acids decreased under the high-salt treatment for 14 d, which effectively reduced the membrane fluidity and minimized the injury to cell membrane. The morphological changes showed that hypersalinity induced the increase of cell volume and the consumption of starch granules. However, because of the increase in detoxification of vacuoles, electron-dense deposits and SOD activity under high-salt stress, the complete noninterference thylakoids, mitochondria and cell nucleus maintained cellular fundamental metabolism. Global-expression profiling of proteins showed eight protein spots disappeared, 18 protein spots decreased and 18 protein spots were enhanced after the high-salt shock obviously (P<0.05). One new peptide (pI 6.90; MW 51 kDa) was primarily confirmed as the processor of light reaction center protein CP43 in photosystem Ⅱ, which increased photosynthesis ability of Chlamydomonas sp. L4 treated with high salinity.     

Enzyme activities in the water column and in shallow permeable sediments from the northeastern Gulf of Mexico

The activities of extracellular enzymes that initiate the microbial remineralization of high molecular weight organic matter were investigated in the water column and sandy surface sediments at two sites in the northeastern Gulf of Mexico. Six fluorescently labeled polysaccharides were hydrolyzed rapidly in the water column as well as in permeable sediments. This result contrasts with previous studies carried out in environments dominated by fine-grained muds, in which the spectrum of enzymes active in the water column is quite limited compared to that of the underlying sediments. Extracts of Spirulina, Isochrysis, and Thalassiosira were also used to measure hydrolysis rates in water from one of the sites. Rates of hydrolysis of the three plankton extracts were comparable to those of the purified polysaccharides. The broad spectrum and rapid rates of hydrolysis observed in the water column at both sites in the northeastern Gulf of Mexico may be due to the permeable nature of the sediments. Fluid flux through the sediments is sufficiently high that the entire 1.5 m deep water column could filter though the sediments on timescales of a few days to two weeks. Movement of water through sediments may also transport dissolved enzymes from the sediment into the water column, enhancing the spectrum as well as the rate of water column enzymatic activities. Such interaction between the sediments and water column would permit water column microbial communities to access high molecular weight substrates that might otherwise remain unavailable as substrates.     

九孔鲍肠道及其养殖水体中异养细菌产酶能力的分析

2002年5月从汕尾健生鲍鱼场养殖水体和成鲍肠道中分离筛选到26株异养细菌,其中11株来自成鲍肠道,15株来自养殖水体。对它们产胞外酶的能力进行了比较分析。结果表明肠道异养细菌中有72.7%能分泌蛋白酶、淀粉酶或明胶酶,9.1%分泌脂肪酶,45.5%分泌卵磷脂酶;水体异养细菌中则有46.7%能分泌蛋白酶或脂肪酶,66.7%分泌卵磷脂酶、淀粉酶或明胶酶。比较发现,肠道中脂肪酶或卵磷脂酶生产菌的比例小于水体异养细菌的比例;而蛋白酶、淀粉酶或明胶酶生产菌的比例却高于水体中异养细菌的比例。另外,水体异养细菌分泌多种胞外酶的能力强于肠道异养细菌。由此揭示现有鲍鱼肠道菌群结构的不完善,进而为通过添加有益菌而提高鲍鱼饲料利用率提供了可能。     

3种致病弧菌感染对大黄鱼7种酶活性的影响

大黄鱼溃疡病主要由3种致病弧菌引起:溶藻弧菌Vibrio alginolyticus、哈维弧菌V. harveyi和副溶血弧菌V. parahaemolyticus。为了解大黄鱼抗病原菌感染的免疫反应机理,对其疾病防御提供重要的理论基础,本实验将健康的大黄鱼随机分为3个实验组和1个对照组,分别注射0.2 mL的哈维弧菌、溶藻弧菌、副溶血弧菌及灭菌生理盐水。在人工感染后的第0,1,2,4,7,10,13,16,20天分别采样,通过测定每组大黄鱼血清中7种免疫相关酶活性,比较这3种致病弧菌对大黄鱼影响的差异性。结果表明:在感染后的1～10 d,实验组大黄鱼血清中血清溶菌酶(LSZ)、酸性磷酸酶(ACP)、过氧化物酶(POD)、髓过氧化物酶(MPO)的活性变化,总体表现为先升高、后降低再逐渐升高最后趋于-致的现象,且不同病原菌之间存在-定的时效差异。 碱性磷酸酶(AKP)对入侵体内的哈氏弧菌反应较敏感,ACP、POD和MPO对溶藻弧菌反应较敏感,LSZ和PO对副溶血弧菌反应较敏感。     

Enzyme variation in marine and estuarine populations of a mud crab,Macrophthalmus hirtipes (Ocypodidae)

Protein and enzyme variation in 2 populations of the mud crab Macrophthalmus hirtipes (Jacquinot, 1853) (Ocypodidae) from 1 marine and 1 estuarine habitat were investigated by poly‐acrylamide gel electrophoresis. A survey of 24 loci revealed that 22 were common to both populations; 20 were monomorphic and 2 were highly polymorphic. Two alleles were detected for each of the polymorphic loci, esterase‐2 (EST‐2) and ester‐ase‐3 (EST‐3). The frequencies of the EST‐3 alleles were similar in the 2 populations. However, the frequencies of the 2 EST‐2 alleles in the estuarine population were significantly different from those for the marine population. Expression of 1 locus, esterase‐4 (EST‐4) was confined to the estuarine population. Two alkaline phosphatase loci (AKPH‐1 and AKPH‐2) were detected in the estuarine population, but only AKPH‐1 was found in the marine population. EST‐4 and AKPH‐2 were neither sex nor age specific. These interpopulational genetic differences may reflect differences in environmental conditions measured between the 2 habitats.