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南极冰藻Chlorophyceae L-4是南极生态系统重要的初级生产力和组成部分,其长期生长在极地环境中,有着特殊的生理机制。在生存环境和生长条件发生变化时,冰藻的膜脂系统和蛋白含量都会发生变化,而在受到重金属胁迫时,冰藻的超微结构也会发生明显变化。【目的】研究Chlorophyceae L-4在重金属离子Hg2+胁迫条件下的状态和Hg2+富集以及对其抗氧化系统的影响,为南极环境监测提供依据。【方法】绘制南极冰藻细胞在重金属离子Hg2+不同浓度胁迫条件下的生长曲线,观察其超微结构;测定丙二醛含量和SOD酶活性变化;ICP-MS法研究藻体富集Hg2+规律。【结果】Hg2+在低浓度时(≤100μg/L),细胞个数较正常条件明显偏少;在高浓度时(≥250μg/L),出现细胞死亡。丙二醛含量随Hg2+浓度升高而升高,SOD酶活性则先增强再减弱。藻体富集Hg2+在1 h达到峰值,而在Hg2+浓度持续升高时,富集量轻微降低。【结论】Hg2+离子对冰藻生长有抑制毒害作用;对Chlorophyceae L-4抗氧化系统有明显不利影响;L-4富集Hg2+在1 h内饱和,Hg2+过高时,富集量稍微降低。 相似文献
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脯氨酸和可溶性糖在南极冰藻低温适应机制中的作用 总被引:1,自引:0,他引:1
《生物技术通报》2016,(2)
对低温胁迫下两种南极冰藻胞内的脯氨酸和可溶性糖含量的变化进行分析研究,探讨两种冰藻对低温的适应性机制。测定不同培养温度和培养时间下两种南极绿藻细胞中的脯氨酸和可溶性糖含量,获得其在低温下随温度和胁迫时间变化的趋势,分析其产生变化的原因。结果显示,温度越低,塔胞藻Pyramidomonas sp.L-1胞内的脯氨酸和可溶性糖含量增加越明显。-5℃,培养48 h后,脯氨酸含量是初始值的6.5倍,可溶性糖含量增加60%。衣藻Chlamydomonas sp.L-4胞内脯氨酸的含量同样为温度越低,胞内脯氨酸的含量越高;但随时间变化趋势与塔胞藻Pyramidomonas sp.L-1相反,含量随温度作用时间的增加出现减少的趋势。-5℃,48 h后脯氨酸含量基本维持不变,可溶性糖含量增幅达90%。结果表明,脯氨酸和可溶性糖在南极冰藻的低温适应性机制中具有重要的作用,但在不同藻种中的作用机制不同。 相似文献
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南极硅藻在南极生态系统中起着至关重要的作用, 是南极食物网的基石, 其物种多样性、群落结构特征直接或间接影响南极生态系统的稳定性。根据近30 年来国内、外有关南极硅藻的多样性和生物地理学研究, 综述了海冰硅藻的种类组成和分布特点, 南极湖泊硅藻的物种构成特征及附生硅藻和共生硅藻多样性的研究进展, 为南极硅藻的生物多样性研究、分子生态学研究、生物地理学研究开发和利用提供参考依据。 相似文献
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很多越冬的生物会产生抗冻蛋白,这些抗冻蛋白能够吸附到冰晶的表面改变冰晶形态并抑制冰晶的生长.抗冻蛋白在很多生物体内都被发现,不同的抗冻蛋白结构差异非常大.目前的一些研究揭示了几种抗冻蛋白的结构,并提出了抗冻蛋白与冰晶的结合模型,但是还没有一种机制能解释所有抗冻蛋白的作用机理.抗冻蛋白能被广泛的应用到农业、水产业和低温储藏器官、组织和细胞,利用转基因技术提高植物的抗冻性具有重要应用价值.而抗冻蛋白基因的表达调控则有待进一步阐明. 相似文献
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大量的海洋栖息的动物和陆地的昆虫都能产生大分子的抗冻物质,以有助于它们生存在它们的不被保护的血液和血淋巴的体液的冰点之下的温度环境中。用这些抗冻物质结合和抑制冰晶生长的非浓度相关的方式。这样它们对一旦冰晶形成后的冰的融点就没有多大的影响了,所以研究者比较确切地将这类物质描述为热滞留蛋白质,因此这些蛋白质就成了检测抗冻能力的基础。 相似文献
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南极海冰微生物在适应极端环境的长期进化过程中,获得了特殊的生理生化特性和基因表达调控机制。为了更多的了解南极微生物的逆境适应机制,以隶属南极海冰微生物典型菌属Pseudoalteromonas的ANT319为研究对象,探讨了该菌株在3%~12%的盐度梯度下的抗盐生长情况、蛋白质含量变化、细胞膜透性、丙二醛含量变化和不同盐度对菌株细胞内超氧化物歧化酶(SOD)、过氧化氢酶(CAT)和过氧化物酶(POD)3种抗氧化酶活性的影响。结果表明,此菌株的最适生长盐度为9%,随着盐度的升高,细胞内蛋白质含量升高,膜透性逐渐增加,SOD和POD的酶活性呈现先升高后降低的变化趋势,在9%盐度下达到最高,CAT活性和MDA则基本上保持不变。可见,随着盐度的增加,细胞膜逐渐受到破坏,同时生物体对盐迫作出应激反应,产生较多蛋白来清除不良因素下产生的有害活性氧,包括生物体内抗氧化酶在内的蛋白含量及其活性的增加,研究结果初步揭示了海冰细菌的耐盐机制。 相似文献
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A method to achieve controlled ice nucleation during the freeze-drying process using an ice fog technique was demonstrated
in an earlier report. However, the time required for nucleation was about 5 min, even though only one shelf was used, which
resulted in Ostwald ripening (annealing) in some of the vials that nucleated earlier than the others. As a result, the ice
structure was not optimally uniform in all the vials. The objective of the present study is to introduce a simple variation
of the ice fog method whereby a reduced pressure in the chamber is utilized to allow more rapid and uniform freezing which
is also potentially easier to scale up. Experiments were conducted on a lab scale freeze dryer with sucrose as model compound
at different concentration, product load, and fill volume. Product resistance during primary drying was measured using manometric
temperature measurement. Specific surface area of the freeze-dried cake was also determined. No difference was observed either
in average product resistance or specific surface area for the different experimental conditions studied, indicating that
with use of the reduced pressure ice fog technique, the solutions nucleated at very nearly the same temperature (−10°C). The
striking feature of the “Reduced Pressure Ice Fog Technique” is the rapid ice nucleation (less than a minute) under conditions
where the earlier procedure required about 5 min; hence, effects of variable Ostwald ripening were not an issue. 相似文献
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Antarctic Sea Ice Biota 总被引:14,自引:1,他引:13
The sea ice surrounding Antarctica provides an extensive habitatfor organisms ranging in size from bacteria to marine birdsand mammals. Historically, most of the ecological work on theice biota has focused in the nearshore land-fast ice. Only inthe last decade have there been comparable studies in the deep-waterpack ice regions. These studies have indicated that there arefundamental differences in structural and physical characteristicsof fast and pack ice thatare a result of differing physicalregimes in nearshore and oceanic regions. Other physical processesact to create heterogeneity within the ice habitat that canrange from geographic and regional scales of patchiness to apronounced vertical gradient within ice floes. The conspicuouspatternsin the distribution of the ice biota can be explained largelyby these physical processes. Over 200 species have been reported living on, in, or in associationwith Antarctic sea ice.The ice biota includes bacteria, a varietyof algae, heterotrophic protozoans and small metazoans. Thediatom assemblages are the only taxonomic group that is knownwell enough to make comparisons among the various habitats.Studies by a number of workers suggest some specific diatomassemblages along with occurrence of species that are widelydistributedin both ice and plankton. Ice may also serve as a temporaryhabitat for species that also comprise planktonic communities,so that providing a "seed population" for ice edge planktonblooms may be an important role of the ice biota. Trophic interactionsamong organisms in ice suggest that the ice assemblage is atrue community with a welldeveloped microbial food web. Theice microbial community may be an important part of the Antarcticmarine food web because large consumers from the adjacent planktonicand benthic communities appear to feed on the ice biota. 相似文献
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Eric W. Wolff 《Philosophical transactions of the Royal Society of London. Series B, Biological sciences》2013,368(1621)
Snow and ice play their most important role in the nitrogen cycle as a barrier to land–atmosphere and ocean–atmosphere exchanges that would otherwise occur. The inventory of nitrogen compounds in the polar ice sheets is approximately 260 Tg N, dominated by nitrate in the much larger Antarctic ice sheet. Ice cores help to inform us about the natural variability of the nitrogen cycle at global and regional scale, and about the extent of disturbance in recent decades. Nitrous oxide concentrations have risen about 20 per cent in the last 200 years and are now almost certainly higher than at any time in the last 800 000 years. Nitrate concentrations recorded in Greenland ice rose by a factor of 2–3, particularly between the 1950s and 1980s, reflecting a major change in NOx emissions reaching the background atmosphere. Increases in ice cores drilled at lower latitudes can be used to validate or constrain regional emission inventories. Background ammonium concentrations in Greenland ice show no significant recent trend, although the record is very noisy, being dominated by spikes of input from biomass burning events. Neither nitrate nor ammonium shows significant recent trends in Antarctica, although their natural variations are of biogeochemical and atmospheric chemical interest. Finally, it has been found that photolysis of nitrate in the snowpack leads to significant re-emissions of NOx that can strongly impact the regional atmosphere in snow-covered areas. 相似文献
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Thomas L. Kieft 《Applied microbiology》1988,54(7):1678-1681
A newly discovered form of biological ice nucleus associated with lichens is described. Ice nucleation spectra of a variety of lichens from the southwestern United States were measured by the drop-freezing method. Several epilithic lichen samples of the genera Rhizoplaca, Xanthoparmelia, and Xanthoria had nuclei active at temperatures as warm as −2.3°C and had densities of 2.3 × 106 to more than 1 × 108 nuclei g−1 at −5°C (2 to 4 orders of magnitude higher than any plants infected with ice nucleation-active bacteria). Most lichens tested had nucleation activity above −8°C. Lichen substrates (rocks, plants, and soil) showed negligible activity above −8°C. Ice nucleation-active bacteria were not isolated from the lichens, and activity was not destroyed by heat (70°C) or sonication, indicating that lichen-associated ice nuclei are nonbacterial in origin and differ chemically from previously described biological ice nuclei. An axenic culture of the lichen fungus Rhizoplaca chrysoleuca showed detectable ice nucleation activity at −1.9°C and an ice nucleation density of 4.5 × 106 nuclei g−1 at −5°C. It is hypothesized that these lichens, which are both frost tolerant and dependent on atmospheric moisture, derive benefit in the form of increased moisture deposition as a result of ice nucleation. 相似文献