Purification and Properties of Cold-active Metalloprotease from Curtobacterium luteum and Effect of Culture Conditions on Production

Curtobacterium luteum, a gram-positive psychrotrophic bacterium, secreting an extracellular protease was isolated from the soil of Gangotri glacier, Western Himalaya. The maximum enzyme production was achieved when isolate was grown in a pH-neutral medium containing skim milk at 15oC over 120 hour. The metal ions such as Zn2+ and Cr2+ enhanced enzyme production. The specific activity of purified enzyme was 8090 u/mg after 34.1 fold purification. The 115 kD enzyme was a metalloprotease (activity inhibited by EDTA and EGTA) and showed maximum activity at 20oC and pH 7. The enzyme was active over a broad pH range and retained 84% of its original activity between pH 6–8. There was no loss in enzyme activity when exposed for 3 hours at 4oC-20oC. However, lost 65% of activity at 30oC, and was almost inactivated at 50oC, but was resistant to repeated freezing and thawing. The enzyme activity was stimulated by manganese ions; however, it was inactivated by copper ions.     

Long-term glacier monitoring at the LTER test sites Hintereisferner,Kesselwandferner and Jamtalferner and other glaciers in Tyrol: a source of ancillary information for biological succession studies

Background: Some 3% of the area of Tyrol is covered by glaciers. Since the end of the Little Ice Age, these glaciers have shrunk by about 50%, providing open ground for succession of biota. As the exposed bare ground becomes available for colonisation, pedogenesis, and primary succession, glaciological data provide important information for the analysis of chronosequences of biological succession.

Aims: This paper summarises long-term surveillance studies and provides information on annual glacier changes with a focus on the three Tyrolean LTER sites Hintereisferner, Kesselwandferner and Jamtalferner, together with two additional glaciers.

Methods: Annual changes in the length of 54 glaciers were recorded, with the first measurements made in 1891. In addition, the long-term mass balance data of five glaciers are presented. Two of these glaciers have been surveyed since 1953.

Results: Between 1901 and 2008, the temperature during the ablation season (May to September) increased by 1.7 °C (measured at one site in Vent). In the same period, winter (October to April) accumulation showed no significant trends. Measurements of length changes showed a general glacier retreat, with limited advances in the 1920s and 1980s. The mass balance measurements indicated mass losses since the 1980s at increasing rates, especially after 2000. The reaction of glaciers to the climate signal differed in timing and magnitude according to their topographic properties.

Conclusions: Although the Tyrolean glaciers have generally retreated since the end of the Little Ice Age, the magnitude and pace of advance or recession differs from glacier to glacier. This is important to consider in studies on succession of biological communities in glacier forelands     

玉龙雪山白水1号冰川退缩迹地的植被演替

运用空间代替时间,野外调查和因子分析的方法,研究了自小冰期最盛时以来的玉龙雪山白水1号冰川裸地的植被演替各个阶段的植物群落组成及其数量特征,演替过程中植被类型的变化及其解释,小冰期冰碛垄年龄的估测这3个主要内容.累计调查的55个样方中共出现91种植物,已鉴定出63个种,分属于28个科,46个属,双子叶植物居多,包括乔木、灌木和草本3种生活型的植物.通过统计分析各个演替阶段植物群落的数量特征,揭示出各个阶段植物群落的组成及其替代规律,即:在白水1号冰川末端近250a的退缩迹地上经历了裸地-草本-灌木-乔木的发展阶段.从生态位理论方面来看,这是由于不同物种的生态位及适应性都是不同的,所以构成了不同演替阶段的各自迥异的植物群落,优势种往往是那些生态位比较宽、适应性较强,能在多个演替阶段出现的物种.演替就是朝着生态位不断分化,能够最大限度利用资源的方向发展,其中物种的替代过程实质上就是在生态位不断的分化与接近,激烈的种内与种间竞争的过程中进行着的.基于此通过综合分析海螺沟与玉龙雪山的地理区位特征,气候状况,植被演替过程以及玉龙雪山地区相关的树轮方面的资料,来尝试着估测白水1号冰川小冰期终碛垄的年龄大约在170-250a之间.     

一株蜡样芽孢杆菌低温噬菌体的分离及生物学特征

目的 探索从冰川地区分离和培养低温菌噬菌体,并对其特征进行研究.方法 利用“双层平板法”从明永冰川地区分离得到一株蜡样芽孢杆菌烈性低温噬菌体(命名为MYPB41-22),并对其生物学特征进行研究.结果 宿主菌MYB41-22鉴定为Bacillus cereus菌株.噬菌体MYPB41-22在电镜下呈长六棱柱状,具一短直尾和一“衣领”状结构,无鞘.“衣领”状结构由对称的2～4个短棒状结构组成,头部具多面体立体对称结构,长55 nm,宽40 nm;尾管长约40 nm;4℃时具侵染活性,在4～37℃均可产生边缘清晰透明的噬菌斑,最佳感染温度为15℃,最适感染pH为8,最适感染复数0.1,对氯仿不敏感,基因组为双链DNA,大小约20kb.结论 衣壳蛋白分析表明MYPB41-22在52 kDa处主条带含量较高,推测可能为其重要的结构蛋白.     

Pursuing glacier retreat: genetic structure of a rapidly expanding Larix decidua population

One of the greatest threats to the long-term viability of migrating plant species is the loss of genetic diversity due to founder effects. Populations can expand as a response to climate change, but it is uncertain if long-lived plant species can maintain sufficient genetic diversity at the leading edge of migrating populations. This study uses an expanding Larix decidua population investigated along a chronosequence at landscape (350 ha) and local (0.8 ha) scales to test whether accelerated migration as a result of climate warming has the potential to intensify genetic erosion. Nine SSR markers revealed similar genetic diversity among eight sub-populations along the chronosequence (overall H(e) = 0.73; SE=0.04). Sub-populations were not genetically differentiated and all sampled individuals (N=730) formed one major genetic cluster indicating homogenizing gene flow despite spatial genetic structure (SGS) up to 80 m. At the local scale, individuals at the leading edge [early successional sub-population (ESSP), N =140] and a sub-population at equilibrium [late successional sub-population (LSSP), N = 290] revealed high genetic diversity in largest-sized cohorts. SGS among juveniles occurred up to 30 m in LSSP but there was no structure in ESSP. Accordingly, a maximum likelihood paternity assignment revealed local gene dispersal in LSSP (2-48 m) and intermediate-to-long distance dispersal into ESSP (115-3132 m). The findings indicate intensive mixing of the genes in this expanding population instead of founder effects and support the view that genetic diversity can be maintained in a long-lived species during rapid population expansion driven by climate warming.     

贡嘎山冰川退缩区植物-土壤反馈与植物间相互作用

植物-土壤反馈是揭示陆地生物群落动态变化的关键环节,为理解植物间相互作用及植被群落变化过程奠定基础。本研究以贡嘎山冰川退缩区原生演替早(5~10年)、中(30~40年)和晚期(80~100年)3个阶段典型土壤以及各阶段优势植物为对象,采用盆栽控制试验,比较优势植物在不同土壤条件下的生物量,并量化植物间相互作用以及植物-土壤反馈的方向与强度,为探究贡嘎山冰川退缩区植被群落演替规律提供依据。结果表明:(1)植物-土壤反馈作用显著影响植物在本土中的生物量,早期沙棘(Hippophae rhamnoides)在本土中生长最差,沙棘的植物-土壤反馈系数为负值;演替中期冬瓜杨(Populus purdomii)的反馈系数趋于零;晚期峨眉冷杉(Abies fabri)在本土中生长最好,峨眉冷杉的反馈系数为正值。(2)混种时,早期沙棘与演替中、晚期植物间相互作用指数为负值;中期冬瓜杨、川滇柳(Salix rehderiana)与演替早、晚期植物的相互作用指数接近于零,晚期植物峨眉冷杉、麦吊云杉(Picea brachytyla)与演替早、中期植物相互作用指数为正值。从植物-土壤反馈的方向来看,贡嘎山植被演替从早期负反馈,中期中性反馈,过渡到晚期正反馈。此外,演替早期沙棘促进演替中晚期植物生长,演替中期冬瓜杨、川滇柳对演替早晚期植物无显著影响,晚期峨眉冷杉、麦吊云杉更利于与演替早中期植物相互竞争。结果显示,植物-土壤反馈与植物间相互作用共同驱动了贡嘎山冰川退缩区植被快速演替,直至顶极群落。     

Microbial assemblages reflect environmental heterogeneity in alpine streams

Alpine streams are dynamic habitats harboring substantial biodiversity across small spatial extents. The diversity of alpine stream biota is largely reflective of environmental heterogeneity stemming from varying hydrological sources. Globally, alpine stream diversity is under threat as meltwater sources recede and stream conditions become increasingly homogeneous. Much attention has been devoted to macroinvertebrate diversity in alpine headwaters, yet to fully understand the breadth of climate change threats, a more thorough accounting of microbial diversity is needed. We characterized microbial diversity (specifically Bacteria and Archaea) of 13 streams in two disjunct Rocky Mountain subranges through 16S rRNA gene sequencing. Our study encompassed the spectrum of alpine stream sources (glaciers, snowfields, subterranean ice, and groundwater) and three microhabitats (ice, biofilms, and streamwater). We observed no difference in regional (γ) diversity between subranges but substantial differences in diversity among (β) stream types and microhabitats. Within‐stream (α) diversity was highest in groundwater‐fed springs, lowest in glacier‐fed streams, and positively correlated with water temperature for both streamwater and biofilm assemblages. We identified an underappreciated alpine stream type—the icy seep—that are fed by subterranean ice, exhibit cold temperatures (summer mean <2°C), moderate bed stability, and relatively high conductivity. Icy seeps will likely be important for combatting biodiversity losses as they contain similar microbial assemblages to streams fed by surface ice yet may be buffered against climate change by insulating debris cover. Our results show that the patterns of microbial diversity support an ominous trend for alpine stream biodiversity; as meltwater sources decline, stream communities will become more diverse locally, but regional diversity will be lost. Icy seeps, however, represent a source of optimism for the future of biodiversity in these imperiled ecosystems.     

冰川两种藓在超低温胁迫与恢复生长状态下叶肉细胞的超微结构

为了探讨高寒冰缘区的藓类植物在超微水平的抗寒机制,该文对一号冰川下不同基质两种藓类植物水中土生的金黄银藓(Anomobryum auratum)和岩面土生的刺叶墙藓(Tortula desertorum)在常温、超低温胁迫和经胁迫后的恢复状态的超微结构进行对比。结果表明:室温下藓类植物叶肉细胞结构完整、清晰。-80 ℃超低温胁迫处理后叶肉细胞的超微结构的变化为两种藓类植物叶肉细胞大多数未出现质壁分离,但会出现质壁结构模糊,细胞质收缩; 细胞器遭到破坏甚至解体的情况; 淀粉粒、脂滴和液泡数量大大增加。在室温恢复过程中,线粒体数量增加,各个细胞器结构比超低温胁迫状态下完整性增加。根据该文的亚显微结构的分析推测这些变化是为了适应细胞迅速恢复生理功能,-80 ℃超低温胁迫没有完全使藓类植物丧失生理功能,还可以进行恢复。岩面土生刺叶蔷藓的叶细胞胞壁厚度为1 100～1 300 nm,大于水中土生金黄银藓的叶细胞胞壁厚度(200～700 nm),刺叶墙藓叶细胞胞壁比金黄银藓更厚,分析推断刺叶墙藓细胞器的抗胁迫能力也更强。综上结果表明:一号冰川的这两种藓类植物抗寒能力极强,它们独特的抗寒机制不仅与超微结构下植物淀粉粒、细胞器的结构和功能完整有关,还与其生境有关。     

Potential feedback mediated by soil microbiome response to warming in a glacier forefield

Mountain glaciers are retreating at an unprecedented rate due to global warming. Glacier retreat is widely believed to be driven by the physiochemical characteristics of glacier surfaces; however, the current knowledge of such biological drivers remains limited. An estimated 130 Tg of organic carbon (OC) is stored in mountain glaciers globally. As a result of global warming, the accelerated microbial decomposition of OC may further accelerate the melting process of mountain glaciers by heat production with the release of greenhouse gases, such as carbon dioxide (CO₂) and methane. Here, using short‐term aerobic incubation data from the forefield of Urumqi Glacier No. 1, we assessed the potential climate feedback mediated by soil microbiomes at temperatures of 5°C (control), 6.2°C (RCP 2.6), 11°C (RCP 8.5), and 15°C (extreme temperature). We observed enhanced CO₂‐C release and heat production under warming conditions, which led to an increase in near‐surface (2 m) atmospheric temperatures, ranging from 0.9°C to 3.4°C. Warming significantly changed the structures of the RNA‐derived (active) and DNA‐derived (total) soil microbiomes, and active microbes were more sensitive to increased temperatures than total microbes. Considering the positive effects of temperature and deglaciation age on the CO₂‐C release rate, the alterations in the active microbial community structure had a negative impact on the increased CO₂‐C release rate. Our results revealed that glacial melting could potentially be significantly accelerated by heat production from increased microbial decomposition of OC. This risk might be true for other high‐altitude glaciers under emerging warming, thus improving the predictions of the effects of potential feedback on global warming.     

Blue carbon gains from glacial retreat along Antarctic fjords: What should we expect?

Rising atmospheric CO₂ is intensifying climate change but it is also driving global and particularly polar greening. However, most blue carbon sinks (that held by marine organisms) are shrinking, which is important as these are hotspots of genuine carbon sequestration. Polar blue carbon increases with losses of marine ice over high latitude continental shelf areas. Marine ice (sea ice, ice shelf and glacier retreat) losses generate a valuable negative feedback on climate change. Blue carbon change with sea ice and ice shelf losses has been estimated, but not how blue carbon responds to glacier retreat along fjords. We derive a testable estimate of glacier retreat driven blue carbon gains by investigating three fjords in the West Antarctic Peninsula (WAP). We started by multiplying ~40 year mean glacier retreat rates by the number of retreating WAP fjords and their time of exposure. We multiplied this area by regional zoobenthic carbon means from existing datasets to suggest that WAP fjords generate 3,130 tonnes of new zoobenthic carbon per year (t zC/year) and sequester >780 t zC/year. We tested this by capture and analysis of 204 high resolution seabed images along emerging WAP fjords. Biota within these images were identified to density per 13 functional groups. Mean stored carbon per individual was assigned from literature values to give a stored zoobenthic Carbon per area, which was multiplied up by area of fjord exposed over time, which increased the estimate to 4,536 t zC/year. The purpose of this study was to establish a testable estimate of blue carbon change caused by glacier retreat along Antarctic fjords and thus to establish its relative importance compared to polar and other carbon sinks.