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Paludicola psychrotolerans gen. nov., sp nov., a novel psychrotolerant chitinolytic anaerobe of the family Ruminococcaceae
No full textA psychrotolerant chitinolytic bacterium, designated NC1253(T), was isolated from Zoige wetland on the Qinghai-Tibetan Plateau. This strain was a Gram-stain-positive, spore-forming and rod-shaped anaerobe. NC1253(T) grew at 4-35 degrees C, at pH 6.0-8.5 and could grow on chitin as the only carbon resource. Phylogenetic analysis, based on the 16S rRNA gene sequence, showed that strain NC1253(T) represented a novel bacterial genus within the family Ruminococcaceae. Strain NC1253(T) has less than 91.0% similarity with other type strains, such as Harryflintia acetispora V20-281a(T) (90.9 %), Clostridium methylpentosum DSM 5476(T) (90.8 %), Anaerotruncus colihominis DSM 17241(T) (89.8 %), Eubacterium siraeum DSM 15702 T (89.6 %), and Acetanaerobacterium elongatum Z7(T) (89.6 %). The major components of the cellular fatty acids were iso-C14 : 0, anteiso-C15 : 0, C16 : 0 and anteiso-C17 : 0. The genomic DNA G+C content was 35.4 mol%. Phenotypic, chemotaxonomic and phylogenetic characteristics allowed strain NC1253(T) to be clearly distinguished from genera in the family Ruminococcaceae. On the basis of polyphasic taxonomic data, the isolate is considered to represent a novel genus and novel species in the family Ruminococcaceae, for which the name Paludicola psychrotolerans gen. nov., sp. nov., is proposed. The type species is NC1253(T) (DSM 104738(T) = KCTC 15582(T))
Improvement of iturin A production in Bacillus subtilis ZK0 by overexpression of the comA and sigA genes
No full textBacillus subtilis ZK0, which was isolated from cotton, produces a type of lipopeptide antibiotic iturin A that inhibits the growth of pathogenic fungi on agricultural crops. However, the low level of iturin A production by B. subtilis ZK0 does not support its large-scale application. In this study, B. subtilis ZK0 was subjected to genetic manipulation to improve iturin A production. By the independent or simultaneous overexpression of two regulatory genes (comA and sigA), iturin A production by B. subtilis ZK0 was significantly increased. When both genes were simultaneously overexpressed under optimal conditions, iturin A production increased up to 215mgl(-1) (an approximate 43-fold increase compared with B. subtilis ZK0). Moreover, overexpression of both genes was unexpectedly found to inhibit biofilm formation by B. subtilis ZK0, indicating that the phenomenon of stuck fermentation' would be avoided during B. subtilis ZK0 fermentation. In conclusion, a genetic manipulation method that improves iturin A production and inhibits biofilm formation in B. subtilis ZK0 is reported for the first time and this method has the potential to be widely applied in B. subtilis ZK0 commercial fermentation. Significance and Impact of the StudyThis study provides new perspectives on improving iturin A production by Bacillus subtilis. Our newly engineered strains could be applied to commercial fermentation by enhancing yields of iturin A and reducing the rate of stuck fermentation'. Increased production would facilitate more widespread application of this powerful antibiotic
Cometabolic degradation of chloramphenicol via a meta-cleavage pathway in a microbial fuel cell and its microbial community
No full textThe performance of a microbial fuel cell (MFC) in terms of degradation of chloramphenicol (CAP) was investigated. Approximately 84% of 50 mg/L CAP was degraded within 12 h in the MFC. A significant interaction of pH, temperature, and initial CAP concentration was found on removal of CAP, and a maximum degradation rate of 96.53% could theoretically be achieved at 31.48 degrees C, a pH of 7.12, and an initial CAP concentration of 106.37 mg/L. Moreover, CAP was further degraded through a ring-cleavage pathway. The antibacterial activity of CAP towards Escherichia coli ATCC 25922 and Shewanella oneidensis MR-1 was largely eliminated by MFC treatment. High-throughput sequencing analysis indicated that Azonexus, Comamonas, Nitrososphaera, Chryseobacterium, Azoarcus, Rhodococcus, and Dysgonomonas were the predominant genera in the MFC anode biofilm. In conclusion, the MFC shows potential for the treatment of antibiotic residue-containing wastewater due to its high rates of CAP removal and energy recovery. (C) 2017 Elsevier Ltd. All rights reserved
Gut microbiota may predict host divergence time during Glires evolution
No full textThe gut microbial communities of animals play key roles in host evolution. However, the possible relationship between gut microbiota and host divergence time remains unknown. Here, we investigated the gut microbiota of eight Glires species (four lagomorph species and four rodent species) distributed throughout the Qinghai-Tibet plateau and Inner Mongolia grassland. Lagomorphs and rodents had distinct gut microbial compositions. Three out of four lagomorph species were dominated by Firmicutes, while rodents were dominated by Bacteroidetes in general. The alpha diversity values (Shannon diversity and evenness) exhibited significant differences between any two species within the lagomorphs, whereas there were no significant differences among rodents. The structure of the gut microbiota showed significant differences between lagomorphs and rodents. In addition, we calculated host phylogeny and divergence times, and used a phylogenetic approach to reconstruct how the animal gut microbiota has diverged from their ancestral species. Some core bacterial genera (e.g. Prevotella and Clostridium) shared by more than nine-tenths of all the Glires individuals associated with plant polysaccharide degradation showed marked changes within lagomorphs. Differences in Glires gut microbiota (based on weighted UniFrac and Bray-Curtis dissimilarity metrics) were positively correlated with host divergence time. Our results thus suggest the gut microbial composition is associated with host phylogeny, and further suggest that dissimilarity of animal gut microbiota may predict host divergence time
Big data analysis of status and trends of global change research
No full text采用大数据方式,通过对Web of Science核心平台全球变化研究数据进行文献采集、存储、挖掘和关联分析,探究全球变化领域的研究趋势、研究力量、学科布局以及领域的重点与热点。该领域在此平台共检索到145 849篇论文,年发文量总体呈快速增长趋势。美国在发文量、总被引频次上远远超过其他国家,中国科学院以5 815篇发文量在所有研究机构中排第一。全球变化研究主要分布在环境科学与生态、地学、气象学与大气科学等学科。全球变暖、温室气体效应、碳氮循环、生物多样性保护、可持续发展等为该领域主要研究内容。遥感、卫星、模型、GIS等是主要研究手段
Interannual variation in methane emissions from tropical wetlands triggered by repeated El Nino Southern Oscillation
No full textMethane (CH4) emissions from tropical wetlands contribute 60%-80% of global natural wetland CH4 emissions. Decreased wetland CH4 emissions can act as a negative feedback mechanism for future climate warming and vice versa. The impact of the El Nino-Southern Oscillation (ENSO) on CH4 emissions from wetlands remains poorly quantified at both regional and global scales, and El Nino events are expected to become more severe based on climate models' projections. We use a process-based model of global wetland CH4 emissions to investigate the impacts of the ENSO on CH4 emissions in tropical wetlands for the period from 1950 to 2012. The results show that CH4 emissions from tropical wetlands respond strongly to repeated ENSO events, with negative anomalies occurring during El Nino periods and with positive anomalies occurring during La Nina periods. An approximately 8-month time lag was detected between tropical wetland CH4 emissions and ENSO events, which was caused by the combined time lag effects of ENSO events on precipitation and temperature over tropical wetlands. The ENSO can explain 49% of interannual variations for tropical wetland CH4 emissions. Furthermore, relative to neutral years, changes in temperature have much stronger effects on tropical wetland CH4 emissions than the changes in precipitation during ENSO periods. The occurrence of several El Nino events contributed to a lower decadal mean growth rate in atmospheric CH4 concentrations throughout the 1980s and 1990s and to stable atmospheric CH4 concentrations from 1999 to 2006, resulting in negative feedback to global warming
Effects of canopy gaps on N2O fluxes in a tropical montane rainforest in Hainan of China
No full textBackground and aims: Tropical montane rainforests play an important role in increasing atmospheric N2O concentration. Although accurate estimations of N2O fluxes in tropical montane rainforests are critical for predicting global climate change, there are still considerable uncertainties about the spatial and temporal variability of the emissions. This study aims to investigate the effects of canopy gap caused by typhoons on N2O emissions, a key factor for understanding the spatial heterogeneity and supporting environmental regulations. Methods: N2O fluxes were measured monthly using static chambers both inside and outside two large canopy gaps in the tropical montane rainforest of the Jianfengling National Natural Reserve on Hainan Island, south of China, from August 2012 to July 2013. Results: Mean annual N2O emissions were 2.19 +/- 0.43 kg N2O-N ha(-1) yr(-1) inside canopy gaps, and 1.19 +/- 0.29 kg N2O-N ha(-1) yr(-1) outside canopy gaps, revealing substantial differences in N2O emissions resulting from forest structure. Moreover, N2O emission rates within canopy gaps during the wet season (2.89 kg N2O-N ha(-1) yr(-1)) were significantly higher than those during the dry season (1.34 kg N2O-N ha(-1) yr(-1)), suggesting strong regulation of soil moisture and precipitation in controlling soil N dynamics. However, there were significant nonlinear relationships between N2O fluxes and water filled pore space, and soil temperature within canopy gaps, but no significant relationships were found under the closed canopy. Conclusions: Contribution of canopy gaps should be considered to avoid underestimation of N2O emission rates from disturbed forests. Interestingly, emissions from gaps are more strongly coupled with climate drivers (moisture and temperature), with important implications for climate change projections. Therefore, the further research is needed to study the biogeochemical processes and mechanisms behind such phenomenon. (C) 2017 Elsevier B.V. All rights reserved
Qinghai–Tibetan Plateau peatland sustainable utilization under anthropogenic disturbances and climate change
No full textOften referred to as the “Third Pole,” China’s Qinghai–Tibetan Plateau developed large amounts of peatland owing to its unique alpine environment. As a renewable resource, peat helps to regulate the climate as well as performing other important functions. However, in recent years, intensifying climate change and anthropogenic disturbances have resulted in peatland degradation and consequently made sustainable development of peatland more difficult. This review
summarizes peatland ecological and economic functions, including carbon sequestration, biodiversity conservation,energy supplies, and ecotourism. It identifies climate change and anthropogenic disturbances as the two key factors attributing to peatland degradation and ecosystem carbon loss. Current problems in environmental degradation and future challenges in peatland management under the effects of global warming are also discussed and highlighted
Responses of nutrient capture and fine root morphology of subalpine coniferous tree Picea asperata to nutrient heterogeneity and competition
No full textInvestigating the responses of trees to the heterogeneous distribution of nutrients in soil and simultaneous presence of neighboring roots could strengthen the understanding of an influential mechanism on tree growth and provide a scientific basis for forest management. Here, we conducted two split-pot experiments to investigate the effects of nutrient heterogeneity and intraspecific competition on the fine root morphology and nutrient capture of Picea asperata. The results showed that P. asperata efficiently captured nutrients by increasing the specific root length (SRL) and specific root area (SRA) of first-and second-order roots and decreasing the tissue density of first-order roots to avoid competition for resources and space with neighboring roots. The nutrient heterogeneity and addition of fertilization did not affect the fine root morphology, but enhanced the P and K concentrations in the fine roots in the absence of a competitor. On the interaction between nutrient heterogeneity and competition, competition decreased the SRL and SRA but enhanced the capture of K under heterogeneous soil compared with under homogeneous soil. Additionally, the P concentration, but not the K concentration, was linearly correlated to root morphology in heterogeneous soil, even when competition was present. The results suggested that root morphological features were only stimulated when the soil nutrients were insufficient for plant growth and the nutrients accumulations by root were mainly affected by the soil nutrients more than the root morphology
鼠兔肠道微生物多样性与宿主和环境的关系
No full text要鼠兔肠道微生物多样性与宿主和环境的关系高原鼠兔是青藏高原的基石物种，它们对生态系统有着重要的功能, 包括（i）制造洞穴，能够为小型鸟类和蜥蜴提供理想的栖息地；（ii）创造了微型的栖息地，促进了植物多样性的增加；（iii）给高原上一些肉食性动物提供食物资源；（iv）促进了生态系统物质循环；（V）改变土壤的结构和透气性，增加土壤混合。但是在种群密度失去控制情况下，鼠兔可能导致草场破坏，降解或沙化，导致了牲畜的食物资源减少，不利于牲畜的放牧。高原鼠兔生活在3000m-6000m的高海拔环境，有着各种各样的生理机制适应寒冷和缺氧的高海拔环境，包括有较高的静息代谢率，无寒颤性产热以及氧气利用率，这些生理适应性需要增加有效的能量产生。而肠道微生物对植物性食物的发酵可以产生很多代谢物质，为宿主提供充足的能量。中国另外一种普遍的达乌尔鼠兔，广泛分布于海拔1000m左右的内蒙古草原，能够很好的适应低海拔环境。但是，对于这两种鼠兔的肠道微生物如何适应不同的海拔环境和食物资源还不了解。因此本文采用高通量测序技术并结合其它的生理生化测定方法，研究了鼠兔肠道微生物多样性，功能以及高海拔适应性。本研究的主要结果如下：1. 探究和比较了高原鼠兔和达乌尔鼠兔食物组成，肠道微生物组成，短链脂肪酸图谱以及纤维素酶活性的不同，发现鼠兔的肠道微生物主要的门是Firmicutes, Bacteroidetes, Proteobacteria 和Spirochaetes. 在属水平上，Prevotella, Oscillospira, Ruminococcus 和Treponema 是最优势的四个属。季节和宿主物种显著影响鼠兔肠道微生物群落结构。证明了栖息在高海拔的高原鼠兔有着更低的食物多样性，但是有更高的微生物多样性，短链脂肪酸浓度以及纤维素酶活性，从肠道微生物的角度证明了高原鼠兔比达乌尔鼠兔有着更高的食物的发酵能力，显示了肠道微生物的高海拔适应性。2. 利用DNA metabarcoding 技术，探究了三个不同海拔地区高原鼠兔的食物多样性和肠道微生物多样性的关系。我们发现食物的alpha多样性和肠道微生物的alpha多样性没有显著相关性，但是食物的beta多样性和肠道微生物的beta 多样性密切相关。这些结果显示，肠道微生物的物种数并不会随着食物种类的增加而增加，但是那些食物组成更相似的个体，肠道微生物组成也更相似。3. 比较了不同海拔鼠兔肠道微生物，植物和土壤微生物的组成，发现鼠兔肠道微生物和环境（植物和土壤）微生物显著不同，鼠兔的核心微生物不是环境中最丰富的微生物类群，鼠兔和环境中共有的微生物物种，在环境中都是稀有的类群。但是这些细菌隶属于多样化的微生物类群。从而证明了宿主选择在肠道微生物的构建中占有主要角色，宿主的肠道主要选择那些稀有但是多样化的环境微生物类群。4. 阐明了高原鼠兔种群密度和肠道微生物的关系，我们设置了不同宿主种群密度的样地。结果显示宿主种群密度和一些肠道微生物类群相关，例如Ruminococcaceae, Lachnospiraceae和Staphylococcaceae和种群密度正相关。有趣的是，宿主种群密度和肠道微生物的alpha多样性（Shannon 多样性或者物种数）正相关。比起低密度组，高密度组的个体之间肠道微生物组成和结构更加相似。宿主种群密度解释了肠道微生物组成的变异，即便控制了性别，体重，食物和地理位置。这些结果显示宿主密度是调节肠道微生物多样性的一个重要因子。5. 比较了高原鼠兔，达乌尔鼠兔和其它近缘的6个进化物种的肠道微生物组成和宿主系统进化，这8个物种包括4个兔形目物种和4个啮齿目物种，都属于啮齿总目。兔型目和啮齿目有不同的微生物群落结构。兔型目物种中Firmicutes 是最优势门，然而在大部分啮齿目物种中，Bacteroidetes 是优势类群。Alpha 多样性值在任何两个兔型目物种中都显示了显著的不同，然而大部分啮齿目物种的alpha多样性并没有显示显著的不同。另外，使用了系统进化的方法组建了肠道微生物菌群如何随着分化时间而变化。一些跟植物多糖降解相关的核心菌群，包括Prevotella 和Clostridium, 在兔型目物种中显著变化。肠道微生物的距离和宿主的分化时间正相关，显示肠道微生物可以预测宿主分化时间。这些结果为探究肠道微生物与宿主协同进化提供了重要信息