Diversity of culturable actinomycetes in hyper-arid soils of the Atacama Desert,Chile

The Atacama Desert presents one of the most extreme environments on Earth and we report here the first extensive isolations of actinomycetes from soils at various locations within the Desert. The use of selective isolation procedures enabled actinomycetes to be recovered from arid, hyper-arid and even extreme hyper-arid environments in significant numbers and diversity. In some cases actinomycetes were the only culturable bacteria to be isolated under the conditions of this study. Phylogenetic analysis and some phenotypic characterisation revealed that the majority of isolates belonged to members of the genera Amycolatopsis, Lechevalieria and Streptomyces, a high proportion of which represent novel centres of taxonomic variation. The results of this study support the view that arid desert soils constitute a largely unexplored repository of novel bacteria, while the high incidence of non-ribosomal peptide synthase genes in our isolates recommend them as promising material in screening for new bioactive natural products.     

The slow—fast life style characteristics in a suite of six species of odonate larvae

• 1 The validity of the slow—fast lifestyle dichotomy proposed by Sih (1987) was tested in a suite of six odonate species from a restricted geographical area. Data on activity and microhabitat use were obtained in a laboratory study. Further necessary information on life history, macrohabitat (ephemeral‐permanent) use and vulnerability to fish predation was provided by a literature survey.
• 2 Activity was estimated as number of moves and distance moved for the six odonate larvae. Aeschna juncea, Lestes sponsa and Sympetrum danae were categorised as high‐active species, whereas Coenagrion hastulatum, Cordulia aenea and Leucorhinia dubia were categorised as low‐active species.
• 3 C. hastulatum and L. sponsa exploited microhabitats close to the water surface, C. aenea and L. dubia close to the bottom, and A. juncea and S. danae were intermediate in their water depth utilisation.
• 4 A principal component analysis of the data from the laboratory experiment and the literature survey supported the slow—fast life style dichotomy since the variables activity, macrohabitat use, life cycle length and sensitivity to fish predators were highly correlated.

     

Geodermatophilus chilensis sp. nov., from soil of the Yungay core-region of the Atacama Desert,Chile

A polyphasic study was undertaken to establish the taxonomic status of three representative Geodermatophilus strains isolated from an extreme hyper-arid Atacama Desert soil. The strains, isolates B12^T, B20 and B25, were found to have chemotaxonomic and morphological properties characteristic of the genus Geodermatophilus. The isolates shared a broad range of chemotaxonomic, cultural and physiological features, formed a well-supported branch in the Geodermatophilus 16S rRNA gene tree in which they were most closely associated with the type strain of Geodermatophilus obscurus. They were distinguished from the latter by BOX-PCR fingerprint patterns and by chemotaxonomic and other phenotypic properties. Average nucleotide identity, average amino acid identity and digital DNA–DNA hybridization values between the whole genome sequences of isolate B12^T and G. obscurus DSM 43160^T were 89.28%, 87.27% and 37.4%, respectively, metrics consistent with its classification as a separate species. On the basis of these data, it is proposed that the isolates be assigned to the genus Geodermatophilus as Geodermatophilus chilensis sp. nov. with isolate B12^T (CECT 9483^T = NCIMB 15089^T) as the type strain. Analysis of the whole genome sequence of G. chilensis B12^T with 5341 open reading frames and a genome size of 5.5 Mb highlighted genes and gene clusters that encode for properties relevant to its adaptation to extreme environmental conditions prevalent in extreme hyper-arid Atacama Desert soils.     

Early childhood sexual abuse increases suicidal intent

Childhood sexual abuse has been consistently associated with suicidal behavior. We studied suicide attempt features in depressed individuals sexually abused as children. On average, sexual abuse started before age 9. It frequently coexisted with physical abuse. Suicide attempters more often had personality disorders and had endured abuse for longer, but did not differ in terms of other clinical characteristics from non‐attempters. Earlier onset of sexual abuse and its duration were associated with more suicide attempts. However, when personality disorders were included in the regression model, only these disorders predicted number of attempts. The severity of sexual abuse and the coexistence of physical abuse were correlated with age at first suicide attempt. However, only severity of sexual abuse was marginally associated with age at first suicide attempt in the regression model. Finally, the earlier the age of onset of sexual abuse, the higher the intent, even after controlling for age, sex and personality disorders. This suggests that the characteristics of childhood sexual abuse, especially age of onset, should be considered when studying the risk for suicidal behavior in abused populations.     

古尔班通古特沙漠植物种子大小变异的空间格局

在古尔班通古特沙漠70个固定样地中采集了87种植物种子,通过测量种子百粒重,分析了种子大小在不同分类群中的变异规律,并调查了样地中不同类型种子总数目的空间格局。结果发现:1)古尔班通古特沙漠植物种子大小可分为:A(0.1—1 mg)、B(1—10 mg)、C(10—100 mg)、D(100—1000 mg)、E(1000—5000 mg)5种类型。拥有不同类型物种数量差异较大,其中D型种子物种最多,含41种占总物种数目的 47.1%,其次C型种子30种占总物种数目的 34.5%,E型种子占总物种数的13.8%,B型种子总物种数的3.5%,A型种子占总物种数的1.1%。沙漠植物中中等种子大小物种占多数,与以色列特拉维夫以北的Poleg自然保护区地中海沿岸沙漠地区相似。由于本地属、种为地中海区、西亚至中亚分布,所以认为本沙漠种子大小主要受系统演化影响。2)科间种子大小存在极显著差异,百粒重最大科是蓼科(29315 mg)、最小的是列当科(0.3 mg)。藜科,菊科,紫草科的属间种子大小差异显著。3)生活型间种子大小差异显著,种子大小从大到小排序为:灌木类短命植物多年生草本短命植物半灌木1年生草本。4)种子大小与物种相对分布频度相关性不显著,但将相对分布频度小于1.4%的环境特化物种去除后,种子大小与物种相对分布频度呈指数型极显著负相关。5)B型、C型、D型三类种子在样地中的总数目随海拔、经度和降水的增加而极显著增加,随纬度的增加而极显著降低,E型种子则与之相反。表明古尔班通古特沙漠未来随着降水的增加,B型、C型、D型种子的植物优势性逐渐增加,而E型种子的灌木类等物种优势性逐渐减少,注意加以保护。     

塔里木盆地南缘绿洲-沙漠过渡带8种植物C、N、P生态化学计量特征的季节变化

研究荒漠生态系统中乔木、灌木和草本叶片生态化学计量特征及其随季节变化的规律,旨在阐明不同生活型植物生长发育过程中生态化学计量特征动态平衡及其差异,为荒漠生态系统的保护与管理提供理论依据。选择塔里木盆地南缘绿洲-沙漠过渡带内不同生活型8种植物,在生长季的4—9月连续进行叶片采集,分析叶片C、N、P含量及其计量比在整个生长季的变化。结果表明：1)整体上,8种植物叶片C含量的季节变化不大,N、P含量在生长初期最高,之后逐步下降,体现了明显的稀释作用,而植物叶片的C∶N、C∶P和N∶P在整个生长季内的变化规律不一致;2)综合分析8种植物叶片C、N、P含量及其计量比值在整个生长季节内的变异,变异系数由大到小排序为：P (32.39%)>C∶P (25.67%)>N (20.96%)>N∶P (20.42%)>C∶N (19.83%)>C (6.49%);3)植物叶片C含量的变异主要受物种和生活型的影响,N、P含量及C∶N、C∶P的变异受物种和生长季的影响最大,而N∶P的变异受到生长季与物种的交互影响大于生长季的影响;4) 8种植物叶片N、P含量间存在极显著的正相关关系(P<0.001);P含量则与N∶P间呈现显著负相关(P<0.001),而N含量与N∶P间无显著相关性(P>0.05)。绿洲-沙漠过渡带8种植物叶片碳、氮、磷含量及其化学计量比在生长季因物种而不同,它们在生长季内的变异系数在物种间也存在差异,植物生长更容易受到N元素的限制。     

基于地形因素的新疆荒漠植被-气候模型应用研究

本研究在新疆荒漠植被型分类的基础上,用植被与气候Holdridge生命带模型进行荒漠植被型的模拟,并用Kappa检验系数进行结果检验,模拟结果很差(0.19),将地形作为模拟模型具体考虑的一个因素,对重新分类的气候区进行二次植被模拟。二次模拟结果Kappa检验系数平均值为0.45,二次模拟整体荒漠植被型模拟结果的Kappa检验系数为0.64,极大地提高了模型模拟的准确度。模型模拟准确度的提高在于将影响新疆水分分配的地形因素作为改进Holdridge生命带模型的参数,该参数的引入为提高Holdridge生命带模型的准确度提供了新的思路,也为较准确地模拟新疆地区的植被提供了新途径。