小兴安岭大亮子河国家森林公园不同生境下土壤细菌多样性和群落结构

土壤细菌是森林生态系统的一个重要组成成分, 是生态系统中物质循环和能量流动的重要参与者, 细菌群落组成和生物多样性是反映土壤生态功能的重要指标。本文利用高通量测序技术分析了大亮子河国家森林公园内红松(Pinus koraiensis)林、落叶松(Larix gmelinii)林、蒙古栎(Quercus mongolica)林、枫桦(Betula costata)林、针阔混交林、灌木林和草甸等7种不同生境土壤细菌群落组成和多样性的差异性, 探讨该地区土壤细菌群落对不同生境的响应, 为地区森林生态系统的经营管理及生态系统稳定性的维护提供科学理论基础。在门的水平上, 各生境的细菌群落组成基本一致, 其中变形菌门(Proteobacteria)、放线菌门(Actinobacteria)、酸杆菌门(Acidobacteria)和疣微菌门(Verrucomicrobia)在7种生境土壤中相对丰度均大于10.0%, 是细菌中的优势菌门。在属的水平上, 共测得245个菌属, 各样地共有属118个, 占总属数的48.2%, 占总相对丰度的97.8%; 优势菌属分别为Spartobacteria_ genera_incertae_sedis、Gaiella、Gp16、Gp4, 占总相对丰度的47.0%, Spartobacteria_genera_incertae_sedis在7种生境土壤中丰度均最高。7种生境下的土壤细菌多样性和土壤理化因子存在着显著的差异, 红松林的土壤细菌群落多样性和丰富度均高于其他生境。土壤pH是大亮子河森林公园影响土壤细菌多样性的关键因子。     

Hydrogen and oxygen trapping at the H-cluster of [FeFe]-hydrogenase revealed by site-selective spectroscopy and QM/MM calculations

[FeFe]-hydrogenases are superior hydrogen conversion catalysts. They bind a cofactor (H-cluster) comprising a four-iron and a diiron unit with three carbon monoxide (CO) and two cyanide (CN^?) ligands. Hydrogen (H₂) and oxygen (O₂) binding at the H-cluster was studied in the C169A variant of [FeFe]-hydrogenase HYDA1, in comparison to the active oxidized (Hox) and CO-inhibited (Hox-CO) species in wildtype enzyme. ⁵⁷Fe labeling of the diiron site was achieved by in vitro maturation with a synthetic cofactor analogue. Site-selective X-ray absorption, emission, and nuclear inelastic/forward scattering methods and infrared spectroscopy were combined with quantum chemical calculations to determine the molecular and electronic structure and vibrational dynamics of detected cofactor species. Hox reveals an apical vacancy at Fe_d in a [4Fe4S-2Fe]^3 ? complex with the net spin on Fe_d whereas Hox-CO shows an apical CN^? at Fe_d in a [4Fe4S-2Fe(CO)]^3 ? complex with net spin sharing among Fe_p and Fe_d (proximal or distal iron ions in [2Fe]). At ambient O₂ pressure, a novel H-cluster species (Hox-O₂) accumulated in C169A, assigned to a [4Fe4S-2Fe(O₂)]^3 ? complex with an apical superoxide (O₂^?) carrying the net spin bound at Fe_d. H₂ exposure populated the two-electron reduced Hhyd species in C169A, assigned as a [(H)4Fe4S-2Fe(H)]^3 ? complex with the net spin on the reduced cubane, an apical hydride at Fe_d, and a proton at a cysteine ligand. Hox-O₂ and Hhyd are stabilized by impaired O₂^– protonation or proton release after H₂ cleavage due to interruption of the proton path towards and out of the active site.     

Synthesis and profiling of benzylmorpholine 1,2,4,5-tetraoxane analogue N205: Towards tetraoxane scaffolds with potential for single dose cure of malaria

A series of aryl carboxamide and benzylamino dispiro 1,2,4,5-tetraoxane analogues have been designed and synthesized in a short synthetic sequence from readily available starting materials. From this series of endoperoxides, molecules with in vitro IC50s versus Plasmodium falciparum (3D7) as low as 0.84?nM were identified. Based on an assessment of blood stability and in vitro microsomal stability, N205 (10a) was selected for rodent pharmacokinetic and in vivo antimalarial efficacy studies in the mouse Plasmodium berghei and Plasmodium falciparum Pf3D70087/N9 severe combined immunodeficiency (SCID) mouse models. The results indicate that the 4-benzylamino derivatives have excellent profiles with a representative of this series, N205, an excellent starting point for further lead optimization studies.     

黄土高原水土流失治理现状、问题及对策

黄土高原位于黄河中游地区,是世界上水土流失最为严重的区域之一;黄土高原水土流失治理问题历来受到国家高度关注,涌现了种类多样的水土流失治理模式,目前还缺乏对黄土高原区域尺度水土流失治理模式的总结和整理。本文总结和整理了建国以来黄土高原主要的四类水土流失治理模式,生物措施模式主要由退耕还林、荒山造林和封山育林工程组成,工程措施模式包括修建梯田和淤地坝,以及近期涌现的治沟造地工程;小流域综合治理模式主要体现在坡面、沟道系统整治,生物和工程措施相结合的特点,区域综合整理模式则强调对生态系统进行整体保护、系统修复和综合治理,达到生态、社会、经济可持续发展。基于黄土高原水土流失治理模式存在的问题,提出了黄土高原水土流失治理模式调整和优化建议,以期对黄土高原生态恢复建设和水土流失科学治理提供科学依据。     

The emerging role and targetability of the TCA cycle in cancer metabolism

The tricarboxylic acid (TCA) cycle is a central route for oxidative phosphorylation in cells, and fulfills their bioenergetic, biosynthetic, and redox balance requirements. Despite early dogma that cancer cells bypass the TCA cycle and primarily utilize aerobic glycolysis, emerging evidence demonstrates that certain cancer cells, especially those with deregulated oncogene and tumor suppressor expression, rely heavily on the TCA cycle for energy production and macromolecule synthesis. As the field progresses, the importance of aberrant TCA cycle function in tumorigenesis and the potentials of applying small molecule inhibitors to perturb the enhanced cycle function for cancer treatment start to evolve. In this review, we summarize current knowledge about the fuels feeding the cycle, effects of oncogenes and tumor suppressors on fuel and cycle usage, common genetic alterations and deregulation of cycle enzymes, and potential therapeutic opportunities for targeting the TCA cycle in cancer cells. With the application of advanced technology and in vivo model organism studies, it is our hope that studies of this previously overlooked biochemical hub will provide fresh insights into cancer metabolism and tumorigenesis, subsequently revealing vulnerabilities for therapeutic interventions in various cancer types.     

Genotyping strategy matters when analyzing hypervariable major histocompatibility complex‐Experience from a passerine bird

Genotyping of classical major histocompatibility complex (MHC) genes is challenging when they are hypervariable and occur in multiple copies. In this study, we used several different approaches to genotype the moderately variable MHC class I exon 3 (MHCIe3) and the highly polymorphic MHC class II exon 2 (MHCIIβe2) in the bluethroat (Luscinia svecica). Two family groups (eight individuals) were sequenced in replicates at both markers using Ion Torrent technology with both a single‐ and a dual‐indexed primer structure. Additionally, MHCIIβe2 was sequenced on Illumina MiSeq. Allele calling was conducted by modifications of the pipeline developed by Sommer et al. (BMC Genomics, 14, 2013, 542) and the software AmpliSAS. While the different genotyping strategies gave largely consistent results for MHCIe3, with a maximum of eight alleles per individual, MHCIIβe2 was remarkably complex with a maximum of 56 MHCIIβe2 alleles called for one individual. Each genotyping strategy detected on average 50%–82% of all MHCIIβe2 alleles per individual, but dropouts were largely allele‐specific and consistent within families for each strategy. The discrepancies among approaches indicate PCR biases caused by the platform‐specific primer tails. Further, AmpliSAS called fewer alleles than the modified Sommer pipeline. Our results demonstrate that allelic dropout is a significant problem when genotyping the hypervariable MHCIIβe2. As these genotyping errors are largely nonrandom and method‐specific, we caution against comparing genotypes across different genotyping strategies. Nevertheless, we conclude that high‐throughput approaches provide a major advance in the challenging task of genotyping hypervariable MHC loci, even though they may not reveal the complete allelic repertoire.     

Predicted structures of two proteins involved in human diseases

Structures of 79 proteins involved in human diseases were predicted by sequence alignments with structural templates. The predicted structures for ALDP and CSA, proteins responsible for adrenoleukodystrophy and the Cockayne syndrome, respectively, were analyzed to elucidate the molecular basis of disease mutations. In particular we positioned residue P484 of ALDP in the homodimer interface. This positioning is consistent with a recent experimental finding that the mutation P484R significantly decreases the self-interaction of ALDP and suggests that the disease mechanism of this mutation lies in the impaired ALDP dimerization. We identified two new WD repeats in CSA and suggest that one of these forms part of the interaction surface with other proteins.     

Cyanobacterial–Bacterial Complexes in Plant Syncyanoses

The morphology and ultrastructure of associative microsymbiont complexes (AMC) isolated from the ferns Azolla pinnata and Azolla sp. and the apogeotropic roots of the cycad Cycas revoluta were studied. The composition of the AMC obtained includes the cyanobionts (symbiotic cyanobacteria) and satellite bacteria (SB). It was found that two types of cyanobacteria that substantially differ in their morphological organization are likely present as cyanobionts in the coralloids of C. revoluta. The isolated cyanobiont strains exhibited the morphological traits and regularities of development typical of the genus Nostoc; they were characterized by the ability of their cells to divide in mutually perpendicular planes. When isolating AMC from different morphological zones of C. revoluta apogeotropic roots, SB growth was revealed only around the pieces corresponding to the coralloid apical zone. No AMC components were revealed around the segments of the basal growth zone. Pure cyanobiont cultures were obtained from the AMC of C. revoluta coralloids. The AMC isolated from the ferns A. pinnata and Azolla sp. are characterized by obligate mutual dependence of the partners (the cyanobiont and SB).