间甲酚及施磷对小麦间作蚕豆土壤微生物和酶活性的影响

通过盆栽试验,研究了不同磷水平下化感物质间甲酚对小麦间作蚕豆和单作小麦、单作蚕豆土壤微生物和酶活性的影响。结果表明,间甲酚对不同模式生长盛期细菌和微生物总数表现为化感促进作用,对真菌表现为化感抑制作用,随施磷量的增加间甲酚对土壤微生物的化感促进作用降低;不同模式生长盛期土壤微生物数量在施磷量为100mg／kg土的处理中最高,但成熟期施磷量为200mg／kg土的处理最高;间作较单作具有保持较高土壤细菌和微生物总数的作用,施磷水平越高间作增大微生物数量的效果越大;间甲酚对土壤微生物多样性具有明显降低作用,间作土壤的微生物多样性低于单作。间作具有较高的弱化间甲酚对土壤过氧化氢酶化感负效应的作用,施磷可增强土壤过氧化氢酶活性;磷素作用下土壤脲酶活性增强,间甲酚对单作蚕豆和间作土壤脲酶活性具有促进作用,但弱化了施磷对脲酶活性的增强作用;增施磷肥可弱化间甲酚对单作蚕豆和间作土壤酸性磷酸酶的化感负效应,对单作小麦土壤酸性磷酸酶活性的影响相反。间甲酚对不同模式土壤微生物和酶活性的影响在作物成熟期显著下降,说明随时间的推移土壤中间甲酚的作用力在不断弱化。     

Emerging roles of low-molecular-weight thiols at the host–microbe interface

Low-molecular-weight (LMW) thiols are an abundant class of cysteine-derived small molecules found in all forms of life that maintain reducing conditions within cells. While their contributions to cellular redox homeostasis are well established, LMW thiols can also mediate other aspects of cellular physiology, including intercellular interactions between microbial and host cells. Here we discuss emerging roles for these redox-active metabolites at the host–microbe interface. We begin by providing an overview of chemical and computational approaches to LMW-thiol discovery. Next, we highlight mechanisms of virulence regulation by LMW thiols in infected cells. Finally, we describe how microbial metabolism of these compounds may influence host physiology.     

Sources,fates, and impacts of nitrogen inputs to terrestrial ecosystems: review and synthesis

The relative importance of nitrogen inputs from atmospheric deposition and biological fixation is reviewed in a number of diverse, non-agricultural terrestrial ecosystems. Bulk precipitation inputs of N (l–l2 kg N ha^–1 yr^–1) are the same order of magnitude as, or frequently larger than, the usual range of inputs from nonsymbiotic fixation (< 1=" –=" 5=" kg=" n=">^–1 yr^–1), especially in areas influenced by industrial activity. Bulk precipitation measurements may underestimate total atmospheric deposition by 30–40% because they generally do not include all forms of wet and dry deposition. Symbiotic fixation generally ranges from 10–160 kg N ha^–1 yr^–1) in ecosystems where N-fixing species are present during early successional stages, and may exceed the range under unusual conditions.Rates of both symbiotic and nonsymbiotic fixation appear to be greater during early successional stages of forest development, where they have major impacts on nitrogen dynamics and ecosystem productivity. Fates and impacts of these nitrogen inputs are important considerations that are inadequately understood. These input processes are highly variable in space and time, and few sites have adequate comparative information on both nitrogen deposition and fixation.

玉米 线辣椒套作系统中土壤养分与根际土壤微生物、酶活性的关系

采用玉米单作、线辣椒单作、玉米-线辣椒套作3种栽培模式,并在玉米-线辣椒套作的种间根部设3种不同隔离处理（膜隔、网隔和无隔）,研究了玉米-线辣椒套作系统中土壤生物因子与土壤养分的关系．结果表明：玉米-线辣椒套作具有明显优势;与两作物单作和玉米-线辣椒套作种间根区膜隔处理相比,玉米-线辣椒根区无隔和网隔处理复合群体中两作物根际土壤酶活性、微生物数量、土壤养分均显著提高;除有效镁与真菌种群数量、过氧化氢酶活性呈负相关外,其余速效养分与各生物因子均呈显著或极显著正相关．通径分析表明,该系统中促进有机质累积的主要生物因素是脲酶、过氧化氢酶、细菌和蛋白酶,蔗糖酶是影响碱解氮的最主要因子,脲酶是影响有效磷的最主要因子,细菌是影响有效钾的最主要因子,碱性磷酸酶、真菌只是选择性地对有机质的累积和氮、磷、钾有效养分的形成起作用,放线菌对土壤养分的直接作用系数为负,对土壤养分形成的作用较小．     

An automated screening method for drugs and toxic compounds in human serum and urine using liquid chromatography–tandem mass spectrometry

A fully automated screening using liquid chromatography–mass spectrometric method applying data-dependent acquisition was developed to identify toxicologically relevant substances in serum and urine. A library including more than 405 spectra of about 365 compounds (main drugs and important metabolites) was established. An easy to use program was created to automate and accelerate library search. Drugs were identified based on their relative retention times, molecular ions and fragment ions. Limits of detection were tested with 100 of the 365 compounds the majority of these were lower than 100 μg/l (67%). The developed LC–MS–MS system seems to be a valuable alternative to other general unknown screening methods allowing fast and specific identification of drugs in serum and urine samples.     

骆驼瘤胃耐受/降解去氢骆驼蓬碱细菌的筛选

【目的】中药骆驼蓬含多种生物碱,对动物有毒性。生活于荒漠半荒漠的骆驼可采食部分有毒植物而不中毒。为了解骆驼瘤胃微生物对骆驼蓬植物毒素的耐受与降解能力进行本研究。【方法】以含100mg/L纯品去氢骆驼蓬碱的M98-5培养基接种骆驼瘤胃内容物,经五代胁迫培养后分离可耐受/降解去氢骆驼蓬碱的细菌,以薄层析法检验其降解活力,以16SrRNA序列分析其进化地位。【结果】29个分离株中15株具有降解去氢骆驼蓬碱活性;16SrRNA序列分析显示,属于乳杆菌属(Lactobacillus)16株,占55%;志贺氏菌属(Shigella)7株,占24%;芽孢杆菌属(Bacillus)4株,占13.8%;肠球菌属(Enterococcus)和巨型肠球菌属(Megasphaera)各1株。【结论】可耐受/降解去氢骆驼蓬碱的骆驼瘤胃细菌仅限于少数几类,且检测到的具有降解活力的只有乳杆菌类。     

Global change‐driven effects on dissolved organic matter composition: Implications for food webs of northern lakes

Northern ecosystems are experiencing some of the most dramatic impacts of global change on Earth. Rising temperatures, hydrological intensification, changes in atmospheric acid deposition and associated acidification recovery, and changes in vegetative cover are resulting in fundamental changes in terrestrial–aquatic biogeochemical linkages. The effects of global change are readily observed in alterations in the supply of dissolved organic matter (DOM)—the messenger between terrestrial and lake ecosystems—with potentially profound effects on the structure and function of lakes. Northern terrestrial ecosystems contain substantial stores of organic matter and filter or funnel DOM, affecting the timing and magnitude of DOM delivery to surface waters. This terrestrial DOM is processed in streams, rivers, and lakes, ultimately shifting its composition, stoichiometry, and bioavailability. Here, we explore the potential consequences of these global change‐driven effects for lake food webs at northern latitudes. Notably, we provide evidence that increased allochthonous DOM supply to lakes is overwhelming increased autochthonous DOM supply that potentially results from earlier ice‐out and a longer growing season. Furthermore, we assess the potential implications of this shift for the nutritional quality of autotrophs in terms of their stoichiometry, fatty acid composition, toxin production, and methylmercury concentration, and therefore, contaminant transfer through the food web. We conclude that global change in northern regions leads not only to reduced primary productivity but also to nutritionally poorer lake food webs, with discernible consequences for the trophic web to fish and humans.     

Enhanced regional terrestrial carbon uptake over Korea revealed by atmospheric CO2 measurements from 1999 to 2017

Understanding changes in terrestrial carbon balance is important to improve our knowledge of the regional carbon cycle and climate change. However, evaluating regional changes in the terrestrial carbon balance is challenging due to the lack of surface flux measurements. This study reveals that the terrestrial carbon uptake over the Republic of Korea has been enhanced from 1999 to 2017 by analyzing long‐term atmospheric CO₂ concentration measurements at the Anmyeondo Station (36.53°N, 126.32°E) located in the western coast. The influence of terrestrial carbon flux on atmospheric CO₂ concentrations (ΔCO₂) is estimated from the difference of CO₂ concentrations that were influenced by the land sector (through easterly winds) and the Yellow Sea sector (through westerly winds). We find a significant trend in ΔCO₂ of ?4.75 ppm per decade (p < .05) during the vegetation growing season (May through October), suggesting that the regional terrestrial carbon uptake has increased relative to the surrounding ocean areas. Combined analysis with satellite measured normalized difference vegetation index and gross primary production shows that the enhanced carbon uptake is associated with significant nationwide increases in vegetation and its production. Process‐based terrestrial model and inverse model simulations estimate that regional terrestrial carbon uptake increases by up to 18.9 and 8.0 Tg C for the study period, accounting for 13.4% and 5.7% of the average annual domestic carbon emissions, respectively. Atmospheric chemical transport model simulations indicate that the enhanced terrestrial carbon sink is the primary reason for the observed ΔCO₂ trend rather than anthropogenic emissions and atmospheric circulation changes. Our results highlight the fact that atmospheric CO₂ measurements could open up the possibility of detecting regional changes in the terrestrial carbon cycle even where anthropogenic emissions are not negligible.     

High‐altitude adaptation in vertebrates as revealed by mitochondrial genome analyses

The high‐altitude environment may drive vertebrate evolution in a certain way, and vertebrates living in different altitude environments might have different energy requirements. We hypothesized that the high‐altitude environment might impose different influences on vertebrate mitochondrial genomes (mtDNA). We used selection pressure analyses and PIC (phylogenetic independent contrasts) analysis to detect the evolutionary rate of vertebrate mtDNA protein‐coding genes (PCGs) from different altitudes. The results showed that the ratio of nonsynonymous/synonymous substitutions (dN/dS) in the mtDNA PCGs was significantly higher in high‐altitude vertebrates than in low‐altitude vertebrates. The seven rapidly evolving genes were shared by the high‐altitude vertebrates, and only one positive selection gene (ND5 gene) was detected in the high‐altitude vertebrates. Our results suggest the mtDNA evolutionary rate in high‐altitude vertebrates was higher than in low‐altitude vertebrates as their evolution requires more energy in a high‐altitude environment. Our study demonstrates the high‐altitude environment (low atmospheric O₂ levels) drives vertebrate evolution in mtDNA PCGs.