Anaerobic degradation of m-cresol by Desulfobacterium cetonicum is initiated by formation of 3-hydroxybenzylsuccinate

The anaerobic bacterium Desulfobacterium cetonicum oxidized m-cresol completely with sulfate as electron acceptor. During growth, 3-hydroxybenzylsuccinate (identified by gas chromatography/mass spectroscopy and by comparison of high-performance liquid chromatography retention time and UV spectrum with a chemically synthesized reference compound) accumulated in the medium. This finding indicates that the methyl group of m-cresol is activated by addition to fumarate as in the case of anaerobic toluene metabolism. In cell-free extracts of D. cetonicum, the formation of 3-hydroxybenzylsuccinate from m-cresol and fumarate was detected at an activity of 0.5 nmol min^–1 (mg protein)^–1. This reaction depended strictly on anoxic assay conditions. Treatment with air resulted in a complete loss of activity; however, some activity could be recovered after restoring anoxic conditions. The activity was slightly membrane-associated. 3-Hydroxybenzylsuccinate was degraded via CoA thioesterification and further oxidation to 3-hydroxybenzoyl-CoA as subsequent steps in the degradation pathway. Received: 20 May 1999 / Accepted: 19 July 1999     

西双版纳苦丁茶挥发油的化学成分

苦丁茶为中国南部及西南部的民间传统药用植物,经两千多年的应用和医学临床试验证明,苦丁茶具有清热解毒、抑菌消炎、抗衰老、降血脂、改善血液粘稠度和微循环、清除人体自由基及增强人体免疫能力等功效,被誉为保健茶、美容茶、降压茶和益寿茶[1,2]。苦丁茶来源较复杂,共有5科1     

锦鸡儿植物对盐碱地土壤理化性质和细菌群落的影响

锦鸡儿属的多种植物在干旱/半干旱区域水土保持等方面具有显著的作用效果,该研究以柠条锦鸡儿、中间锦鸡儿和小叶锦鸡儿为材料,选择宁夏银北西大滩核心试验站的盐渍化荒地为研究对象,分析了3种锦鸡儿建植1年对盐碱地土壤理化性质及土壤细菌群落的影响,以了解该类植物在盐碱地改良中的作用及生态效应。结果显示:(1)种植锦鸡儿1年能够显著降低盐碱地土壤全盐含量和pH,提高土壤全氮和全磷含量。(2)种植锦鸡儿不影响其非根际土壤细菌群落的α多样性,但小叶锦鸡儿非根际土壤细菌群落的香浓指数最低。(3)不同种锦鸡儿对盐碱地细菌群落结构的影响有所不同,小叶锦鸡儿根际/非根际细菌群落的结构分别与对照土壤以及柠条、中间锦鸡儿根际土壤存在明显差异;在属水平,包括假黄色单胞菌属、新鞘氨醇菌属及根瘤菌属在内的12个优势细菌属的相对丰度在小叶锦鸡儿非根际土壤中显著增加。(4)db-RDA分析表明,盐碱地土壤全盐、全氮及全磷含量分别解释了锦鸡儿非根际细菌群落结构变异信息的23.5%、25.4%和22.2%,3种因子累计共解释48.5%的细菌群落变异(P0.05),但这些因子对锦鸡儿根际细菌群落的变化无显著影响。研究表明,短期种植锦鸡儿属植物对盐碱地土壤理化性质具有一定改良效果,且不影响非根际土壤细菌群落的α多样性,但不同种锦鸡儿对土壤细菌群落结构的影响存在差异。     

Clinical Burkholderia pseudomallei isolates from north Queensland carry diverse bimABm genes that are associated with central nervous system disease and are phylogenomically distinct from other Australian strains

BackgroundBurkholderia pseudomallei is an environmental gram-negative bacterium that causes the disease melioidosis and is endemic in many countries of the Asia-Pacific region. In Australia, the mortality rate remains high at approximately 10%, despite curative antibiotic treatment being available. The bacterium is almost exclusively found in the endemic region, which spans the tropical Northern Territory and North Queensland, with clusters occasionally present in more temperate climates. Despite being endemic to North Queensland, these infections remain understudied compared to those of the Northern Territory.Methodology/Principal findingsThis study aimed to assess the prevalence of central nervous system (CNS) disease associated variant bimA_Bm, identify circulating antimicrobial resistance mutations and genetically distinct strains from Queensland, via comparative genomics. From 76 clinical isolates, we identified the bimA_Bm variant in 20 (26.3%) isolates and in 9 (45%) of the isolates with documented CNS infection (n = 18). Explorative analysis suggests a significant association between isolates carrying the bimA_Bm variant and CNS disease (OR 2.8, 95% CI 1.3–6.0, P = 0.009) compared with isolates carrying the wildtype bimA_Bp. Furthermore, 50% of isolates were identified as novel multi-locus sequence types, while the bimA_Bm variant was more commonly identified in isolates with novel sequence types, compared to those with previously described. Additionally, mutations associated with acquired antimicrobial resistance were only identified in 14.5% of all genomes.Conclusions/SignificanceThe findings of this research have provided clinically relevant genomic data of B. pseudomallei in Queensland and suggest that the bimA_Bm variant may enable risk stratification for the development CNS complications and be a potential therapeutic target.     

土壤增温与氮添加对杉木幼苗细根径级根长分布的影响

通过在福建省三明市陈大林业国有林场内开展土壤增温(增温5 ℃、不增温)和氮添加(不添加、4、8 g N·m^-2·a^-1)的交互试验(共6个处理),研究土壤增温、氮添加及二者交互作用对杉木细根径级根长分布的影响,用扩展模型可很好地拟合6个处理的径级根长分布(R²=0.97).结果表明: 增温使杉木细根总根长变小,但对细根直径影响不显著;氮添加使杉木细根总根长和直径均变小;增温和氮添加的交互作用对细根总根长有显著影响,但对细根直径无显著影响.6个处理细根径级根长分布均能用极值函数模型较好地拟合(R²>0.98).相关分析显示,直径<1 mm细根的比根长与极值模型拟合参数c值呈显著负相关,实际总根长与极值模型拟合参数b呈显著正相关.增温和氮添加及其交互作用可以影响杉木细根形态特征;极值模型拟合各处理径级根长分布所得参数在一定程度上可以反映细根形态特征对环境条件变化的响应.     

温光条件与寒地水稻产量和源库特征的关系

采用大田试验,以寒地水稻为研究对象,分析试验区2011—2014年气温和太阳辐射,比较不同年份间温光条件差异,探讨温光条件与水稻干物质积累、源库光合特征、产量及其构成之间的关系。结果表明:生育期内日活动积温利用率和日有效积温利用率呈逐年增加的趋势,而太阳辐射呈逐年降低的趋势,其中灌浆期太阳辐射强度以2014年居高;生育期内日活动积温和日有效积温及其利用率、抽穗后日平均太阳辐射强度与粒数、结实率、千粒重以及产量显著或极显著正相关;生育期内活动积温与产量(R~2=0.69)、生物产量(R~2=0.49)、抽穗期茎鞘干质量(R~2=0.74)及粒叶比(R~2=0.34)、收获指数(R~2=0.63)、群体生长速率(R~2=0.78)和净同化率(R~2=0.73)均呈二次函数关系,且拟合效果均达极显著水平,而与叶面积指数呈极显著正相关关系(R=0.80)。     

黄土高原不同植被覆盖对流域水文的影响

以山西省吉县蔡家川流域为对象,研究了植被覆盖类型对流域水文的影响.结果表明:不同植被覆盖的流域年径流系数分别为:林地流域1.6%～2.3%,以农、牧为主的流域3.1%～3.9%;各流域基流系数差异显著,人工林流域为零,次生林为主的流域1.0%～1.5%,以农、牧为主的流域2.5%～2.8%;在雨季人工林流域的径流总量是次生林流域的3.37倍、农地流域的1.9倍,而农地流域的基流量是次生林流域的2.2倍;短历时高强度降雨条件下,人工林流域、次生林流域地表径流量分别是农地流域的10.8倍和2.2倍;在历时较长的暴雨条件下,人工林流域单位面积上的洪峰流量是农地流域的3.4倍,次生林流域的6.9倍;在长历时、大雨量条件下,农地流域的径流量是次生林流域的1.8倍.水平梯田的水源涵养功能与次生林植被相当,次生林植被的水源涵养功能远好于人工植被,在水资源短缺的黄土高原应提倡植被的自然恢复.     

民族植物学：学科发展动态与展望

对民族植物学的学科发展进行了简要综述。民族植物学自1896年在美国诞生以来,经历了百年漫长的发展过程。民族植物学由早期的描述编目有用植物,已经发展到了实验性、技术性和定量性研究的新阶段;民族植物学的原理与方法已被广泛应用于植物资源的可持续利用、社区发展和生物多样性保护。近代民族植物学的学科发展可归纳为3个特征：(1)研究方法的进展主要表现在由记载编目和描述到实验性、技术性的定量研究和从基础研究到实际应用的发展;(2)研究途径的发展表现在由调查记录、访谈式的被动研究到参与式研究和取证分析;(3)研究地区已由局部区域性研究扩大到全球范围的民族植物学研究,从对原住民和少数民族的民族植物学研究扩展到所有不同文化背景民族的民族植物学研究。特别是发展中国家的民族植物学研究在近半个世纪以来得到迅速发展,并广泛应用于植物资源的管理和生物多样性保护的实际工作中。民族植物学在中国起步较晚,但在过去20年里已从无到有,建立起了我国民族植物学研究的理论框架、内容、方法和途径,将民族植物学从基础描述性研究(调查、记载、编目),推进到应用研究,在植物资源的可持续利用、生物多样性保护、农村发展和山区扶贫等方面取得了若干进展。当前,我国民族植物学研究面临着发展的新机遇和新的挑战,必须紧跟国民经济发展的新形势,投入西部大开发,加强学科建设,推进研究与产业发展的结合,把民族植物学由地区性研究推进到全国性研究,进一步完善中国特色的民族植物学研究体系,积极参与国际合作与交流,对国民经济的持续发展、民族地区的团结稳定和生物多样性保护作出更大的贡献。     

Reverse phase high performance liquid chromatography in the synthesis of leukotrienes A4 and C4

The chromatographic (RP HPLC) behaviour of leukotriene C4, its methyl ester, leukotriene A4 methyl ester and some chemicals involved in their synthesis have been investigated. Optimal conditions of separation were determined for the gradient and isocratic HPLC. Parameters of the interaction of the substances with hydrophobic surface are discussed in terms of solvophobic theory.     

特异腐质霉纤维素酶的研究

由腐植土中分离到一株嗜热真菌,经鉴定为特异腐质霉(Humicola insolens Cooney etEmerson)。研究了这株菌纤维素酶的产生条件和一般性质。菌在含麦麸5％、NaNO0.3％的液体培养基(灭菌前pH7.5,灭菌后pH7.2)中,于45℃培养4天,以羧甲基纤维素钠为底物,每ml滤液酶活力为20个单位。酶作用的最适条件为:pH6.0,温度为65—70℃。该纤维素酶是一种耐热酶,热稳定性较强,70℃保温5分钟后,酶活力剩余88％。底物对该酶的热钝化有较强的保护作用,无底物存在条件下,70℃保温6小时后,酶活力仅剩余1％,而在同样的处理温度和时间,在有底物存在条件下,酶活力可剩余30％。该酶在45℃保温15小时的条件下,pH稳定范围为6.0—9.0。