产氢新菌Ethanoligenens sp. B49发酵糖蜜制氢条件

研究1株产氢细菌Ethanoligenens sp.B49利用废糖蜜为基本原料进行生物制氢的条件,及外加氮素营养物对废糖蜜生物制氢的影响.结果表明,在10.3～20.6 g·L-1的化学需氧量(COD)范围内,经过驯化的Ethanoligenens sp.B49细胞具有较好的生物利用能力,细胞生长量和产氢能力随着废糖蜜COD的提高而增加.当废糖蜜COD超过20.6 g·L-1时Ethanoligenens sp.B49的细胞生长受到抑制,同时产氢能力下降,COD超过41.2 g·L-1时细胞基本不具有生长和产氢能力.Ethanoligenens sp.B49利用废糖蜜产氢的最佳COD为20.6 g·L-1.在20.6 g·L-1COD条件下外加有机氮源可以促进Ethanoligenens sp.B49利用废糖蜜制氢的能力,促进作用顺序为酵母粉＞牛肉膏＞蛋白胨＞脲素.添加4 g·L-1的酵母粉时,Ethanoligenens sp.B49细胞具有最好的生长活性和产氢能力.优化营养条件后,单位体积产氢量从44.82 mmol·L-1提高到78.97 mmol·L-1,提高了76.2%.     

Selection for novel metabolic capabilities in Salmonella enterica

Bacteria are known to display extensive metabolic diversity and many studies have shown that they can use an extensive repertoire of small molecules as carbon‐ and energy sources. However, it is less clear to what extent a bacterium can expand its existing metabolic capabilities by acquiring mutations that, for example, rewire its metabolic pathways. To investigate this capability and potential for evolution of novel phenotypes, we sampled large populations of mutagenized Salmonella enterica to select very rare mutants that can grow on minimal media containing 124 low molecular weight compounds as sole carbon sources. We found mutants growing on 18 of these novel carbon sources, and identified the causal mutations that allowed growth for four of them. Mutations that relieve physiological constraints or increase expression of existing pathways were found to be important contributors to the novel phenotypes. For the remaining 14 novel phenotypes, whole genome sequencing of independent mutants and genetic analysis suggested that these novel metabolic phenotypes result from a combination of multiple mutations. This work, by virtue of identifying the genetic and mechanistic basis for new metabolic capabilities, sheds light on the properties of adaptive landscapes underlying the evolution of novel phenotypes.     

二氢乳清酸脱氢酶的结构特征和催化循环研究进展

二氢乳清酸脱氢酶是黄素依赖的线粒体酶,它催化嘧啶从头合成的第4步反应,将二氢乳清酸氧化为乳清酸。通过选择性抑制二氢乳清酸脱氢酶,从而抑制嘧啶的合成,已被开发用于治疗癌症、自身免疫性疾病、细菌或病毒感染以及寄生虫疾病等。抑制剂的开发需详细了解二氢乳清酸脱氢酶的结构特征和催化循环机制。因此,文中主要从这两个方面进行了综述,并展望了该酶的抑制剂在临床应用中的前景。     

Cretaceous origins of the vibrotactile bill-tip organ in birds

Some probe-foraging birds locate their buried prey by detecting mechanical vibrations in the substrate using a specialized tactile bill-tip organ comprising mechanoreceptors embedded in densely clustered pits in the bone at the tip of their beak. This remarkable sensory modality is known as ‘remote touch’, and the associated bill-tip organ is found in probe-foraging taxa belonging to both the palaeognathous (in kiwi) and neognathous (in ibises and shorebirds) clades of modern birds. Intriguingly, a structurally similar bill-tip organ is also present in the beaks of extant, non-probing palaeognathous birds (e.g. emu and ostriches) that do not use remote touch. By comparison with our comprehensive sample representing all orders of extant modern birds (Neornithes), we provide evidence that the lithornithids (the most basal known palaeognathous birds which evolved in the Cretaceous period) had the ability to use remote touch. This finding suggests that the occurrence of the vestigial bony bill-tip organ in all modern non-probing palaeognathous birds represents a plesiomorphic condition. Furthermore, our results show that remote-touch probe foraging evolved very early among the Neornithes and it may even have predated the palaeognathous–neognathous divergence. We postulate that the tactile bony bill-tip organ in Neornithes may have originated from other snout tactile specializations of their non-avian theropod ancestors.     

A Na+/H+ antiporter gene of the moderately halophilic bacterium Halobacillus dabanensis D-8T: cloning and molecular characterization

A gene encoding a Na(+)/H(+) antiporter was cloned from a chromosomal DNA of Halobacillus dabanensis strain D-8(T) by functional complementation. Its presence enabled the antiporter-deficient Escherichia coli strain KNabc to survive in the presence of 0.2 M NaCl or 5 mM LiCl. The gene was sequenced and designated as nhaH. The deduced amino-acid sequence of NhaH consists of 403 residues with a calculated molecular mass of 43,481 Da, which was 54% identical and 76% similar to the NhaG Na(+)/H(+) antiporter of Bacillus subtilis. The hydropathy profile was characteristic of a membrane protein with 12 putative transmembrane domains. Everted membrane vesicles prepared from E. coli cells carrying nhaH exhibited Na(+)/H(+) as well as Li(+)/H(+) antiporter activity, which was pH-dependent with highest activities at pH 8.5-9.0 and at pH 8.5, respectively. Moreover, nhaH confers upon E. coli KNabc cells the ability to grow under alkaline conditions.     

阔叶红松林合理经营与土壤微生物活性

森林是可再生的自然资源,研究证明,阔叶红松林具有很高的生产力,因为它具有最优化的林分结构,这个结构特点,使它的复层异龄和针阔混交的群落结构影响下的土壤肥力较高,土壤微生物类群复杂,活动活跃,森林有机残体的分解与转化较快。系统内的氮、碳及无机养分的循环,能满足林木生长对养分不断增长的需要。系统内各个生态因子处于动态平衡状态。因此,为了不断提     

施肥对旱地花生主要土壤肥力指标及产量的影响

大田条件下,研究了纯无机肥及不同用量有机-无机配施对旱地砂壤土花生土壤微生物种群及数量、土壤主要酶活性、土壤呼吸速率及产量的影响,结果表明:(1)土壤中细菌、放线菌和真菌数量随有机无机肥配施数量的增加而增加;单施无机复合肥对微生物数量的增加不明显,中量有机无机肥配施比单纯施中量无机肥处理的细菌、放线菌和真菌数量全生育期平均值分别提高114.9％、49.0％和29.0％.(2)施肥可以显著提高土壤脲酶、蔗糖酶、酸性磷酸酶、过氧化氢酶活性及土壤呼吸速率,其中有机无机中、高量配施显著高于其他处理,中量纯无机肥(农民常规施肥)相近于或低于(尤其在生育后期)低量有机无机肥配施;施肥对土壤过氧化氢酶活性的影响小于其余3种酶.(3)不同类群土壤微生物数量、土壤主要酶活性及土壤呼吸作用关系密切,相互间相关系数均达到极显著水平.(4)有机无机中、高量配施花生产量显著高于其他处理,中量无机肥加中量有机肥比中量纯无机肥增产14.0％,表明在砂壤土上施用有机肥,其对土壤肥力提高的增产作用远远大于其本身所含花生生育所需营养直接供应作用.(5)兼顾土壤肥力和花生产量,肥力中等的砂壤土,可采用中量有机无机肥混配施用.     

Turquoise is the new green: Restoring and enhancing riparian function in the Anthropocene

Riparian ecosystems are hotspots for ecological restoration globally because of the disproportionately high value and diversity of the ecological functions and services which they support and their high level of vulnerability to anthropogenic pressures, including climate change. Degraded riparian ecosystems are associated with many serious anthropogenic problems including increased river bank erosion, water quality decline, increased flood risk and biodiversity loss. Conventional approaches to riparian restoration, however, are frequently too narrow in focus – spatially, temporally, ecologically and socially – to adequately or equitably address the goals to which they aspire. Climate change, along with the intensification of other human pressures, means that static, historically oriented restoration objectives focused solely on prior ecological composition and structure are unlikely to be defensible, achievable or appropriate in the Anthropocene. Conversely, open‐ended restoration strategies lacking clear objectives and targets entail substantial risks such as significant biodiversity losses, especially of native species. A functional approach to planning and prioritising riparian restoration interventions offers an intermediate alternative that is still framed by measurable targets but allows for greater consideration of broader temporal, spatial and cultural influences. Here, we provide an overview of major riparian functions across multiple scales and identify key drivers of, and threats to, these. We also discuss practical approaches to restoring and promoting riparian functions and highlight some key concerns for the development of policy and management of robust riparian restoration in the Anthropocene.