Engineering surface hydrophobicity improves activity of Bacillus thermocatenulatus lipase 2 enzyme

Bacillus thermocatenulatus lipase 2 (BTL2) is a promising industrial enzyme used in biodiesel production. Although BTL2 has high thermostability and good resistance to organic solvents, the activity of BTL2 is suboptimal for industrial processes. To improve BTL2 activity, we engineered BTL2 lipase by modulating hydrophobicity of its lid domain. Through site‐directed mutagenesis, we constructed three mutants, namely Y225F+S232A, S232A+T236V and Q185L, to cover all uncharged hydrophilic amino acids within the lid domain. Activities of these mutants were characterized. Our findings suggest that one mutant (Y225F+S232A) showed ～35% activity increase in catalyzing heterogeneous hydrolytic reactions relevant for industrial applications. A mathematical framework was established to account for different molecular events that contribute to the observed apparent catalytic activities. Increases in hydrophobicity of lid domains were associated with increased interfacial adsorption of lipases and lower molecular enzymatic activities. The measured apparent activities of lipases include contributions from both events. Lid hydrophobicity can thus result in different changes in lipase activities depending on the mutation site. Our work demonstrates the feasibility of increasing BTL2 activity by modulating the hydrophobicity of lid domains and provides some guidelines for further improving BTL2 activity.     

Distribution and diversity of palms in a tropical biodiversity hotspot (Thailand) assessed by species distribution modeling

Species distribution modeling has been widely used to address questions related to ecology, biogeography and species conservation on global and regional scales. Here, we study palms (Arecaceae) in a tropical biodiversity hotspot (Thailand) using species distribution modeling to assess range‐limiting factors and estimate distribution and diversity patterns based on a comprehensive compilation of occurrence records. We focused on palms as a model group due to their key‐stone importance for ecosystem functioning and socio‐economics. Different combinations of climatic, non‐climatic environmental and spatial predictors were used. The most accurate models as indicated by the ‘area under the receiver operating characteristic curve’ (AUC) statistic were those that combined all predictors. The four strongest single predictors of palm species distributions were, in decreasing order of importance, 1) latitude, 2) precipitation of driest quarter, 3) annual precipitation, and 4) minimum temperature of the coldest month, suggesting rainfall patterns and latitudinal spatial constraints as the main range determinants. Overlaying the predicted distributions revealed that potential palm hotspots are situated in the provinces of Satun and Yala in southern Thailand where vast areas remain relatively open to the discovery of new palm records and perhaps even new species.     

源自大黄鱼肠道柠檬酸杆菌的外切几丁质酶的特性分析（英文）北大核心CSCD

【目的】从饲喂富含几丁质饲料的大黄鱼肠道分离具有几丁质分解功能的菌株并分离鉴定新的几丁质酶。【方法】利用胶体几丁质平板分离饲喂杂鱼的大黄鱼肠道中的几丁质分解菌。对几丁质酶基因chi-X进行了克隆并在大肠杆菌中表达。对CHI-X的酶学性质进行了分析。【结果】从饲喂杂鱼的大黄鱼肠道内容物中分离出1株具有几丁质分解功能的费氏柠檬酸杆菌,其中的几丁质酶基因编码1个含493个氨基酸残基的蛋白,其中包含一个糖苷水解酶18家族催化域。CHI-X对胶体几丁质具有分解功能。最适p H和温度分别是4.0和60°C。CHI-X具有很强的pH稳定性,在pH 3.0–11.0的范围培育1 h仍保留90%左右的活性。Mn^(2+),Li^+和K^+可促进CHI-X酶活,Ag^+对CHI-X有抑制作用。CHI-X对蛋白酶和石斑鱼肠道内容物有较强的抗逆性。CHI-X可分解胶体几丁质为N-乙酰葡萄糖胺和N-乙酰葡萄糖胺二聚体,表明它是一个几丁质外切酶。最后,CHI-X和另一个几丁质酶Chi565表现出酶活性的加和效应。【结论】分离自肠道菌的CHI-X能很好适应海水鱼类的肠道环境,可以作为温水海水养殖鱼类的饲料添加剂使用。     

Salinity Impact on Bacterial Community Composition in Five High-Altitude Lakes from the Tibetan Plateau,Western China

The influence of salinity and geographical distance on bacterial community composition (BCC) in five freshwater, oligosaline or polysaline lakes located at altitudes higher than 4400 m on the central and southern Tibetan Plateau were investigated using the 16S rRNA gene clone library approach together with multivariate analysis of environmental variables. A total of 10 clone libraries were constructed with two libraries in each lake, one in the epilimnion and the other in the hypolimnion. Geographical distance was not found to impact BCC significantly, but salinity, chl a and lake hydraulic retention time were significant factors influencing the BCC. Bacteria in lakes located on the central and southern Plateau owned the same community composition as that observed from the eastern Tibetan lakes. They were both predominated by Bacteroidetes and Cyanobacteria, had low taxon richness, and similar typical freshwater clusters and distributed characteristics. Supplemental materials are available for this article. Go to the publisher's online edition of Geomicrobiology Journal to view the supplemental file.     

Intentionally introduced species: more easily invited than removed

Alien species are brought into countries world wide on a massive scale for agricultural production, ex situ conservation, landscape aesthetics, gardens, and ecosystem restoration. Unfortunately, some of these species have escaped and adversely impacted on regional as well as global biodiversity conservation and agricultural production. To reduce such risks, it is necessary to implement specific and effective measures. Since various government departments and institutions are involved in the management of alien species, it is difficult to prevent native and agroecosystems from being invaded by invited species. We propose the establishment of a supervision and inspection continuum over intentional species introduction, similar to that which exists in some countries over unintentional species introductions. Namely, a justification of the necessity to import, a risk assessment, assurances as to provision of an adequate containment facility assessment, and a damage-limitation protocol should that need to be invoked. These requirements should be satisfied before an alien species is knowingly imported, and the necessary follow-up supervision is important post- importation.     

Modeling interaction between gp120 HIV protein and CCR5 receptor

The study of the process of HIV entry into the host cell and the creation of biomimetic nanosystems that are able to selectively bind viral particles and proteins is a high priority research area for the development of novel diagnostic tools and treatment of HIV infection. Recently, we described multilayer nanoparticles (nanotraps) with heparin surface and cationic peptides comprising the N‐terminal tail (Nt) and the second extracellular loop (ECL2) of CCR5 receptor, which could bind with high affinity some inflammatory chemokines, in particular, Rantes. Because of the similarity of the binding determinants in CCR5 structure, both for chemokines and gp120 HIV protein, here we expand this approach to the study of the interactions of these biomimetic nanosystems and their components with the peptide representing the V3 loop of the activated form of gp120. According to surface plasmon resonance results, a conformational rearrangement is involved in the process of V3 and CCR5 fragments binding. As in the case of Rantes, ECL2 peptide showed much higher affinity to V3 peptide than Nt (K_D = 3.72 × 10^?8 and 1.10 × 10^?6 M, respectively). Heparin‐covered nanoparticles bearing CCR5 peptides effectively bound V3 as well. The presence of both heparin and the peptides in the structure of the nanotraps was shown to be crucial for the interaction with the V3 loop. Thus, short cationic peptides ECL2 and Nt proved to be excellent candidates for the design of CCR5 receptor mimetics.     

The pulse of the tree is under genetic control: eucalyptus as a case study

The pulse of the tree (diurnal cycle of stem radius fluctuations) has been widely studied as a way of analyzing tree responses to the environment, including the phenotypic plasticity of tree–water relationships in particular. However, the genetic basis of this daily phenotype and its interplay with the environment remain largely unexplored. We characterized the genetic and environmental determinants of this response, by monitoring daily stem radius fluctuation (dSRF) on 210 trees from a Eucalyptus urophylla × E. grandis full‐sib family over 2 years. The dSRF signal was broken down into hydraulic capacitance, assessed as the daily amplitude of shrinkage (DA), and net growth, estimated as the change in maximum radius between two consecutive days (ΔR). The environmental determinants of these two traits were clearly different: DA was positively correlated with atmospheric variables relating to water demand, while ΔR was associated with soil water content. The heritability for these two traits ranged from low to moderate over time, revealing a time‐dependent or environment‐dependent complex genetic determinism. We identified 686 and 384 daily quantitative trait loci (QTL) representing 32 and 31 QTL regions for DA and ΔR, respectively. The identification of gene networks underlying the 27 major genomics regions for both traits generated additional hypotheses concerning the biological mechanisms involved in response to water demand and supply. This study highlights that environmentally induced changes in daily stem radius fluctuation are genetically controlled in trees and suggests that these daily responses integrated over time shape the genetic architecture of mature traits.     

Five New C19‐Diterpenoid Alkaloids from Delphinium tianshanicum W.T.Wang

Five new diterpenoid alkaloids, tianshanitines A‐E ( 1  –  5 ), along with ten known compounds ( 6  –  15 ), were isolated from the EtOH extracts of the whole plant of Delphinium tianshanicum W.T.Wang . Their structures were determined based on extensive spectroscopic analyses, including 1D‐ and 2D‐NMR, HR‐ESI‐MS, and the structure of tianshanitine C ( 3 ) was confirmed by X‐ray diffraction analysis. Tianshanitine A ( 1 ) is the first example of natural diterpenoid alkaloid containing a benzoyl group at C(1) position. Tianshanitine B ( 2 ) is a rare natural diterpenoid alkaloid bearing a OH group at C(16) position. Compounds 1  –  5 , 6 , 8 , 10 , 12 and 14 were evaluated for cytotoxicity against HCT116, MCF‐7 and HepG2 human cancer cell lines.