Differential expression of the components of the two alkane hydroxylases from Pseudomonas aeruginosa

Oxidation of n-alkanes in bacteria is normally initiated by an enzyme system formed by a membrane-bound alkane hydroxylase and two soluble proteins, rubredoxin and rubredoxin reductase. Pseudomonas aeruginosa strains PAO1 and RR1 contain genes encoding two alkane hydroxylases (alkB1 and alkB2), two rubredoxins (alkG1 and alkG2), and a rubredoxin reductase (alkT). We have localized the promoters for these genes and analyzed their expression under different conditions. The alkB1 and alkB2 genes were preferentially expressed at different moments of the growth phase; expression of alkB2 was highest during the early exponential phase, while alkB1 was induced at the late exponential phase, when the growth rate decreased. Both genes were induced by C(10) to C(22)/C(24) alkanes but not by their oxidation derivatives. However, the alkG1, alkG2, and alkT genes were expressed at constant levels in both the absence and presence of alkanes.     

Na‐Ion Batteries for Large Scale Applications: A Review on Anode Materials and Solid Electrolyte Interphase Formation

The urgent need for optimizing the available energy through smart grids and efficient large‐scale energy storage systems is pushing the construction and deployment of Li‐ion batteries in the MW range which, in the long term, are expected to hit the GW dimension while demanding over 1000 ton of positive active material per system. This amount of Li‐based material is equivalent to almost 1% of current Li consumption and can strongly influence the evolution of the lithium supply and cost. Given this uncertainty, it becomes mandatory to develop an energy storage technology that depends on almost infinite and widespread resources: Na‐ion batteries are the best technology for large‐scale applications. With small working cells in the market that cannot compete in cost ($/W h) with commercial Li‐ion batteries, the consolidation of Na‐ion batteries mainly depends on increasing their energy density and stability, the negative electrodes being at the heart of these two requirements. Promising Na‐based negative electrodes for large‐scale battery applications are reviewed, along with the study of the solid electrolyte interphase formed in the anode surface, which is at the origin of most of the stability problems.     

饲料中添加外源酶对大黄鱼和鲈氮磷排泄的影响

本研究以大黄鱼和鲈为实验对象,探讨饲料中添加植酸酶(PY)和非淀粉性多糖酶(WX和VP)对其氨氮和可溶性磷(PO3-4-P)排泄的影响.以含植物蛋白的饲料为基础饲料,分别向每千克饲料中添加200mg植酸酶(酶的活性为2500IU/g)、 800mg WX(主要包括葡聚糖酶、戊聚糖酶和纤维素酶,各种酶的活性皆为50IU/g)、 400mg VP(主要为木聚糖酶,酶的活性为1000IU/g)以及800mg WX 400mg VP配制出5种实验饲料.实验鱼在海水网箱中经过8周的摄食驯养后,转入室内水族箱中进行氮磷排泄测定实验.在水族箱中经2天的适应后,测定饥饿状态下氨氮及可溶性磷的排泄率.然后饱食投喂,并连续测定摄食后48h内鱼体氨氮和可溶性磷的排泄率.实验期间水温为26.5-32.5℃,盐度为32.5‰-36‰,溶氧在7 mg/L以上.实验结果表明,饥饿状态下实验鱼的氨氮和可溶性磷排泄不受实验饲料影响(p>0.05).而在饱食条件下,实验饲料中添加非淀粉性多糖酶(WX、VP及WX VP)显著降低了实验鱼的氨氮排泄率(p<0.05),而添加植酸酶组实验鱼的氨氮排泄率与对照组差异不显著.饲料处理对实验鱼可溶性磷的排泄率的影响不显著(p>0.05),但添加植酸酶组实验鱼的可溶性磷排泄率有增加的趋势.     

First phylogeny of predatory flower flies (Diptera, Syrphidae, Syrphinae) using mitochondrial COI and nuclear 28S rRNA genes: conflict and congruence with the current tribal classification

The family Syrphidae (Diptera) is traditionally divided into three subfamilies. The aim of this study was to address the monophyly of the tribes within the subfamily Syrphinae (virtually all with predaceous habits), as well as the phylogenetic placement of particular genera using molecular characters. Sequence data from the mitochondrial protein-coding gene cytochrome c oxidase subunit I ( COI ) and the nuclear 28S ribosomal RNA gene of 98 Syrphinae taxa were analyzed using optimization alignment to explore phylogenetic relationships among included taxa. Volucella pellucens was used as outgroup, and representatives of the tribe Pipizini (Eristalinae), with similar larval feeding mode, were also included. Congruence of our results with current tribal classification of Syrphinae is discussed. Our results include the tribe Toxomerini resolved as monophyletic but placed in a clade with genera Ocyptamus and Eosalpingogaster . Some genera traditionally placed into Syrphini were resolved outside of this tribe, as the sister groups to other tribes or genera. The tribe Bacchini was resolved into several different clades. We recovered Paragini as a monophyletic group, and sister group of the genus Allobaccha . The present results highlight the need of a reclassification of Syrphinae.
© The Willi Hennig Society 2008.     

Factors controlling the colonial structure of <Emphasis Type="Italic">Pediastrum tetras</Emphasis> (Chlorophyceae)

Accounting for morphological plasticity in phytoplankton populations is relevant for taxonomy, systematic/evolutionary, and ecological studies. In this work, the green alga Pediastrum tetras (Ehrenberg) Ralfs was used to describe the variation in population size structure over its growth cycle and to analyze responses to changes in biotic and abiotic factors. Pediastrum cultures reached a final stable concentration in approximately 10 days. This density (8 × 10⁵ cells ml⁻¹) remained stable for at least another 13 days and the intrinsic growth rate was 0.24 ± 0.01 day⁻¹. In the exponential phase, the relative number of single cells and the proportion of large cells (with vesicles inside) within colonies increased. When density peaked, a relative increase of single cells as well as small cells in new colonies took place. Finally, during the stationary phase, the trend reversed: fewer single cells and a larger cell size (without vesicles) were observed. Results indicated that nutrient supply could affect population structure, diminishing the proportion of eight-cell colonies. Daphnia magna Straus significantly reduced the Pediastrum population density due to predation, and this led to a significant decrease in the density of the largest colonies. In addition, info-chemicals induced a slight increase in the density of the largest colonies compared to the control treatment. Our study suggests a possible trade-off in P. tetras colonial size in natural environments: during the stationary growth period in a lake, Pediastrum populations tend to increase in size for efficient use of nutrients, while they decrease in size in the presence of herbivores. Handling editor: J. Padisak     

瓜实蝇的有效积温及其在中国的年发生代数预测

瓜实蝇Bactrocera cucurbitae Coquillett是世界上重要的检疫性害虫,通过在14、18、22、26、30、34℃温度下孵化和饲养实验,测定该虫卵、幼虫、蛹、产卵前期、世代的发育起点温度和有效积温分别是8．0982℃、4．5245℃、4．5245℃、7．4751℃、10．0019℃和28．8506、162．7462、145．7249、166．5126、503．8343日度。根据该虫的致死温度和有效积温模型,运用数学分析和地理信息系统技术,预测了瓜实蝇在中国的适生区和年发生代数,结果表明：该虫可在中国48．96％地区发生（气象站点所代表的地区）,1年发生2-12代,以4～6代为主。