Growth and removal of nitrogen and phosphorus by free-living and chitosan-immobilized cells of the marine cyanobacterium Synechococcus elongatus

This study investigated the growth rate of chitosan-immobilized cells of the marine cyanobacterium Synechococcus elongatus and its potential application in the removal of nitrogen and phosphorus for wastewater treatment. Immobilized cell cultures had a lag phase of growth due to the immobilization method, and their growth rate was similar to that of free-living cell cultures. Ammonia removal was higher in free cells (54%) than in immobilized cells (29%), but nitrate removal was similar in immobilized (38%) and free cells (44%); phosphorus removal was more efficient in free cells (88%) than in immobilized cells (77%). Chlorophyll a and protein content were higher in immobilized cells. Our study demonstrates that S. elongatus immobilized into chitosan capsules can remove nutrients and is able to maintain a growth rate comparable to that of free cells in culture.     

DIFFERENT PHYSIOLOGICAL RESPONSES OF FOUR MARINE SYNECHOCOCCUS STRAINS (CYANOPHYCEAE) TO NICKEL STARVATION UNDER IRON‐REPLETE AND IRON‐DEPLETE CONDITIONS1

Synechococcus species are important primary producers in coastal and open‐ocean ecosystems. When nitrate was provided as the sole nitrogen source, nickel starvation inhibited the growth of strains WH8102 and WH7803, while it had little effect on two euryhaline strains, WH5701 and PCC 7002. Nickel was required for the acclimation of Synechococcus WH7803 to low iron and high light. In WH8102 and WH7803, nickel starvation decreased the linear electron transport activity, slowed down Q_A reoxidation, but increased the connectivity factor between individual photosynthetic units. Under such conditions, the reduction of their intersystem electron transport chains was expected to increase, and their cyclic electron transport around PSI would be favored. Nickel starvation decreased the total superoxide dismutase (SOD) activity of WH8102 and WH7803 by 30% and 15% of the control, respectively. The protein‐bound ⁶³Ni of the oceanic strain WH8102 comigrated with SOD activity on nondenaturing gels and thus provided additional evidence for the existence of active NiSOD in Synechococcus WH8102. In WH7803, it seems likely that nickel starvation affected other metabolic pathways and thus indirectly affected the total SOD activity.     

N-Acetyl-l-Glutamate Kinase (NAGK) from Oxygenic Phototrophs: PII Signal Transduction across Domains of Life Reveals Novel Insights in NAGK Control

N-Acetyl-l-glutamate kinase (NAGK) catalyzes the first committed step in arginine biosynthesis in organisms that perform the cyclic pathway of ornithine synthesis. In eukaryotic and bacterial oxygenic phototrophs, the activity of NAGK is controlled by the P_II signal transduction protein. Recent X-ray analysis of NAGK-P_II complexes from a higher plant (Arabidopsis thaliana) and a cyanobacterium (Synechococcus elongatus) revealed that despite several differences, the overall structure of the complex is highly similar. The present study analyzes the functional conservation of P_II-mediated NAGK regulation in plants and cyanobacteria to distinguish between universal properties and those that are specific for the different phylogenetic lineages. This study shows that plant and cyanobacterial P_II proteins can mutually regulate the NAGK enzymes across the domains of life, implying a high selective pressure to conserve P_II-NAGK interaction over more than 1.2 billion years of separate evolution. The non-conserved C-terminus of S. elongatus NAGK was identified as an element, which strongly enhances arginine inhibition and is responsible for most of the differences between S. elongatus and A. thaliana NAGK with respect to arginine sensitivity. Both P_II proteins relieve arginine inhibition of NAGK, and in both lineages, P_II-mediated relief from arginine inhibition is antagonized by 2-oxoglutarate. Together, these properties highlight the conserved role of P_II as a signal integrator of the C/N balance sensed as 2-oxoglutarate to regulate arginine synthesis in oxygenic phototrophs.     

塔里木板块西南依格孜牙剖面上泥盆统—下石炭统地层学

塔里木板块西南英吉莎县依格孜牙出露上泥盆统—下石炭统序列。克里塔格组下段以法门阶牙行刺Icriodus alternatus alternatus为特征,中段的Spathognathodus aciedentatus和Polygnathus inornatus属杜内阶上部,上段的Scaphignathus sp.大致相当于维宪阶,可能还包括部分谢尔普霍夫阶。岩相序列表明,从奇自拉夫组紫红色石英砂岩、含砾石英砂岩相变为克里塔格组台地浅海相碳酸盐岩指示一次海进过程,克里塔格组礁灰岩可视为大灭绝事件之后全球最早的珊瑚礁群落复苏代表实例之一。     

Size‐spectrum based differential response of phytoplankton to nutrient and iron‐organic matter combinations in microcosm experiments in a Chilean Patagonian Fjord

The Patagonian fjords have been recognized as a major region of relatively high primary productivity systems during spring–summer bloom periods, where iron‐organic matter forms may be essential complexes involved in key growth processes connected to the carbon and nitrogen cycles. We used two dissolved organic matter (DOM) types, marine polysaccharide and siderophore, as a model to understand how they affect the bioavailability of Fe to phytoplankton and bacteria and to assess their ecological role in fjord systems. A 10‐day microcosm study was performed in the Comau Fjord during summer conditions (March 2012). Pico‐, nano‐, and microphytoplankton abundance, total chlorophyll‐a and bacteria abundance, and bacterial secondary production estimates were analyzed in five treatments: (i) control (no additions), (ii) only nutrients (NUT: PO₄, NO₃, Si), (iii) nutrients + Fe(II), (iv) polysaccharide (natural diatoms extracted: 1–3 beta Glucan), and (v) Hexandentate Desferroxiamine B (DFB, siderophore). Our results showed that while DFB reduced Fe bioavailability for almost all phytoplankton assemblages in the fjord, polysaccharide did not have effects on the iron bioavailability. At Nutrients + Fe and Polysaccharide treatments, chlorophyll‐a concentration abruptly increased from 0.9 to 20 mg m^?3 during the first 4–6 days of the experimental period. Remarkably, at the Nutrients + Fe treatment, the development of the bloom was accompanied by markedly high abundances of Synechococcus, picoeukaryotes, and autotrophic nanoflagellates within the first 4 days of the experiment. Our study indicated that small plankton (phytoplankton <20 μm and bacteria) were the first to respond to dissolved Nutrients + Fe compared to large sized micro‐phytoplankton cells (>20 μm). This could be at least partially attributed to biological utilization of Fe (2 to 3 nM) by <20 μm phytoplankton and bacteria through the interaction with organic ligands released by bacteria that eventually could increase solubility of the Fe dissolved fraction thus having a positive effect on the small‐sized phytoplankton community.     

人尿激酶原基因在聚球藻7002中的克隆和表达

将人尿激酶原基因连在ＰｐｓｂＡ启动子之后,再将启动子连同基因克隆入整合载体ｐＴＺ１８中。ｐＴＺ１８－８中含有一段来源于集胞藻６８０３的ｐｓｂＢ基因片段作为整合平台。将整合表达载体用直接转化的方法转聚球藻Ｓｙｎｅ－ｃｈｏｃｏｃｃｕｓ ｓｐ．ＰＣＣ７００２中。经氨苄青霉素选前扩大培养后的转化进行ＤＮＡ斑点印迹及Ｗｅｓｔｅｒｎ印迹, 基因的存在及表达,菌体破碎后的上清液有较高的溶解纤维蛋白的活性,说明表     

蓝舌病毒HbC株与不同种系细胞相互作用及群特异性抗原特征

BTV-HbC株和蓝舌病毒标准株BTV-10分别接种在不同种系细胞如猴肾传代细胞(Vero)、人宫颈癌细胞(Hela)和小鼠神经胶质瘤细胞(C6)等细胞株上,比较研究了BTV-HbC在不同种系细胞上的增殖特征,BTV-HbC与BTV-10在相同细胞上的复制增殖特征,病毒与细胞相互作用的显微和超微结构特征.用免疫交叉反应研究了BTV-HbC株与BTV-10型标准株之间的血清学关系.本研究结合本室对BTV-HbC株基因组图谱分析和蓝舌病毒群特异性抗原编码基因S7的RT-PCR分析,进一步证实了BTV-HbC株可能是一个新的血清型蓝舌病毒.