Arsenic methylation by an arsenite S-adenosylmethionine methyltransferase from Spirulina platensis

Arsenic-contaminated water is a serious hazard for human health. Plankton plays a critical role in the fate and toxicity of arsenic in water by accumulation and biotransformation.Spirulina platensis(S. platensis), a typical plankton, is often used as a supplement or feed for pharmacy and aquiculture, and may introduce arsenic into the food chain, resulting in a risk to human health. However, there are few studies about how S. platensis biotransforms arsenic. In this study, we investigated arsenic biotransformation by S. platensis. When exposed to arsenite(As(Ⅲ)), S. platensis accumulated arsenic up to 4.1 mg/kg dry weight.After exposure to As(Ⅲ), arsenate(As(Ⅴ)) was the predominant species making up 64% to86% of the total arsenic. Monomethylarsenate(MMA(Ⅴ)) and dimethylarsenate(DMA(Ⅴ))were also detected. An arsenite S-adenosylmethionine methyltransferase from S. platensis(Sp Ars M) was identified and characterized. Sp Ars M showed low identity with other reported Ars M enzymes. The Escherichia coli AW3110 bearing Spars M gene resulted in As(Ⅲ) methylation and conferring resistance to As(Ⅲ). The in vitro assay showed that Sp Ars M exhibited As(Ⅲ) methylation activity. DMA(Ⅴ) and a small amount of MMA(Ⅴ) were detected in the reaction system within 0.5 hr. A truncated Sp Ars M derivative lacking the last 34 residues still had the ability to methylate As(Ⅲ). The three single mutants of Sp Ars M(C59S, C186 S, and C238S) abolished the capability of As(Ⅲ) methylation, suggesting the three cysteine residues are involved in catalysis. We propose that Sp Ars M is responsible for As methylation and detoxification of As(Ⅲ) and may contribute to As biogeochemistry.     

钝顶螺旋藻固定模拟烟道气中的CO2

研究了钝顶螺旋藻对模拟烟道气中CO2的固定性能,及其对NOx和SOx水溶形态亚硝态氮、亚硫酸氢根的耐受性。结果显示:随CO2浓度的增加,藻细胞达到最大比生长速率的时间缩短,CO2浓度为15%时藻细胞比生长速率达到最大的时间最短,生物量最终达到最大值4.1 g/L;CO2浓度为15%时藻细胞的固碳率为12.34 mg/(L·h)。研究发现,钝顶螺旋藻能够耐受浓度小于10 mmol/L的亚硝态氮,可将其作为钝顶螺旋藻生长的唯一氮源,但藻生长的延迟期增长。钝顶螺旋藻能够耐受8 mmol/L的亚硫酸氢盐,可将其作为生长的唯一硫源,藻细胞6 d后开始快速增长。     

Embarking on the Second Green Revolution for Sustainable Agriculture in India: A Judicious Mix of Traditional Wisdom and Modern Knowledge in Ecological Farming

The Green Revolution in India which was heralded in the 1960‘s was a mixed blessing. Ambitious use of agro-chemicals boosted food production but also destroyed the agricultural ecosystem. Of late Indian farmers and agricultural scientists have realized this and are anxious to find alternatives – perhaps a non-chemical agriculture – and have even revived their age-old traditional techniques of natural farming. Scientists are working to find economically cheaper and ecologically safer alternatives to agro-chemicals. Blue-Green Algae Biofertilizers, Earthworm Vermicomposts (Vermiculture), biological control of pests and herbal biopesticides are showing promise. Saline agriculture and sewage farming are also being promoted in India to augment food production in the face of water scarcity. There is a move to search for alternative foods, which are more nutritious, cheaper and have shorter harvest cycles. Farm and food policy in India has to change its outlook before there can be a second green revolution. This revised version was published online in August 2006 with corrections to the Cover Date.     

钝顶螺旋藻处理氨氮废水的研究

螺旋藻是一种营养丰富的新型保健食品，利用含氮废水为培养基，研究螺旋藻以NH4－N的处理效率，着重探讨利用生活污水培养螺旋藻的可行性，及其对生活污水的处理效果。研究证明，在NH4－N浓度小于40.0mg/L时，其对NH4－N的去除率最大，可达93％左右。在体积百分比生活污水为80％时，添加NaHCO38mg/L，对NH4－N的去除率达91.8%。同时对螺旋藻化学组分及含铁、锌、锰、铜、硒进行分析，生活污水培养螺旋藻，其所含有机物和氮源，可供螺旋藻生长繁殖，使废水资源化，并减少环境污染；藻粉可作为饲料添加剂，是使废水变为蛋白源的有效途径。     

钝顶螺旋藻对Cd胁迫的生理反应

研究了钝顶螺旋藻在Cd胁迫下的生理指标的变化.结果表明,在CdCl2浓度为0～24 mg/L范围的Cd胁迫下,随着CdCl2浓度的增加,可溶性蛋白的含量明显低于对照组,抗氧化系统也受到了不同程度的影响.SOD(超氧化物歧化酶)和POD(过氧化物酶)活力呈先增后降趋势,其中POD活力增加的程度较大,最高可达对照的360%,最低也为对照组的262%.在0～24 mg/L浓度范围内,APX(抗坏血酸氧化酶)活力均低于对照组,但随CdCl2浓度的增加呈递增状态.CAT(过氧化氢酶)均高于对照组,整体呈增加的趋势.GSH-PX(谷胱甘肽过氧化物酶)活力均低于对照,最低降至对照组的25%.MDA(丙二醛)作为膜脂质过氧化的产物,其累积是Cd胁迫的突出的生理变化之一,MDA的含量与CdCl2的浓度呈正相关.     

TA（三十烷醇）乳粉对螺旋藻的促长作用及生理调控

研究了TA(三十烷醇 )乳粉对钝顶螺旋藻的生长、光合活性及氮素代谢的影响 .结果表明 ,较低浓度的TA处理 ,可明显促进生长 .经TA浓度为 0 .0 1mg/L的处理后 ,螺旋藻的生长速率提高 12 .4 % ,光合放氧速率提高 2 9.9% .这种生长促进作用可能与TA处理后光合色素含量的明显增加有关 .其中叶绿素a含量提高 18.6 % ,藻蓝素和类胡萝卜素的含量分别提高 5 4 .1%和 38.5 % .研究结果还表明 ,在TA处理后的 2～ 4d内 ,螺旋藻的硝酸还原酶活性可提高2 0 .0 %～ 4 2 .0 % .此外 ,处理组的蛋白质和氨基酸含量也明显高于对照组 .这表明 ,TA乳粉对螺旋藻的氮素代谢也有一定的促进作用 .图 3表 3参 14     

螺旋藻多糖的提取分离纯化及结构初步研究

离心收集处于生长平衡后期的螺旋藻(Spirulinamaxima),通过渗透冲击协同冻融细胞破碎、冷水提取,TCA除蛋白、乙醇沉淀得到粗多糖。用SephadexG 50凝胶层析分离纯化,得到一种水溶性螺旋藻多糖。利用醋酸纤维薄膜电泳和SephadexG 100凝胶检验螺旋藻多糖纯度,证明该糖组分均一。根据红外光谱,元素分析的结果对该糖结构进行初步研究。     

螺旋藻培养与动力学模型

在内循环气升式光生物反应器中，就螺旋藻细胞在不同碳源培养其中的生长行以及藻细胞对光能和碳源的利用特性进行了初步研究，结果表明，向培养体系中通入气体流量1％的CO2，有助于提高经式培养的细胞终浓度和稳定培养体系的PH环境；改进的Lambert-Beer定律可较好地描述细胞浓度及光程对光衰减的综合影响，引入平均光强和平均比消光量概念，探讨了细胞比生长速率与它们之间的关系；藻液中总碳量随细胞浓度的上升呈指数关系减少，藻细胞对碳源的得率系数在批式 不同时期之间存在差异。图12参9     

Antioxidant rich diet supplements (Spirulina and tamarind fruit pulp) mitigate hematological disorders in fluoride exposed mice

The effect of antioxidant rich diet supplements of Spirulina and tamarind fruit pulp at 230 mg kg^?1 body weight, separately as well as in combination, on various hematological parameters of Swiss albino mice exposed to fluoride for seven days at daily doses of 190 mg kg^?1 body weight and for 90 days at daily doses of 94 mg kg^?1 body weight is reported. Compared with controls, fluoride exposure decreased erythrocyte (12%–18%), leukocyte (16%) and platelet counts (7%, only for short-term exposure), hemoglobin (2%–17%) and packed cell volume (2%–14%) in Swiss albino mice reared on standard feed but these were altered little in the diet supplement groups. Fluoride exposure decreased lymphocytes in both standard feed (16%–21%) and diet supplement groups (5%–19%, but only after long-term exposure). Fluoride withdrawal led to recovery of the post-treated mice from long-term exposure. Spirulina alone and also in combination with tamarind fruit pulp was found more effective than tamarind alone in reducing hematological disorders in fluoride treated mice.