作者机构：
[魏文学; 吴金水; 秦红灵; 朱亦君] Key Laboratory of Agroecological Processes in Subtropical Region, Institute of Subtropical Agriculture, Chinese Academy of Sciences, Changsha 410125, China;State Key Laboratory of Forest and Soil Ecology, Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang 110164, China;Graduate University of Chinese Academy of Sciences, Beijing 100049, China;[舒荣波] College of Resource and Environment, Hunan Agricultural University, Changsha 410128, China;[李明德] Institute of Soil and Fertilizer, Hunan Academy of Agricultural Sciences, Changsha 410125, China
通讯机构：
[Qin, H.-L.] K;Key Laboratory of Agroecological Processes in Subtropical Region, , Changsha 410125, China
摘要：
The volatile microbial metabolite 2-methylisoborneol (2-MIB) is a root cause of taste and odor issues in freshwater. Although current evidence suggests that 2-MIB is not toxic, this compound degrades water quality and presents problems for water treatment. To address these issues, cyanobacteria and actinomycetes, the major producers of 2-MIB, have been investigated extensively. In this study, two 2-MIB producing strains, coded as Pseudanabaena sp. and Planktothricoids raciborskii, were used in order to elucidate the genetic background, light regulation, and biochemical mechanisms of 2-MIB biosynthesis in cyanobacteria. Genome walking and PCR methods revealed that two adjacent genes, SAM-dependent methyltransferanse gene and monoterpene cyclase gene, are responsible for GPP methylation and subsequent cyclization to 2-MIB in cyanobacteria. These two genes are located in between two homologous cyclic nucleotide-binding protein genes that may be members of the Crp-Fnr regulator family. Together, this sequence of genes forms a putative operon. The synthesis of 2-MIB is similar in cyanobacteria and actinomycetes. Comparison of the gene arrangement and functional sites between cyanobacteria and other organisms revealed that gene recombination and gene transfer probably occurred during the evolution of 2-MIB-associated genes. All the microorganisms examined have a common origin of 2-MIB biosynthesis capacity, but cyanobacteria represent a unique evolutionary lineage. Gene expression analysis suggested that light is a crucial, but not the only, active regulatory factor for the transcription of 2-MIB synthesis genes. This light-regulated process is immediate and transient. This study is the first to identify the genetic background and evolution of 2-MIB biosynthesis in cyanobacteria, thus enhancing current knowledge on 2-MIB contamination of freshwater.
作者机构：
湖南农业大学资源环境学院,湖南,长沙,410128;湖南农业大学农业环境保护研究所,湖南,长沙,410128;中国环境科学研究院,北京,100012;[韩宝禄] College of Resource and Environment, Hunan Agricultural University, Changsha 410128, China, Chinese Research Academy of Environmental Sciences, Beijing 100012, China;[伍一红; 龚道新; 谢惠; 彭筱] College of Resource and Environment, Hunan Agricultural University, Changsha 410128, China, Institute of Agricultural Environmental Protection, Hunan Agricultural University, Changsha 410128, China
通讯机构：
[Gong, D.] C;College of Resource and Environment, Hunan Agricultural University, China
摘要：
To define the molecular response of Acidithiobacillus ferrooxidans under pH up-shift, temporal gene expression profiles were examined by using whole-genome DNA microarrays for A. ferrooxidans. Approximately 30% of the 3,132 genes represented on the microarray were significantly upregulated over a 160-min period, while about 14% were significantly downregulated. Our results revealed that A. ferrooxidans showed potential self-protection and self-regulation performance in response to pH up-shift stress. Many genes involved in regulation of membrane components were differentially expressed under the pH up-shift stress. Likewise, most of genes involved in phosphate metabolism, sulfur assimilation, and CO2 fixation were obviously induced. Conversely, the transcription of a polyphosphate kinase gene (AFE1210) associated with phosphate storage was significantly repressed, which probably stemmed from the depletion of polyphosphate. Besides, most of the genes involved in hydrogen uptake were significantly induced, whereas many genes involved in nitrogen fixation were obviously repressed, which suggested that hydrogen uptake and nitrogen fixation could contribute to cytoplasmic pH homeostasis.
摘要：
BACKGROUND, AIM, AND SCOPE: Ferro-cyanide is one of the commonly found species at cyanide-contaminated soils and groundwater. Unlike botanical metabolism of KCN via the beta-cyanoalanine pathway, processes involved in the plant-mediated assimilation of ferro-cyanide are still unclear. The objective of this study was to investigate a possible mechanism involved in uptake and assimilation of ferro-cyanide by plants. MATERIALS AND METHODS: Detached roots of plants were exposed to ferro-cyanide in a closed-dark hydroponic system amended with HgCl(2), AgNO(3), LaCl(3), tetraethylammonium chloride (TEACl), or Na(3)VO(4), respectively, at 25 +/- 0.5 degrees C for 24 h. Total CN, free CN(-), and dissolved Fe(2+) were analyzed spectrophotometrically. Activity of beta-cyanoalanine synthase involved in cyanide assimilation was also assayed using detached roots of plants in vivo. RESULTS: Dissociation of ferro-cyanide [Fe(II)(CN)(6)](-4) to free CN(-) and Fe(2+) in solution was negligible. The applied inhibitors did not show any significant impact on the uptake of ferro-cyanide by soybean (Glycine max L. cv. JD 1) and hybrid willows (Salix matsudana Koidz x alba L.; p > 0.05), but rice (Oryza sativa L. cv. JY 98) was more susceptible to the inhibitors compared with the controls (p < 0.05). However, TEACl had the most severe effect on the assimilation of ferro-cyanide by soybean, hybrid willows, and maize (Zea mays L. cv. PA 78; p < 0.01), whereas AgNO(3) was the most sensitive inhibitor to rice (p < 0.01). No measurable difference in beta-cyanoalanine synthase activity of roots exposed to ferro-cyanide was observed compared with the control without any cyanides (p > 0.05), whereas roots exposed to KCN showed a considerable increase in enzyme activity (p < 0.05). CONCLUSIONS: Plants take up Fe(2+) and CN(-) as a whole complex, and in vivo dissociation to free CN(-) is not prerequisite during the botanical assimilation of ferro-cyanide. Ferro-cyanide is likely metabolized by plants directly through an unknown pathway rather than the beta-cyanoalanine pathway.
作者机构：
[向艳文] Soil and Fertilizer Institute of Hunan Province, Changsha 410125, China;College of Resources and Environment, Hunan Agricultural University, Changsha 410128, China;Ministry of Agriculture, Key Field Monitoring Experimental Station for Reddish Paddy Soil Eco-environment in Wangcheng, Changsha 410125, China;[Yang Z.-P.; 廖育林] Soil and Fertilizer Institute of Hunan Province, Changsha 410125, China, College of Resources and Environment, Hunan Agricultural University, Changsha 410128, China, Ministry of Agriculture, Key Field Monitoring Experimental Station for Reddish Paddy Soil Eco-environment in Wangcheng, Changsha 410125, China;[郑圣先; 聂军] Soil and Fertilizer Institute of Hunan Province, Changsha 410125, China, Ministry of Agriculture, Key Field Monitoring Experimental Station for Reddish Paddy Soil Eco-environment in Wangcheng, Changsha 410125, China
通讯机构：
[Nie, J.] S;Soil and Fertilizer Institute of Hunan Province, Changsha 410125, China
摘要：
Two highly water-soluble amino acids,which derived fromβ-CDs,i.e.,glutamic acid-β-cyclodextrin(GluCD)and ethylene-diamine-β-cyclodextrin(EDCD),were synthesized and were examined for their effect on solubilization of anthracene(ANT),complexation of cadmium(Cd~(2+)),and elution removal of ANT and Cd~(2+)in soil.The results showed that GluCD and EDCD were powerful complexant for ANT and Cd~(2+).In the presence of 10 g/L GluCD and EDCD,the solubilization of ANT increased by 47.04 and 23.85 times compared to the control,respectively.GluCD resulted in approximately 90%complexation of Cd~(2+)while 70%complexation was observed for EDCD.Simultaneously,GluCD and EDCD could greatly enhance the elution removal of ANT and Cd~(2+)from soil.GluCD resulted in the highest elution effciency of ANT and Cd~(2+).With the addition of 10 g/L GluCD,53.5%of ANT and 85.6%of Cd~(2+)were eluted,respectively.The ANT had a negligible effect on the Cd~(2+)removal due to different complexing sites of ANT and Cd~(2+),while Cd~(2+)enhanced the ANT removal under the addition of GluCD because Cd~(2+)neutralized the-COOH group of GluCD.Adversely,the removal of ANT was decreased with Cd~(2+)under the addition of EDCD,this was due to the fact that Cd~(2+)enhanced the polarity of EDCD molecule and inhibited the complexation between ANT and EDCD.The study suggested that GluCD could be preferred and be successfully applied to remediation of heavy metals or organic compounds in contaminated soil
摘要：
In order to explore the mechanism of acute toxicity for pyrene to cyanobacterial organisms, the responses of Synechocystis sp. PCC 6803 photosystem II (PS II) under pyrene stress were studied. The results showed there was no significant difference about the oxygen evolution under 0.125 mg/L pyrene stress when compared with control, but it was significantly lower than control at 0.625 mg/L pyrene. Polyphasic chlorophyll-a fluorescence transients in cells of Synechocystis sp. PCC 6803 exhibited a typical increase including O, J, I, and P phases. Fluorescence yield at phases J, I and P declined slightly at 0.125 and 0.625 mg/L pyrene, and significantly lower than control at 3.125 mg/L. According to the parameters deviated from JIP-test, no modification was induced by pyrene both at the donor side and at the acceptor side of PS II, and the reaction centre of PS II is the primary damaging target. Based on the expressing of four key genes (psbA, psbB, psbC and psbO) of PS II, only psbA showed significant difference at 3.125 mg/L pyrene when compared with control.
