Nuclear rDNA and chloroplast rbcL, rbcS and IGS sequence data, and their implications from the Japanese, Korean, and North American harmful algae, Heterosigma akashiwo (Raphidophyceae)

The toxic Heterosigma akashiwo has been found in coastal environments and its algal blooms have been associated with mass mortality in marine organisms and farmed fish. Over the last two decades, H. akashiwo has expanded its geographical range on a worldwide scale, though all populations are suspected to be a single species. To find strong molecular evidence, supporting this hypothesis we determined nuclear 18S, ITS and LSU rDNA, and chloroplast rbcL, rbcS and flanking IGS sequences from six isolates located in North America, Japan and Korea. We compared individual loci from molecular regions (e.g., 26.7kbp of DNA sequence) and found all the isolates to have an identical genotype. Further, the long sequences allow us to compare all the partial sequences that have been reported from samples obtained in ten countries. All these sequence are nearly identical. This suggests that they have dispersed recently from one location. The sequences revealed here can be used as an additional option for making molecular comparisons of sequences from the same isolate.     

福建水华微囊藻毒素对小鼠免疫细胞影响的体外实验研究

[目的]探讨福建省水华微囊藻毒素对机体免疫细胞的损害.[方法]无菌取小鼠脾细胞和腹腔巨噬细胞,MC-LR染毒剂量均为0、1、5、10 μg/ml,观察MC-LR对小鼠T、B淋巴细胞增殖的影响和MC-LR染毒24、48和72 h对小鼠巨噬细胞增殖的影响.[结果]1、5、10 μg/ml剂量组T淋巴细胞刺激指数(SI)下降;5、10 μg/ml剂量组B淋巴细胞刺激指数下降.染毒48 h,各剂量组腹腔巨噬细胞增殖受到不同程度抑制,其中5、10 μg/ml剂量组抑制增殖明显;染毒72 h,1、5、10 μg/ml剂量组抑制增殖明显,呈现一定的剂量效应关系.[结论]福建省水华微囊藻毒素可以明显抑制小鼠脾T、B淋巴细胞的增殖,损伤特异性免疫功能;还可明显抑制小鼠腹腔巨噬细胞的增殖,损伤非特异性免疫功能.     

Two closely related RecQ helicases have antagonistic roles in homologous recombination and DNA repair in Arabidopsis thaliana

RecQ helicases are involved in the processing of DNA structures arising during replication, recombination, and repair throughout all kingdoms of life. Mutations of different RecQ homologues are responsible for severe human diseases, such as Blooms (BLM) or Werner (WRN) syndrome. The loss of RecQ function is often accompanied by hyperrecombination caused by a lack of crossover suppression. In the Arabidopsis genome seven different RecQ genes are present. Two of them (AtRECQ4A and 4B) arose because of a recent duplication and are still nearly 70% identical on a protein level. Knockout of these genes leads to antagonistic phenotypes: the RECQ4A mutant shows sensitivity to DNA-damaging agents, enhanced homologous recombination (HR) and lethality in a mus81 background. Moreover, mutation of RECQ4A partially suppresses the lethal phenotype of an AtTOP3alpha mutant, a phenomenon that had previously been demonstrated for RecQ homologues of unicellular eukaryotes only. Together, these facts strongly suggest that in plants RECQ4A is functionally equivalent to SGS1 of Saccharomyces cerevisiae and the mammalian BLM protein. In stark contrast, mutants of the closely related RECQ4B are not mutagen-sensitive, not viable in a mus81 background, and unable to suppress the induced lethality caused by loss of TOP3alpha. Moreover, they are strongly impaired in HR. Thus, AtRECQ4B is specifically required to promote but not to suppress crossovers, a role in which it differs from all eukaryotic RecQ homologues known.     

Problems associated with the presence of cyanobacteria in recreational and drinking waters

Eutrophication of waters can lead to the development of blooms of cyanobacteria (blue-green algae) and consequent health and environmental problems. The presence of these organisms in recreational and drinking waters is generally undesirable or even hazardous, although nitrogen fixing blue-green algae can be beneficially used as biofertilisers for plantation crops. This paper reviews the characteristics of cyanobacteria and particularly their toxins. The mechanisms of toxic algal blooms are discussed, as are the factors influencing toxin production. The nuisance and health hazards associated with freshwater bluegreen algae are discussed and the options for public health control are evaluated. The problems associated with statutory control of toxic algae problems is also considered.