Department of Botany, Faculty of Science, Sohag University, Sohag 82524, Egypt.
Toxicon. 2010 Jun 15;55(7):1346-52. doi: 10.1016/j.toxicon.2010.02.007. Epub 2010 Feb 16.
Cyanotoxins have been largely studied in planktonic and benthic cyanobacteria, but microcystin (MCYST) production in epiphytic cyanobacteria has not been reported yet. The present study reports for the first time the MCYST production in epiphytic cyanobacteria on submerged macrophytes. During this study, four common submerged macrophytes in eutrophic pond in Saudi Arabia were surveyed for the presence of toxic epiphytic cyanobacteria. The results showed that chlorophyll-a and total biovolume of epiphytic cyanobacteria differed significantly among submerged plants with highest values obtained in Stratiotes aloides and lowest in Elodea canadensis. Epiphytic materials collected from Ceratophyllum demersum and S. aloides had higher species diversities than materials collected from E. canadensis and Myriophyllum verticillatum. The cyanobacteria, Merismopedia tenuissima and Leptolyngbya boryana were recorded with a high abundance in epiphytic materials collected from all submerged macrohpytes. Based on Enzyme-linked immunosorbent assay (ELISA), these two species were found to produce MCYSTs (MCYSTs) with concentrations of 1438 and 630 microg g(-1) dry weight, respectively. HPLC analysis of the methanolic extracts of the two species showed that M. tenuissima extract contained MCYST-RR and -LR/demethyl LR plus 3 minor unidentified MCYSTs, while L. boryana extract contained MCYST-YR, -LR/demethyl LR, and 2 minor unidentified MCYSTs. This study suggests that epiphytic species should be considered during monitoring of toxic cyanobacteria in water sources.
蓝藻毒素在浮游和底栖蓝藻中得到了广泛研究，但附着性蓝藻产生微囊藻毒素（MCYST）的情况尚未报道。本研究首次报道了附着在水生植物上的附着性蓝藻产生 MCYST。在本研究中，对沙特富营养化池塘中的四种常见沉水植物进行了调查，以确定是否存在有毒的附着性蓝藻。结果表明，附着性蓝藻的叶绿素-a 和总生物量在沉水植物之间存在显著差异，其中 Stratiotes aloides 中的值最高，Elodea canadensis 中的值最低。从 Ceratophyllum demersum 和 S. aloides 收集的附着材料的物种多样性高于从 E. canadensis 和 Myriophyllum verticillatum 收集的材料。Merismopedia tenuissima 和 Leptolyngbya boryana 这两种蓝藻在所有附着在沉水植物上的材料中都有较高的丰度。基于酶联免疫吸附测定（ELISA），发现这两种蓝藻都产生 MCYST（MCYSTs），浓度分别为 1438 和 630 μg g(-1) 干重。对两种蓝藻甲醇提取物的 HPLC 分析表明，M. tenuissima 提取物含有 MCYST-RR 和 -LR/去甲基 LR 加 3 种未鉴定的 MCYSTs，而 L. boryana 提取物含有 MCYST-YR、-LR/去甲基 LR 和 2 种未鉴定的 MCYSTs。本研究表明，在监测水源中有毒蓝藻时，应考虑附着性物种。
