Steffen Morgan M, Belisle B Shafer, Watson Sue B, Boyer Gregory L, Bourbonniere Richard A, Wilhelm Steven W
Department of Microbiology, The University of Tennessee, Knoxville, Tennessee, USA.
Water Science and Technology Directorate, Environment Canada, Burlington, ON, Canada.
Appl Environ Microbiol. 2015 May 1;81(9):3268-76. doi: 10.1128/AEM.04101-14. Epub 2015 Feb 6.
Little is known about the molecular and physiological function of co-occurring microbes within freshwater cyanobacterial harmful algal blooms (cHABs). To address this, community metatranscriptomes collected from the western basin of Lake Erie during August 2012 were examined. Using sequence data, we tested the hypothesis that the activity of the microbial community members is independent of community structure. Predicted metabolic and physiological functional profiles from spatially distinct metatranscriptomes were determined to be ≥90% similar between sites. Targeted analysis of Microcystis aeruginosa, the historical causative agent of cyanobacterial harmful algal blooms over the past ∼20 years, as well as analysis of Planktothrix agardhii and Anabaena cylindrica, revealed ongoing transcription of genes involved in microcystin toxin synthesis as well as the acquisition of both nitrogen and phosphorus, nutrients often implicated as independent bottom-up drivers of eutrophication in aquatic systems. Transcription of genes involved in carbon dioxide (CO2) concentration and metabolism also provided support for the alternate hypothesis that high-pH conditions and dense algal biomass result in CO2-limiting conditions that further favor cyanobacterial dominance. Additionally, the presence of Microcystis-specific cyanophage sequences provided preliminary evidence of possible top-down virus-mediated control of cHAB populations. Overall, these data provide insight into the complex series of constraints associated with Microcystis blooms that dominate the western basin of Lake Erie during summer months, demonstrating that multiple environmental factors work to shape the microbial community.
对于淡水蓝藻有害藻华（cHABs）中共存微生物的分子和生理功能，我们所知甚少。为了解决这个问题，我们研究了2012年8月从伊利湖西部流域采集的群落宏转录组。利用序列数据，我们检验了微生物群落成员的活性与群落结构无关这一假设。结果表明，来自空间上不同的宏转录组的预测代谢和生理功能谱在不同位点之间相似度≥90%。对过去约20年中蓝藻有害藻华的历史致病因子铜绿微囊藻进行靶向分析，以及对阿氏浮丝藻和柱状鱼腥藻的分析，揭示了参与微囊藻毒素合成以及氮和磷获取的基因正在转录，而氮和磷通常被认为是水生系统富营养化中独立的自下而上驱动因素。参与二氧化碳（CO2）浓缩和代谢的基因转录也为另一种假设提供了支持，即高pH条件和密集的藻类生物量会导致CO2限制条件，进一步有利于蓝藻占优势。此外，微囊藻特异性噬藻体序列的存在为自上而下的病毒介导控制cHAB种群提供了初步证据。总体而言，这些数据为深入了解与夏季主导伊利湖西部流域的微囊藻华相关的一系列复杂限制因素提供了线索，表明多种环境因素共同作用塑造了微生物群落。
