Accumulation and Dissolution of Magnetite Crystals in a Magnetically Responsive Ciliate
Accumulation and Dissolution of Magnetite Crystals in a Magnetically Responsive Ciliate
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DOI：
10.1128/aem.02865-17
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发表时间：
2018-04-01
影响因子：
4.4
通讯作者：
Lefevre, Christopher T.
中科院分区：
文献类型：
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作者：
Monteil, Caroline L.;Menguy, Nicolas;Lefevre, Christopher T.
趋磁细菌（MTB）是一类广泛存在于水生环境中的微生物，在缺氧-缺氧界面上大量繁殖。它们能够吸收高浓度的铁，这要归功于它们独特的细胞器（所谓的磁小体链）中磁性晶体的生物矿化作用。虽然它们的生物多样性已被深入研究，但它们的生态和对铁循环的影响在很大程度上仍未被探索。原生动物的捕食被认为是可能参与铁释放回生态系统的生态过程之一。磁性原生动物以前观察到在水生环境中，但它们的多样性和命运的颗粒铁在放牧过程中的记录很少。在这项研究中，我们报告的磁响应MTB放牧原生动物能够摄取大量的MTB的形态和分子特征。这种原生动物暂时被鉴定为海洋尾丝藻（Uronema marinum），一种已知是细菌捕食者的纤毛虫。使用光学和电子显微镜，我们详细研究了空泡中发生的吞噬原核细胞的溶解。我们对排列的磁小体链和晶体的持续溶解进行了高分辨率的观察。纤毛虫中的颗粒铁约占其总体积的0.01%。我们在其他类型的环境中，这种相互作用的无处不在，并描述不同的放牧策略。这些数据有助于越来越多的证据表明，MTB和原生动物之间的相互作用可能会发挥显着的作用，在microaerophilic habitudes.IMPORTANCE铁周转确定每个地球化学循环的参与者是一个先决条件，我们了解生态系统功能。趋磁细菌（MTB）通过将大量生物矿化的铁矿物集中在其细胞中参与铁循环，这影响了其在水生生境中的缺氧-缺氧过渡区或以下的化学环境。结果表明，一些原生动物栖息在这个生态位可以成为磁性的磁性晶体的摄食生物矿化的放牧MTB。在这项研究中，我们表明，磁性MTB食草动物通常在海洋和淡水沉积物中观察到，有时可以积累非常大量的颗粒铁。我们在这里描述不同的吞噬策略，确定使用磁性颗粒MTB作为示踪剂后，他们的原生动物摄入。这项研究为使用MTB食草动物作为磁小体超微粒子的潜在科学或医学应用铺平了道路。
Magnetotactic bacteria (MTB) represent a group of microorganisms that are widespread in aquatic habitats and thrive at oxic-anoxic interfaces. They are able to scavenge high concentrations of iron thanks to the biomineralization of magnetic crystals in their unique organelles, the so-called magnetosome chains. Although their biodiversity has been intensively studied, their ecology and impact on iron cycling remain largely unexplored. Predation by protozoa was suggested as one of the ecological processes that could be involved in the release of iron back into the ecosystem. Magnetic protozoa were previously observed in aquatic environments, but their diversity and the fate of particulate iron during grazing are poorly documented. In this study, we report the morphological and molecular characterizations of a magnetically responsive MTB-grazing protozoan able to ingest high quantities of MTB. This protozoan is tentatively identified as Uronema marinum, a ciliate known to be a predator of bacteria. Using light and electron microscopy, we investigated in detail the vacuoles in which the lysis of phagocytized prokaryotes occurs. We carried out high-resolution observations of aligned magnetosome chains and ongoing dissolution of crystals. Particulate iron in the ciliate represented approximately 0.01% of its total volume. We show the ubiquity of this interaction in other types of environments and describe different grazing strategies. These data contribute to the mounting evidence that the interactions between MTB and protozoa might play a significant role in iron turnover in microaerophilic habitats.IMPORTANCE Identifying participants of each biogeochemical cycle is a prerequisite to our understanding of ecosystem functioning. Magnetotactic bacteria (MTB) participate in iron cycling by concentrating large amounts of biomineralized iron minerals in their cells, which impacts their chemical environment at, or below, the oxic-anoxic transition zone in aquatic habitats. It was shown that some protozoa inhabiting this niche could become magnetic by the ingestion of magnetic crystals biomineralized by grazed MTB. In this study, we show that magnetic MTB grazers are commonly observed in marine and freshwater sediments and can sometimes accumulate very large amounts of particulate iron. We describe here different phagocytosis strategies, determined using magnetic particles from MTB as tracers after their ingestion by the protozoa. This study paves the way for potential scientific or medical applications using MTB grazers as magnetosome hyperaccumulators.