Isolation and Characterization of Rhizophydiales (Chytridiomycota), Obligate Parasites of Planktothrix agardhii in a Laurentian Great Lakes Embayment
Isolation and Characterization of Rhizophydiales (Chytridiomycota), Obligate Parasites of Planktothrix agardhii in a Laurentian Great Lakes Embayment
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DOI：
10.1128/aem.02308-20
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发表时间：
2021-02-01
影响因子：
4.4
通讯作者：
Bullerjahn, George S.
中科院分区：
文献类型：
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作者：
McKindles, Katelyn M.;Jorge, Alejandro N.;Bullerjahn, George S.
从5月到9月，美国伊利湖桑达斯基湾的蓝藻水华群落中，阿加尔氏浮游丝菌占主导地位。这种丝状蓝藻是一种已知的专性寄生虫，壶菌Rhizophydium sp.的宿主。在2018年的水华季节，通过利用稀释和单丝分离技术，从桑达斯基湾分离出7种壶菌和12种P. agardhii菌株。这7个壶菌和选择的P. agardhii主机，然后就感染率进行了表征。感染孤立的壶菌是特定的浮游发菌属物种，并没有发现其他丝状蓝藻类群存在于海湾（Aphanizomenon属和Cuspidothrix属）。即使在潜在的P. agardhii宿主菌株中，单个壶菌分离株也具有不同程度的感染性，并对不同的宿主分离株表现出偏好，这表明即使在相同的样品群体中也可能存在生态分区。当壶菌致病机制进行了研究，游动孢子显示了一个群集模式，攻击和断裂的主机丝，并在毛状体末端创建新的感染部位。这些寄生壶菌的感染也导致从宿主细胞内释放微囊藻毒素。此外，感染依赖于培养基类型，突出了培养基选择对实验结果的重要性。观察到壶菌群集的介质与自然环境的离子强度密切匹配。了解真菌寄生虫的发病机制将有助于未来的努力，以确定有利于损失机制的环境因素为Planktothrix agardhii为主blooms.IMPORTANCE虽然许多研究都集中在蓝藻有害藻华（cHABs）的建立和持久性的因素，很少有研究探讨了水华的发病机制。壶菌感染蓝细菌，并通过操纵以前难以消化的细丝和释放营养物质来支持异养微生物来刺激食物网相互作用。具体而言，感染丝状浮游发菌agardhii的壶菌表现出种特异性感染，将毛状体碎片化成更容易被食草动物消耗的较短单位。壶菌游动孢子也是低级食物网的优质食物来源。了解宿主-病原体关系和蓝藻的致病机制将是必要的，有效地模拟cHABs的生态。
Planktothrix agardhii dominates the cyanobacterial harmful algal bloom community in Sandusky Bay, Lake Erie (USA), from May through September. This filamentous cyanobacterium is host to a known obligate parasite, the chytrid Rhizophydium sp. During the 2018 bloom season, by utilizing dilution and single-filament isolation techniques, 7 chytrid and 12 P. agardhii strains were isolated from Sandusky Bay. These 7 chytrids and a selection of P. agardhii hosts were then characterized with respect to infection rates. Infections by the isolated chytrids were specific to Planktothrix planktonic species and were not found on other filamentous cyanobacterial taxa present in the bay (Aphanizomenon sp. and Cuspidothrix sp.). Even among the potential P. agardhii host strains, individual chytrid isolates had different degrees of infectivity and showed preferences for different host isolates, suggesting possible ecological partitioning even within the same sample population. When mechanisms of chytrid pathogenesis were examined, the zoospores displayed a swarming pattern to attack and fracture the host filament and create new infection sites at the trichome termini. Infections by these parasitic chytrids also led to a release of intracellular microcystin toxins from the hosts. Additionally, infections were dependent on medium type, highlighting the importance of medium choice for experimental outcomes. Media in which chytrid swarming was observed closely matched the ionic strength of the natural environment. Understanding pathogenesis by fungal parasites will assist future efforts to determine environmental factors favoring loss mechanisms for Planktothrix agardhii-dominated blooms.IMPORTANCE Whereas many studies have focused on the factors contributing to the establishment and persistence of cyanobacterial harmful algal blooms (cHABs), few studies have examined bloom pathogenesis. Chytrid fungi infect cyanobacteria and stimulate food web interactions through manipulation of previously hard-to-digest filaments and the release of nutrients to support heterotrophic microbes. Specifically, chytrids infective for filamentous Planktothrix agardhii exhibit a species-specific infection that fragments trichomes into shorter units that can be consumed more easily by grazers. Chytrid zoospores also serve as a high-quality food source for the lower food web. Understanding host-pathogen relationships and mechanisms of pathogenesis on cyanobacteria will be necessary to effectively model the ecology of cHABs.