Zheng Qiang, Lin Wenxin, Wang Yu, Xu Dapeng, Liu Yanting, Jiao Nianzhi
State Key Laboratory for Marine Environmental Science, Institute of Marine Microbes and Ecospheres, College of Ocean and Earth Sciences, Xiamen University, Xiamen, People's Republic of China.
Fujian Key Laboratory of Marine Carbon Sequestration, Xiamen University, Xiamen, People's Republic of China.
Mol Ecol. 2021 Jan;30(2):592-607. doi: 10.1111/mec.15750. Epub 2020 Dec 6.
Viral lysis and protistan grazing are thought to be the major processes leading to microbial mortality in aquatic environments and thus regulate community diversity and biogeochemical cycling characteristics. Here, we studied nutrient cycling and bacterial responses to cyanophage-mediated photoautotroph lysis and ciliate predation in a model Synechococcus-heterotroph co-culture system. Both viral lysis and Euplotes grazing facilitated the transformation of organic carbon from biomass to dissolved organic matter with convention efficiencies of 20%-26%. The accumulation of ammonium after the addition of phages and ciliates suggested the importance of recycled NH occurred in the interactions between Synechococcus growth and heterotrophic bacterial metabolism of photosynthate. The slower efficiency of P mineralization compared to N (primarily ammonium) indicated that P-containing organic matter was primarily integrated into bacterial biomass rather than being remineralized into inorganic phosphate under C-rich conditions. In the cyanophage addition treatment, both Fluviicola and Alteromonas exhibited rapid positive responses to Synechococcus lysing, while Marivita exhibited an apparent negative response. Further, the addition of Euplotes altered the incubation system from a Synechococcus-driven phycosphere to a ciliate-remodelled zoosphere that primarily constituted grazing-resistant bacteria and Euplotes symbionts. Top-down controls increased co-culture system diversity and resulted in a preference for free-living lifestyles of dominant populations, which was accompanied by the transfer of matter and energy. Our results indicate top-down control was particularly important for organic matter redistribution and inorganic nutrient regeneration between photoautotrophs and heterotrophs, and altered bacterial lifestyles. This study consequently sheds light on marine biogeochemical cycling and the interaction networks within these dynamic ecosystems.
病毒裂解和原生生物捕食被认为是导致水生环境中微生物死亡的主要过程，因此调节着群落多样性和生物地球化学循环特征。在此，我们在一个集球藻-异养菌共培养模型系统中，研究了营养物质循环以及细菌对噬藻体介导的光合自养生物裂解和纤毛虫捕食的反应。病毒裂解和真核纤毛虫捕食都促进了有机碳从生物量向溶解有机物的转化，转化效率为20%-26%。添加噬菌体和纤毛虫后铵的积累表明，在集球藻生长与光合产物异养细菌代谢之间的相互作用中，氮（主要是铵）的循环利用具有重要意义。与氮（主要是铵）相比，磷矿化效率较低，这表明在富碳条件下，含磷有机物主要整合到细菌生物量中，而不是再矿化为无机磷酸盐。在添加噬藻体的处理中，弗卢维icola菌属和交替单胞菌属对集球藻裂解均表现出快速的阳性反应，而海栖菌属则表现出明显的阴性反应。此外，添加真核纤毛虫将培养系统从集球藻驱动的藻际环境转变为纤毛虫重塑的动质体环境，该环境主要由抗捕食细菌和真核纤毛虫共生体组成。自上而下的控制增加了共培养系统的多样性，并导致优势种群偏好自由生活方式，同时伴随着物质和能量的转移。我们的结果表明，自上而下的控制对于光合自养生物和异养生物之间的有机物质再分配和无机养分再生尤为重要，并改变了细菌的生活方式。因此，本研究揭示了海洋生物地球化学循环以及这些动态生态系统中的相互作用网络。
