Assessing the contribution of diazotrophs to microbial Fe uptake using a group specific approach in the Western Tropical South Pacific Ocean.
Assessing the contribution of diazotrophs to microbial Fe uptake using a group specific approach in the Western Tropical South Pacific Ocean.
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DOI：
10.1038/s43705-022-00122-7
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发表时间：
2022-04-27
期刊：
影响因子：
--
通讯作者：
Bonnet, S.
中科院分区：
文献类型：
--
作者：
Lory, C.;Van Wambeke, F.;Fourquez, M.;Barani, A.;Guieu, C.;Tilliette, C.;Marie, D.;Nunige, S.;Berman-Frank, I.;Bonnet, S.
在贫营养海洋中，固氮生物通常受到铁（Fe）可用性的限制。热带南太平洋西部（WTSP）海洋被认为是一个强烈的N2固定区，由于铁肥通过浅热液活动。然而，固氮生物在其自然栖息地，在那里他们与其他微生物共存也需要铁的铁需求，仍然未知。在这里，我们开发和应用的方法组成的耦合55铁摄取实验与细胞分选流式细胞术，并提供组特定的利率原位铁吸收的微生物群落在WTSP中，除了散装和大小分级率。我们发现，固氮菌Crocosphaera沃森和束毛藻的贡献很大的散装原位铁的吸收（~33%，平均在所研究的区域），尽管在数值上不太丰富相比，其余的浮游生物群落。束毛藻的细胞特异性铁吸收速率最高，其次是C. watsonii，微真核生物，原绿球藻，聚球藻，最后是异养细菌。计算的Fe：C配额较高（2至52倍）的研究固氮生物相比，非固氮浮游生物，反映了其高内在的铁需求。这转化为固氮生物地理分布，似乎是由周围的溶解铁浓度的WTSP的影响。尽管具有较低的细胞特异性吸收率，原绿球藻和异养细菌在很大程度上是本体铁吸收的主要贡献者（分别为~23%和~ 12%）。总的来说，这种组特异性的方法增加了我们的能力，检查功能组的生理生态作用，包括那些不太丰富和/或不太活跃的微生物。
Diazotrophs are often limited by iron (Fe) availability in the oligotrophic ocean. The Western Tropical South Pacific (WTSP) ocean has been suggested as an intense N2 fixation area due to Fe fertilizations through shallow hydrothermal activity. Yet, the Fe demand of diazotrophs in their natural habitat, where they cohabit with other microbial organisms also requiring Fe, remains unknown. Here we develop and apply a method consisting of coupling 55Fe uptake experiments with cell-sorting by flow cytometry, and provide group-specific rates of in situ Fe uptake by the microbial community in the WTSP, in addition to bulk and size fractionation rates. We reveal that the diazotrophs Crocosphaera watsonii and Trichodesmium contribute substantially to the bulk in situ Fe uptake (~33% on average over the studied area), despite being numerically less abundant compared to the rest of the planktonic community. Trichodesmium had the highest cell-specific Fe uptake rates, followed by C. watsonii, picoeukaryotes, Prochlorococcus, Synechococcus and finally heterotrophic bacteria. Calculated Fe:C quotas were higher (by 2 to 52-fold) for both studied diazotrophs compared to those of the non-diazotrophic plankton, reflecting their high intrinsic Fe demand. This translates into a diazotroph biogeographical distribution that appears to be influenced by ambient dissolved Fe concentrations in the WTSP. Despite having low cell-specific uptake rates, Prochlorococcus and heterotrophic bacteria were largely the main contributors to the bulk Fe uptake (~23% and ~12%, respectively). Overall, this group-specific approach increases our ability to examine the ecophysiological role of functional groups, including those of less abundant and/or less active microbes.
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