Alexander Harriet, Jenkins Bethany D, Rynearson Tatiana A, Dyhrman Sonya T
Massachusetts Institute of Technology-Woods Hole Oceanographic Institution Joint Program in Oceanography/Applied Ocean Science and Engineering, Cambridge, MA 02139; Biology Department, Woods Hole Oceanographic Institution, Woods Hole, MA 02543;
Graduate School of Oceanography, University of Rhode Island, Narragansett, RI 02882; Department of Cell and Molecular Biology, University of Rhode Island, Kingston, RI 02881; and.
Proc Natl Acad Sci U S A. 2015 Apr 28;112(17):E2182-90. doi: 10.1073/pnas.1421993112. Epub 2015 Apr 13.
Diverse communities of marine phytoplankton carry out half of global primary production. The vast diversity of the phytoplankton has long perplexed ecologists because these organisms coexist in an isotropic environment while competing for the same basic resources (e.g., inorganic nutrients). Differential niche partitioning of resources is one hypothesis to explain this "paradox of the plankton," but it is difficult to quantify and track variation in phytoplankton metabolism in situ. Here, we use quantitative metatranscriptome analyses to examine pathways of nitrogen (N) and phosphorus (P) metabolism in diatoms that cooccur regularly in an estuary on the east coast of the United States (Narragansett Bay). Expression of known N and P metabolic pathways varied between diatoms, indicating apparent differences in resource utilization capacity that may prevent direct competition. Nutrient amendment incubations skewed N/P ratios, elucidating nutrient-responsive patterns of expression and facilitating a quantitative comparison between diatoms. The resource-responsive (RR) gene sets deviated in composition from the metabolic profile of the organism, being enriched in genes associated with N and P metabolism. Expression of the RR gene set varied over time and differed significantly between diatoms, resulting in opposite transcriptional responses to the same environment. Apparent differences in metabolic capacity and the expression of that capacity in the environment suggest that diatom-specific resource partitioning was occurring in Narragansett Bay. This high-resolution approach highlights the molecular underpinnings of diatom resource utilization and how cooccurring diatoms adjust their cellular physiology to partition their niche space.
多样的海洋浮游植物群落进行着全球一半的初级生产。长期以来，浮游植物的巨大多样性一直困扰着生态学家，因为这些生物在一个各向同性的环境中共同存在，同时竞争相同的基本资源（如无机养分）。资源的差异生态位划分是解释这种“浮游生物悖论”的一种假说，但很难在原位量化和追踪浮游植物代谢的变化。在这里，我们使用定量宏转录组分析来研究在美国东海岸一个河口（纳拉甘西特湾）经常共存的硅藻中氮（N）和磷（P）代谢的途径。已知的N和P代谢途径的表达在不同硅藻之间有所不同，这表明在资源利用能力上存在明显差异，可能会避免直接竞争。营养添加培养使N/P比发生偏差，阐明了营养响应的表达模式，并便于对不同硅藻进行定量比较。资源响应（RR）基因集在组成上与生物体的代谢谱不同，富含与N和P代谢相关的基因。RR基因集的表达随时间变化，并且在不同硅藻之间有显著差异，导致对相同环境产生相反的转录反应。代谢能力以及在环境中这种能力的表达存在明显差异，这表明在纳拉甘西特湾发生了硅藻特异性的资源划分。这种高分辨率方法突出了硅藻资源利用的分子基础，以及共存硅藻如何调整其细胞生理以划分其生态位空间。
