Life and Environmental Sciences and Sierra Nevada Research Institute, University of California, Merced, Merced, CA, USA.
ISME J. 2013 Nov;7(11):2192-205. doi: 10.1038/ismej.2013.96. Epub 2013 Jun 27.
Nitrogen (N) is an essential nutrient in the sea and its distribution is controlled by microorganisms. Within the N cycle, nitrite (NO2(-)) has a central role because its intermediate redox state allows both oxidation and reduction, and so it may be used by several coupled and/or competing microbial processes. In the upper water column and oxygen minimum zone (OMZ) of the eastern tropical North Pacific Ocean (ETNP), we investigated aerobic NO2(-) oxidation, and its relationship to ammonia (NH3) oxidation, using rate measurements, quantification of NO2(-)-oxidizing bacteria via quantitative PCR (QPCR), and pyrosequencing. (15)NO2(-) oxidation rates typically exhibited two subsurface maxima at six stations sampled: one located below the euphotic zone and beneath NH3 oxidation rate maxima, and another within the OMZ. (15)NO2(-) oxidation rates were highest where dissolved oxygen concentrations were <5 μM, where NO2(-) accumulated, and when nitrate (NO3(-)) reductase genes were expressed; they are likely sustained by NO3(-) reduction at these depths. QPCR and pyrosequencing data were strongly correlated (r(2)=0.79), and indicated that Nitrospina bacteria numbered up to 9.25% of bacterial communities. Different Nitrospina groups were distributed across different depth ranges, suggesting significant ecological diversity within Nitrospina as a whole. Across the data set, (15)NO2(-) oxidation rates were decoupled from (15)NH4(+) oxidation rates, but correlated with Nitrospina (r(2)=0.246, P<0.05) and NO2(-) concentrations (r(2)=0.276, P<0.05). Our findings suggest that Nitrospina have a quantitatively important role in NO2(-) oxidation and N cycling in the ETNP, and provide new insight into their ecology and interactions with other N-cycling processes in this biogeochemically important region of the ocean.
氮（N）是海洋中的一种必需营养物质，其分布受微生物控制。在氮循环中，亚硝酸盐（NO2(-)）起着核心作用，因为其中间氧化还原状态允许氧化和还原，因此它可能被几种耦合和/或竞争的微生物过程使用。在东热带北太平洋（ETNP）的上层水柱和缺氧区（OMZ）中，我们使用速率测量、通过定量 PCR（QPCR）定量 NO2(-)氧化细菌和焦磷酸测序来研究好氧 NO2(-)氧化及其与氨（NH3）氧化的关系。在六个采样站中，通常在两个次表层处出现（15）NO2(-)氧化速率的两个次表层最大值：一个位于透光带以下和 NH3 氧化速率最大值以下，另一个位于 OMZ 内。（15）NO2(-)氧化速率在溶解氧浓度<5 μM 的地方最高，在那里 NO2(-)积累，并且硝酸盐（NO3(-)）还原酶基因表达；它们可能在这些深度处由 NO3(-)还原维持。QPCR 和焦磷酸测序数据高度相关（r(2)=0.79），并表明 Nitrospina 细菌数量高达细菌群落的 9.25%。不同的 Nitrospina 群体分布在不同的深度范围内，表明整个 Nitrospina 具有显著的生态多样性。在整个数据集上，（15）NO2(-)氧化速率与（15）NH4(+)氧化速率脱钩，但与 Nitrospina（r(2)=0.246，P<0.05）和 NO2(-)浓度（r(2)=0.276，P<0.05）相关。我们的研究结果表明，Nitrospina 在 ETNP 的 NO2(-)氧化和 N 循环中具有重要的定量作用，并为它们在该海洋生物地球化学重要区域的生态学及其与其他 N 循环过程的相互作用提供了新的见解。
