N2 fixation by unicellular bacterioplankton from the Atlantic and Pacific oceans:: Phylogeny and in situ rates
N2 fixation by unicellular bacterioplankton from the Atlantic and Pacific oceans:: Phylogeny and in situ rates
复制标题
DOI：
10.1128/aem.70.2.765-770.2004
复制
发表时间：
2004-02-01
影响因子：
4.4
通讯作者：
Capone, DG
中科院分区：
文献类型：
--
作者：
Falcón, LI;Carpenter, EJ;Capone, DG
N-2 固定变形菌（α 和 γ）和单细胞蓝藻在热带北大西洋和太平洋中都很常见。在近地表水域中，变形菌 nifH 转录本在夜间和白天均存在，而单细胞蓝藻 nifH 转录本仅在夜间存在，这表明单细胞蓝藻的 N-2 固定和光合作用是分离的。对蓝藻 16S 核糖体 DNA (rDNA) 的保守区域进行测序后，确定了来自两个海洋的单细胞蓝藻之间的系统发育关系，结果表明，无论起源于哪个海洋，它们都聚集在一起。然而，对来自两个海洋的单细胞蓝藻的 nifH 转录本进行测序表明，它们分别聚集在一起。这表明来自北大西洋热带地区和北太平洋亚热带地区的单细胞蓝藻具有共同的祖先（16S rDNA），并且潜在的单细胞 N-2 固定剂已经出现分歧（nifH）。根据乙炔还原和 N-15(2) 方案原位测定了两个海洋单细胞浮游细菌（包括小型蓝藻）的 N-2 固定率。结果表明，浮游细菌的固定率几乎与固着N-2的海洋蓝藻Trichodesmium spp的固定率一样高。在热带北大西洋，但在亚热带北太平洋，这一比率要低得多。
N-2-fixing proteobacteria (alpha and gamma) and unicellular cyanobacteria are common in both the tropical North Atlantic and Pacific oceans. In near-surface waters proteobacterial nifH transcripts were present during both night and day while unicellular cyanobacterial nifH transcripts were present during the nighttime only, suggesting separation of N-2 fixation and photosynthesis by unicellular cyanobacteria. Phylogenetic relationships among unicellular cyanobacteria from both oceans were determined after sequencing of a conserved region of 16S ribosomal DNA (rDNA) of cyanobacteria, and results showed that they clustered together, regardless of the ocean of origin. However, sequencing of nifH transcripts of unicellular cyanobacteria from both oceans showed that they clustered separately. This suggests that unicellular cyanobacteria from the tropical North Atlantic and subtropical North Pacific share a common ancestry (16S rDNA) and that potential unicellular N-2 fixers have diverged (nifH). N-2 fixation rates for unicellular bacterioplankton (including small cyanobacteria) from both oceans were determined in situ according to the acetylene reduction and N-15(2) protocols. The results showed that rates of fixation by bacterioplankton can be almost as high as those of fixation by the colonial N-2-fixing marine cyanobacteria Trichodesmium spp. in the tropical North Atlantic but that rates are much lower in the subtropical North Pacific.