Diazotrophic bacterioplankton in a coral reef lagoon: phylogeny, diel nitrogenase expression and response to phosphate enrichment
Diazotrophic bacterioplankton in a coral reef lagoon: phylogeny, diel nitrogenase expression and response to phosphate enrichment
复制标题
DOI：
10.1038/ismej.2007.5
复制
发表时间：
2007-05-01
期刊：
影响因子：
11
通讯作者：
Zehr, Jonathan P.
中科院分区：
文献类型：
--
作者：
Hewson, Ian;Moisander, Pia H.;Zehr, Jonathan P.
我们调查固氮浮游细菌组合组成的鹭礁泻湖（大堡礁，澳大利亚）使用文化独立的技术，针对固氮酶基因的nifH片段。在72小时的时间内（即在昼夜以及潮汐周期），以3小时的间隔收集海水。还进行了孵育实验以评估磷酸盐（PO 43-）可用性对nifH表达模式的影响。基于DNA的nifH文库主要包含与来自沉积物、微生物垫和表面相关微生物的nifH最相似的序列，少数序列与典型的开放海洋生物类型聚类。与基因组DNA序列相反，从基因转录本（通过逆转录-聚合酶链反应扩增的mRNA）制备的文库完全是蓝藻，并且包含与在开阔海洋浮游生物中观察到的相似的蓝藻类型。采用定量聚合酶链反应（QPCR）技术对泻湖样品中束毛藻（Trichodesmium）和两种未培养蓝藻（A组和B组）的丰度进行了研究。这些被检测为转录本，但在基因组DNA中未检测到。在几个昼夜循环中，这些基因转录本的丰度表现出变异性。PO 43-富集实验具有比泻湖采样更清晰的昼夜周期基因表达模式，然而PO 43-添加并没有导致相对于对照孵育物增强的转录丰度。研究结果表明，礁泻湖浮游细菌中的固氮菌可能来源于沉积物、珊瑚或海滩岩石表面，随涨潮脱落成为浮游生物。在泻湖浮游细菌中存在典型的开阔海洋浮游细菌型转录物，可能表明它们是珊瑚礁N循环的重要组成部分。
We investigated diazotrophic bacterioplankton assemblage composition in the Heron Reef lagoon ( Great Barrier Reef, Australia) using culture-independent techniques targeting the nifH fragment of the nitrogenase gene. Seawater was collected at 3 h intervals over a period of 72 h (i.e. over diel as well as tidal cycles). An incubation experiment was also conducted to assess the impact of phosphate (PO43-) availability on nifH expression patterns. DNA-based nifH libraries contained primarily sequences that were most similar to nifH from sediment, microbial mat and surface-associated microorganisms, with a few sequences that clustered with typical open ocean phylotypes. In contrast to genomic DNA sequences, libraries prepared from gene transcripts ( mRNA amplified by reverse transcription-polymerase chain reaction) were entirely cyanobacterial and contained phylotypes similar to those observed in open ocean plankton. The abundance of Trichodesmium and two uncultured cyanobacterial phylotypes from previous studies ( group A and group B) were studied by quantitative-polymerase chain reaction in the lagoon samples. These were detected as transcripts, but were not detected in genomic DNA. The gene transcript abundance of these phylotypes demonstrated variability over several diel cycles. The PO43- enrichment experiment had a clearer pattern of gene expression over diel cycles than the lagoon sampling, however PO43- additions did not result in enhanced transcript abundance relative to control incubations. The results suggest that a number of diazotrophs in bacterioplankton of the reef lagoon may originate from sediment, coral or beachrock surfaces, sloughing into plankton with the flooding tide. The presence of typical open ocean phylotype transcripts in lagoon bacterioplankton may indicate that they are an important component of the N cycle of the coral reef.