Microbiological assessment of circulation mud fluids during the first operation of riser drilling by the deep-earth research vessel Chikyu
Microbiological assessment of circulation mud fluids during the first operation of riser drilling by the deep-earth research vessel Chikyu
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DOI：
10.1080/01490450802258154
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发表时间：
2008-01-01
影响因子：
2.3
通讯作者：
Inagaki, Fumio
中科院分区：
文献类型：
--
作者：
Masui, Noriaki;Morono, Yuki;Inagaki, Fumio
质量保证和控制 (QA/QC) 对于科学钻探具有重要意义，以便准确表征深部海底取芯材料的物理、地球化学和生物特性。为了探索海底深处的生命及其生物圈，钻芯中微生物污染的识别和控制对于高灵敏度分子分析和培养至关重要，特别是对于低生物量和/或极其恶劣的深层环境的评估。在这里，我们报告了新建的深地地球研究船 Chikyu 进行首次隔水管钻井作业前后循环泥浆流体的一些微生物特征。在 2006 年 Chikyu 试航考察 CK06-06 期间，我们使用立管系统在海底以下 547 至 647 米处钻探到日本下北半岛近海的沉积物中。培养实验表明，预循环泥浆中未见微生物生长，而后循环泥浆中每1 ml可观察到4 105个菌落；所有培养的细菌分离株均被发现为盐单胞菌。使用不依赖于培养物的分子分析，在预循环泥浆液中主要检测到用于工业生产泥浆增粘剂黄原胶的黄单胞菌属的16S rRNA基因序列，而盐单胞菌序列始终在由后循环泥浆液构建的克隆库中占主导地位。古菌 16S rRNA 基因仅从后循环泥浆中扩增；这些古菌克隆序列属于海洋泉古菌群 I (MGI)、海洋广古菌群 II (MGII)、杂泉古菌群 (MCG)、南非金矿广古菌群 (SAGMEG)、土壤群和风热甲烷球菌。这些结果表明，盐单胞菌在循环泥浆液槽中被污染和生长，其他深层海底微生物成分，特别是深层地下古细菌，也被混合到后循环泥浆液中。
Quality assurance and control (QA/QC) is significant for the scientific drilling in order to accurately characterize physical, geochemical, and biological properties in the cored deep subseafloor materials. To explore the deep subseafloor life and its biosphere, identification and control of microbial contamination in drilling cores is critical for highly sensitive molecular analyses as well as cultivations, especially for the evaluation of low biomass and/or extremely harsh deep environments. Here we report some microbiological characteristics of circulation mud fluids before and after the first riser drilling operation by the newly constructed deep-earth research vessel Chikyu. During the Chikyu shakedown expedition CK06-06 in 2006, we used the riser system for drilling 547 to 647 meter below the seafloor into the sediments offshore the Shimokita Peninsula of Japan. Cultivation experiments showed that no microbial growth was observed in the precirculation mud fluid, while 4 105 colonies per 1 ml were observed in the postcirculation mud fluid; all cultured bacterial isolates were found to be Halomonas. Using culture-independent molecular analysis, 16S rRNA gene sequences of Xanthomonas, which is used for industrial production of the mud fluid viscosifier xanthan gum, were predominantly detected in the precirculation mud fluid, while Halomonas sequences consistently dominated the clone library constructed from the postcirculation mud fluid. Archaeal 16S rRNA genes were amplified only from the postcirculation mud fluid; these archaeal clone sequences were affiliated to the Marine Crenarchaeota Group I (MGI), Marine Euryarchaeota Group II (MGII), Miscellaneous Crenarchaeotic Group (MCG), South African Gold Mine Euryarchaeotic Group (SAGMEG), Soil Group, and Methanococcus aeolicus. These results suggest that Halomonas contaminated and grew in the tank of circulation mud fluids, and other indigenous deep subseafloor microbial components, especially deep subsurface archaea, were also mixed into the post-circulation mud fluid.