Stable-isotope Probing of Methanotrophs and Methylotrophs Offshore Southwestern Taiwan

• Main Authors: Pin-Chen Liu, 劉品辰
• Other Authors: 王珮玲
• Format: Others
• Language: zh-TW
• Published: 2015
• Online Access: http://ndltd.ncl.edu.tw/handle/48221930433533635302

碩士 === 國立臺灣大學 === 海洋研究所 === 103 === Methanotrophs and methylotrophs can utilize methane, methanol or a variety of single carbon compounds as their sole carbon and energy source. They have been found in seawater and play an essential role in carbon cycling, but the details are still less clear. This study investigated methane concentrations in water column above submarine mud volcanoes (MV1, MV2, MV5, MV12) and cold seeps (the Four Way Closure Ridge) offshore southwestern Taiwan and applied cultivation and stable-isotope probing (SIP) to examine the identity of methanotrophys and methylotrophys in these environments. Higher methane concentrations were detected in the bottom water of most submarine mud volcanoes, while MV12 was the most active one during sampling periods. Chemosynthetic communities (shells or mussels) and authigenic minerals are widely observed on the seafloor around the Four Way Closure Ridge, although the methane concentration is low in the bottom water. Because the methane concentration in surface water is closed to background, a certain machanism should be responsible for methane consumption in seawater. Several water samples from MV12 and Four Way Closure Ridge were incubated with additions of normal or 13C-labelled methane or methanol. All incubations with methanol addition showed CO2 increase in headspace, which may infer the growth of methanol oxidizer. CH4 decrease in headspace was only observed in one sample, indicating possible growth of methanotrophs. On the basis of SIP, 13C-DNA was separated from the unlabelled DNA for further examination. The 16S rDNA sequence of 13C-DNA fractions were closely related to the sequence of methylotrophic group and Methylophaga sp. Quantitative real-time PCR assays for the pmoA gene showed highest abundance in 13C-DNA fractions. The pmoA gene of 13C-DNA fractions were closed to that of Type I methanotrophs (similarity of 72-80 %) and the mxaF gene of 13C-DNA fractions was related to that of Type I methanotrophs (similarity > 82 %) and Methylophaga sp. (similarity > 88 %).