Aerobic and Anaerobic Ammonia-Oxidizing Microorganisms in Low-Temperature Hydrothermal Fe-Si-rich Precipitates of the Southwestern Pacific Ocean

Abstract

Fe-Si-rich hydrothermal precipitates are distributed widely in low-temperature diffusing hydrothermal fields. Due to the significant contribution of Fe-oxidizing bacteria (FeOB) to the formation of this type of hydrothermal precipitates, previous studies focus mostly on investigating FeOB-related microbial populations, albeit these precipitates actually accommodate abundant other microbial communities, particularly those involved in marine nitrogen cycle. In this study, we investigated the composition, diversity, and abundance of aerobic and anaerobic ammonia-oxidizing microorganisms dwelling in low-temperature Fe-Si-rich hydrothermal precipitates of the Lau Integrated Study Site based on ammonia monooxygenase (amoA) gene and 16S rRNA gene. Phylogenetic analysis revealed the common presence of ammonia-oxidizing archaea (AOA), Nitrosospira-like ammonia-oxidizing bacteria (AOB) and anaerobic ammonium-oxidizing anammox (bacteria) in the Fe-Si-rich hydrothermal precipitates. Quantitative PCR analysis showed that AOA dominated the whole microbial community and the abundance of archaeal amoA gene was 2–3 orders of magnitude higher than that of AOB and anammox bacteria. Result of glycerol dialkyl glycerol tetraether analysis confirmed the presence and abundance of AOA. Our results suggest that microbial ammonia oxidations, especially archaeal aerobic ammonia oxidation, are prevalent and pivotal processes in low-temperature diffusing hydrothermal fields.

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Keywords:

• ammonia oxidation
• amoA gene
• anammox
• Fe-Si-rich hydrothermal precipitates
• glycerol dialkyl glycerol tetraether

Acknowledgments

This work was financially supported by the National Basic Research Program of China (973 Program, No. 2012CB417300), National Natural Science Foundation of China (NSFC, No. 41002122 and 41240039) and the Fundamental Research Funds for the Central Universities. We thank all crew members of R/V DaYang YiHao for retrieving the samples studied. The LC-MS analysis was performed at the State Key Laboratory of Marine Geology of Tongji University.