Monthly distribution of ammonia-oxidizing microbes in a tropical bay
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Monthly distribution of ammonia-oxidizing microbes in a tropical bay§ Tie-Qiang Mao2, Yan-Qun Li2, Hong-Po Dong1*, Wen-Na Yang2, and Li-Jun Hou1 1 State Key Laboratory of Estuarine and Coastal Research, East China Normal University, Shanghai 200062, P. R. China 2 School of Ocean and Meteorology, Guangdong Ocean University, Zhanjiang 524088, P. R. China
(Received Jun 1, 2020 / Revised Sep 28, 2020 / Accepted Sep 28, 2020)
Ammonia oxidation, performed by ammonia-oxidizing archaea (AOA) and bacteria (AOB), plays a critical role in the cycle of nitrogen in the ocean. For now, environmental variables controlling distribution of ammonia-oxidizing microbes are still largely unknown in oceanic environments. In this study, we used real-time quantitative PCR and high-throughput sequencing methods to investigate the abundance and diversity of AOA and AOB from sediment and water in Zhanjiang Bay. Phylogenic analysis revealed that the majority of AOA amoA sequences in water and sediment were affiliated with the genus Nitrosopumilus, whereas the Nitrosotalea cluster was only detected with low abundance in water. Nitrosomonas and Nitrosospira dominated AOB amoA sequences in water and sediment, respectively. The amoA copy numbers of both AOA and AOB varied significantly with month for both sediment and water. When water and sediment temperature dropped to 17– 20°C in December and February, respectively, the copy number of AOB amoA genes increased markedly and was much higher than for AOA amoA genes. Also, AOA abundance in water peaked in December when water temperature was lowest (17–20°C). Stepwise multiple regression analyses revealed that temperature was the most key factor driving monthly changes of AOA or AOB abundance. It is inferred that low water temperature may inhibit growth of phytoplankton and other microbes and so reduce competition for a common substrate, ammonium. Keywords: ammonia-oxidizing microbes, monthly distribution, community structure, tropical bay Introduction Ammonia oxidation is the rate-limiting step in the nitrification process and plays a pivotal role in the global nitrogen cycle. Ammonia oxidation is traditionally performed by ammonia-oxidizing bacteria (AOB) or ammonia-oxidizing *For correspondence. E-mail: [email protected]; Tel.: +8602154836003 § Supplemental material for this article may be found at http://www.springerlink.com/content/120956. Copyright ⓒ 2021, The Microbiological Society of Korea
archaea (AOA) (Purkhold et al., 2000; Könneke et al., 2005). Recently, it is found that this process is also catalzyed by comammox bacteria that convert ammonia to nitrate directly (Daims et al., 2015; van Kessel et al., 2015). The amoA gene in ammonia-oxidizing microbes has been extensively used as a marker molecule for investigating AOA or AOB community structure and abundance, revealing that AOA and AOB are widely distributed in various environments (Purkhold et al., 2000; Francis et al., 2005; Jiang et al., 2009; Hou et al., 2013; Luo et al., 2015). The distr
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