Insights into the role of plant on ammonia-oxidizing bacteria and archaea in the mangrove ecosystem
The aim of this study was to elucidate the impact of plant on the activity, abundance, and the community composition of the ammonia oxidizers, including both ammonia-oxidizing archaea (AOA) and bacteria (AOB). Moreover, the relationship between AOA and AOB in mangrove sediment was also analyzed.
Materials and methods
Sediment used for microcosm experiments was collected in the mangrove wetland. The native plant species Kandelia obovata and invasive species Spartina alterniflora were selected. Nitrifying activity was determined by assaying the potential nitrification rate (PNR). Abundances of gene and transcript were measured via real-time quantitative PCR (qPCR). Terminal restriction fragment length polymorphism (T-RFLP) was used to analyze the nitrifier community structures. Clone libraries were constructed for further phylogenetic analysis.
Results and discussion
PNR and abundances of both AOA and AOB were greatly enhanced in the vegetated sediments. S. alterniflora showed a greater promoting effect on nitrification activity, indicating the potential of exotic invasion on perturbing the nitrogen balance. Abundance of AOB transcript was hundreds of times higher than that of AOA. Moreover, ammonia-oxidizing communities were distinctly grouped responding to vegetation with two plant species. Along with direct impact of plants, these variations are as well related to the different sediment properties. Phylogenetic analysis revealed that both AOA and AOB communities formed apparent clusters. The latter contained two Nitrosomonas and Nitrosospira clusters. The Nitrosomonas genus is predominant over Nitrosospira genus, which might be due to the better adaption of Nitrosomonas to the flooded habitats in sediments.
Wetland plants were found to influence the activity, abundance, and community structure of ammonia oxidizers. Moreover, AOB is suggested to be more significant than AOA in nitrogen cycling in mangrove wetlands.
KeywordsAmmonia oxidation Ammonia-oxidizing archaea (AOA) Ammonia-oxidizing bacteria (AOB) Mangrove Plant
This study was financially supported by the Strategic Priority Research Program of Chinese Academy of Sciences (XDB15020302, XDB15020402), the Natural Science Foundation of China (31270153, 41376119), and the International Science & Technology Cooperation Program of China (2011DFB91710). We would like to thank Prof. Yong-guan Zhu from the Institute of Urban Environment, Chinese Academy of Sciences for valuable suggestions on the earlier version of this manuscript.
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