Different Driving Factors for Potential Activity of Ammonia-Oxidizing Archaea and Bacteria in Coastal Wetlands

Abstract This study aimed to evaluate which environmental factors and genetic groups were important in explaining measured activity of Ammonia-oxidizing archaea (AOA) and bacteria (AOB), which play important roles in global nitrogen cycle, providing a new insight into the mechanism of archaeal and bacterial ammonia oxidation. We sampled 62 soil/sediment samples from coastal wetlands of the Bohai area of China and assessed the abundance of functional genes involved in the nitrogen cycle, soil/sediment characteristics and the potential activity of AOA (PAOA) and AOB (PAOB) using specific inhibitors. At last, we introduced the structure equation model (SEM) to infer direct and indirect effects of variables on potential activities. The results indicated that the change in AOA-amoA gene abundance may be more independent, while AOB-amoA was closely associated with the change in abundance of amx and denitrifier. PAOA was mainly defined by AOA-amoA abundance and partially influenced by the norA gene, suggesting coupling of archaeal ammonia oxidation with nitrite oxidation. PAOB was significantly defined by the abundance of amx and denitrifier, indirectly mediated by AOB-amoA. The activity of AOA seemed to be more independent of other microbial activities, while the activity of AOB varied closely with fluctuations of other microbial species. PAOA was mediated directly by the C/N ratio and indirectly by nitrite concentration and TOC value, while PAOB was mediated directly by ammonium concentration and TOC value and indirectly by C/N ratio. The activity of AOB may be determined by several other functional gene groups and had little correlation with AOB abundance while the activity of AOA was mostly controlled by itself.