AOA and AOB communities respond differently to changes of soil pH under long-term fertilization

Archaeal and bacterial ammonia-oxidizers drive the first step of nitrification, ammonia oxidation. Despite their importance, the relative contribution of soil factors influencing the abundance, diversity and community composition of ammonia oxidizing archaea (AOA) and bacteria (AOB) are seldom compared. In this study, the AOA and AOB communities in soils from a long-term fertilization experiment (which formed gradients of pH and nutrients) were measured using 454 pyrosequencing of the amoA gene. Results showed that both AOA and AOB communities were influenced by fertilization practice. Changes of AOA abundance, diversity and community structure were closely correlated with a single factor, soil pH, and the abundance and diversity of AOA were lower under the acidified treatments. By contrast, AOB abundance was higher in the acidified soil than in the control soil while AOB diversity was little impacted by soil acidification, and both the abundance and diversity of AOB were most highly correlated with soil carbon and available phosphorus. These results indicated that AOB diversity seemed more resistant to soil acidification than that of AOA, and also suggested that AOB have greater ecophysiological diversity and broader range of habitats than AOA in this lime concretion black soil, and the potential contribution of AOB to ammonia oxidation in acid environments should not be overlooked.