Abundance of ammonia-oxidizing organisms across a gradient of preserved Brazilian Cerrado

Abstract

The Brazilian cerrado comprises a diverse vegetation gradient with soils of different physicochemical properties. Previous studies have reported that these different physicochemical properties influence the responses of soil microbial properties. However, no study to date has evaluated the responses of ammonia-oxidizing organisms across the gradient of Brazilian cerrado. In this study, we measured the abundance of ammonia-oxidizing bacteria (AOB) and archaea (AOA) across the Cerrado gradient in northeast Brazil. Soil samples were collected in grassland, Cerrado sensu stricto and cerradao. The qPCR was performed using primers 341F/534R and Arch771F/957R for bacterial and archaeal 16S rRNA gene amplification, respectively. The archaeal and bacterial amoA gene amplifications were carried out using primers Arch-amoAF/AR and A189 and amoA-2R′, respectively. The abundance of archaea, AOA, AOB, and AOA/AOB ratio varied according to the sites; while the abundance of bacteria that did not vary between sites. Usually, AOA and AOB were highest in cerradao than grassland. There were significant correlations between physicochemical and microbial properties and the multivariate analysis clearly separated the sites according to physicochemical and microbial properties. Interestingly, all sites were also clearly separated between the dry and rainy seasons, with soil moisture appearing to be one of the dominant factors influencing cluster separation. In conclusion, the different physicochemical properties of the soil found across the gradient influenced the ammonia-oxidizing archaea, while ammonia-oxidizing bacteria was not driven by these properties. © International Society for Tropical Ecology.