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Abstract:
In this study, we investigated the impact of soil pH on the diversity and abundance of archaeal ammonia oxidizers
in 27 different forest soils across Germany. DNAwas extracted
from topsoil samples, the amoA gene, encoding ammonia
monooxygenase, was amplified; and the amplicons were sequenced
using a 454-based pyrosequencing approach. As expected, the ratio of archaeal (AOA) to bacterial (AOB) ammonia
oxidizers’ amoA genes increased sharply with decreasing
soil pH. The diversity of AOA differed significantly between
sites with ultra-acidic soil pH (<3.5) and sites with higher pH
values. The major OTUs from soil samples with low pH could
be detected at each site with a soil pH <3.5 but not at sites with
pH >4.5, regardless of geographic position and vegetation.
These OTUs could be related to the Nitrosotalea group 1.1
and the Nitrososphaera subcluster 7.2, respectively, and showed
significant similarities to OTUs described from other acidic
environments. Conversely, none of the major OTUs typical of
siteswith a soil pH >4.6 could be found in the ultra- and extreme
acidic soils. Based on a comparison with the amoA gene sequence
data from a previous study performed on agricultural
soils, we could clearly show that the development of AOA
communities in soils with ultra-acidic pH (<3.5) is mainly
triggered by soil pH and is not influenced significantly by the
type of land use, the soil type, or the geographic position of the
site, which was observed for sites with acido-neutral soil pH.
