Archaeal community structures associated with fine root systems of Cryptomeria japonica (Cupressaceae) in central Japan

Abstract

ABSTRACT Archaea live in extreme environments and have been found in non-extreme environments in recent years. Although most studies have focused on the nitrification function of archaea in forest soils, few studies have focused on how archaea in rhizospheres are involved in nutrient absorption. To elucidate the archaeal community pattern inhabiting the fine roots of trees, we examined the taxonomic identity and community structure of archaea in Japanese cedars (Cryptomeria japonica). Root samples were collected from six C. japonica plantations in central Japan. DNA was separately extracted from the first- and third-order roots, and archaeal taxa were determined by the cloning method focusing on 16S rDNA. As a result, 90% of the sequences were classified as in the phylum Thaumarchaeota, with 1.1b and 1.1c groups in the phylum accounting for 65% and 25%, respectively. Archaeal community structures were significantly correlated with soil pH, but neither the root orders nor the plantation sites showed significant clustering. These results suggest that Thaumarchaeota is the dominant archaeal group in the fine roots of C. japonica, and community structures are affected by a proximate chemical factor of soil acidity.