Abundance and community structure of sphingomonads in leaf residues and nearby bulk soil

We examined the abundance and community structure of sphingomonads in the decaying leaf residues of eight plant species as well as the nearby soil, by 16S rRNA gene-based real-time PCR and denaturing gradient gel electrophoresis. In the leaf residues, the sphingomonads generally accumulated to high levels, comprising approximately 15% of the total bacteria, and formed a community structure related to sampling locations. At least within the time period studied, their abundance in leaf residues changed, but their community structure was basically maintained. In soil, sphingomonads made up only 1.7% of total bacteria on average. The community structure of sphingomonads differed between the leaf residues and bulk soil, among plant plots, and among samples collected at different times. The results show that particular sphingomonad populations accumulate in leaf residues compared to the surrounding bulk soil under field conditions.