Distribution of archaeal and bacterial tetraether membrane lipids in rhizosphere-root systems in soils and their implication for paleoclimate assessment

Abstract

Branched and isoprenoidal glycerol dialkyl glycerol tetraethers (GDGT) are abundant in soils, but little is known about the presence of branched GDGT in rhizosphere-root systems versus bulk soils, and implications of these for GDGT-based climate reconstruction. Here we investigate the archaeal and bacterial communities by studying both core and intact polar GDGT in rhizosphere-root systems of Cinnamomum camphora (Linn) Presl. As well as in litter and some bulk forest soils in Wuhan in central China. The higher abundance of core and intact polar branched GDGT in the rhizoplanes than their associated roots, rhizospheres and bulk soil argue for the presence of heterotrophic branched GDGT-producing bacteria living in direct association with the root surface and feeding on root exudates. In addition, this study showed that the application of the revised calibration (Peterse et al., 2012) produced temperatures closer to the mean annual air temperature than the original global soil calibration (Weijers et al., 2007b). It seems from the similarity of the MBT′ (revised index of methylation of branched tetraethers) and the estimated temperature values that the branched GDGT-producing bacteria in all samples belong to the same community in the studied forest soil.