|Reardon, Catherine - Kate|
|MAYNARD-JOHNSON, JODI - University Of Idaho|
|BROOKS, ERIN - University Of Idaho|
|KAHL, KENDALL - University Of Idaho|
|NORBY, JESSICA - University Of Idaho|
Submitted to: Frontiers in Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/29/2019
Publication Date: 6/26/2019
Citation: Schlatter, D.C., Reardon, C.L., Maynard-Johnson, J.L., Brooks, E., Kahl, K.B., Norby, J., Huggins, D.R., Paulitz, T.C. 2019. Mining the drilosphere: bacterial communities and denitrifier abundance in a no-till wheat cropping system. Frontiers in Microbiology. 10:1339. https://doi.org/10.3389/fmicb.2019.01339.
Interpretive Summary: Earthworms play an important role in no-till wheat cropping system. In this study, we looked at the bacterial communities in intact worm channels (drilosphere) of Lumbricus terrestris) from soil cores taken from three landscape locations (top, middle and bottom slope positions) in a long-term no-till wheat field in eastern WA. We found unique communities in the worm channels compared to the bulk soil. We also quantified genes involved in denitrification from the soil, this is a process that leads to loss of nitrogen as nitrous oxide and other gases.
Technical Abstract: Earthworms play an important role in no-till wheat cropping systems, by redistributing crop residue to lower soil profiles, providing channels for root growth, increasing water infiltration, enhancing soil quality and organic matter, and stimulating nitrogen cycling. Earthworms may also affect microbial communities. 50 cm-deep cores were extracted from 3 landscape locations (top, middle and bottom slope positions) in a long-term no-till wheat field in eastern WA. Soil was sampled from multiple earthworm (Lumbricus terrestris) channels (drilosphere) and adjacent bulk soil at the bottom of the cores. Bacterial communities were characterized from both channel and bulk soil with Illumina sequencing of 16S rRNA genes and denitrification genes (nirK, nirS and nosZ) were quantified with real time PCR. Bacterial communities were structured primarily by the landscape position of the soil core followed by source (bulk versus channel soil), with a significant interaction between core position and source. The families AKIW874, Chitinophagaceae, and Comamonadaceae and the genera Amycolatopsis, Caulobacter, Nocardioides, and Variovorax were more abundant in the channels compared to the bulk soil. Most of the individual bacterial taxa enriched in earthworm channel versus bulk soil were members of Actinobacteria, including Micrococcales, Gaiellaceae, Solirubrobacterales, and Mycobacterium. Bacterial richness and diversity was highest in the bottom slope location, with diversity higher in the channels compared to the bulk soil. nirK and nirS were more abundant in the bottom slope location, but there was no consistent trend between bulk and channel soil. There were significant correlations between the abundance of nirK and nirS and taxa in Proteobacteria, Acidobacteria, Actinobacteria, Verrucomicrobia, and Chloroflexi, suggesting a broad diversity of denitrifying bacteria. Earthworm channels have unique bacterial communities, but they are highly dependent on location in a highly variable landscape.