B41F-0490
Who’s on First? Part II: Bacterial and fungal colonization of fresh soil minerals
Thursday, 17 December 2015
Poster Hall (Moscone South)
Thea Whitman1, Rachel Neurath2, Ping Zhang3, Tong Yuan3, Peter K Weber4, Jizhong Zhou3, Jennifer Pett-Ridge5 and Mary K Firestone2, (1)Cornell University, Crop & Soil Sciences, Ithaca, NY, United States, (2)University of California Berkeley, Berkeley, CA, United States, (3)University of Oklahoma Norman Campus, Norman, OK, United States, (4)Lawrence Livermore National Laboratory, Livermore, CA, United States, (5)Lawrence Livermore National Laboratory, Chemical Sciences Division, Livermore, CA, United States
Abstract:
Soil organic matter (SOM) stabilization by soil minerals is an important mechanism influencing soil C cycling. Microbes make up only a few percent of total SOM, but have a disproportionate impact on SOM cycling. Their direct interactions with soil minerals, however, are not well characterized. We studied colonization of fresh minerals by soil microbes in an Avena barbata (wild oat) California grassland soil microcosm. Examining quartz, ferrihydrite, kaolinite, and the heavy fraction of the native soil, we asked: (1) Do different minerals select for different communities, or do random processes drive the colonization of fresh minerals? (2) What factors influence which taxa colonize fresh minerals? After incubating mesh bags (<18 µm) of minerals buried next to actively growing plant roots for 2 months, we used high-throughput sequencing of 16S and ITS2 genes to characterize the microbial communities colonizing the minerals. We found significant differences between the microbial community composition of different minerals and soil for both bacteria and fungi. We found a higher relative abundance of arbuscular mycorrhial fungi with ferrihydrite and quartz, and nanoscale secondary ion mass spectrometry (NanoSIMS) imaging of these minerals suggests that some fungal hyphae are moving C directly from roots to mineral surfaces. The enriched presence of both nematode-associated fungi (Pochonia sp.) and bacteria (Candidatus Xiphinematobacter) in the minerals suggests that these minerals may be a habitat for nematodes. Bacteria of the family Chitinophagaceae and genus Janthinobacterium were significantly enriched on both ferrihydrite and quartz minerals, both of which may interact with colonizing fungi. These findings suggest that: (1) Microbial colonization of fresh minerals is not a fully passive or neutral process. (2) Mineral exploration by plant-associated fungi and soil fauna transport may be factors in determining the initial colonization of minerals and subsequent C protection.
