N-175. The Impact of Arbuscular Mycorrhizal Fungi on Bacterial and Archaeal Communities in Decomposing Root Litter

E. Nuccio1, A. Hodge2, M. Firestone1;
1Univ. of California, Berkeley, CA, 2Univ. of York, York, UNITED KINGDOM.

Arbuscular mycorrhizal fungi (AMF) colonize the roots of most plants, however little is known about how AMF affect soil carbon cycling. Previous research has shown that the presence of AMF can accelerate decomposition of plant detritus, even though AMF themselves do not have saprotrophic capabilities. We hypothesized that AMF alter microbial communities involved in decomposing plant material. To test this hypothesis, chopped Plantago lanceolata roots were placed in soil separated from live P. lanceolata roots inoculated with Glomus hoi in sterile sand terragreen. The two chambers were separated by 20- or 0.45-micron mesh to either include or exclude AMF. The soil containing the decomposing root debris was destructively sampled after 40 days when microscopic observations confirmed that AMF had fully colonized the decomposing root debris. The archaeal and bacterial communities present in the root debris soil were analyzed using PhyloChip high-density microarrays. Universal bacterial and archaeal 16S markers were quantified by qPCR to determine if changes in community composition were accompanied by changes in 16S copy number. Ordination (NMS) of the microarray intensity values shows that the communities cluster based on the presence or absence of AMF, and that the separation was statistically significant using MRPP. Quantitative PCR detected no significant response in bacterial 16S copy number in the presence of AMF; archaeal 16S copy numbers were slightly but significantly higher in the presence of AMF. These results indicate that the presence of AMF does modify the microbial community, and that high-density microarray analysis can detect small population changes in a complex soil microbial community.