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Title: Assessing short-term responses of prokaryotic communities in bulk and rhizosphere shils to tall fescue endophyte infection

Author
item Jenkins, Michael
item Franzluebbers, Alan
item Humayoun, Shaheen

Submitted to: American Society for Microbiology Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 3/17/2006
Publication Date: 11/7/2006
Citation: Jenkins, M., Franzluebbers, A.J., Humayoun, S.B. 2006. Assessing prokaryotic communities in bulk and rhizosphere soils of endophyte-infected and endophyte-free tall fescue with fluorescence in situ hybridization [abstract]. American Society for Microbiology Annual Meeting, May 21-25, 2006, Orlando, Florida. 289:309-320.

Interpretive Summary:

Technical Abstract: Background: Tall fescue (Festuca arundinacea Schreb) is a forage grass of world-wide importance. It has a natural association with an endophytic fungus (Neotyphodium coenophialum). In contrast to endophyte-free (E-) tall fescue, endophyte-infected (E+) tall fescue pastures have been shown to enhance soil carbon sequestration. A hypothetical mechanism that may account for the enhanced carbon sequestration is that the E+ tall fescue affects the soil microbial community or components of it that are involved in organic carbon turnover. Methods: A 60-week mesocosm study with a factorial arrangement of soil type (loamy sand and clay loam) and E+ and E- tall fescue was conducted to determine if the soil microbial communities were affected by the presence of the endophyte. Bulk and rhizosphere soil samples were fixed in paraformaldehyde, and homogenized in 0.1% pyrophosphate by mild ultrasonic treatment before being stained with 4’,6-amidino-2-phenylindole (DAPI) for total direct microbial counts, and with a combination of one of a domain or subdivision fluorescent oligonucleotide probe and DAPI for enumerating Eubacteria, bacterial subdivisions, and Archaea. Results: Results of this study showed that the presence of the endophyte significantly decreased the density of the archaeal, and high G+C gram-positive bacterial communities of the bulk clay loam, and delta-proteobacterial, and Planctomycetes communities of the rhizosphere loamy sand. Conclusions: In the long-term, decreases in these microbial communities could account for a decrease in soil organic carbon mineralization. Our results indicated that an E+ tall fescue-soil microbial community interaction may indeed be associated with enhanced soil carbon sequestration.