PNNL-13501 - Pacific Northwest National Laboratory

Summary and Conclusions
• The great majority of the ribotypes present in the
rDNA from the microbial community were not found
in the isolates that were cultured, highlighting the
importance of molecular-based analyses for
understanding the integrated soil-plant system.
• Terminal restriction fragment analysis using rRNA
molecules from the microbial community showed
greater differences between management strategies
than use of rDNA molecules.
• Tillage practices affected microbial community
structure while nitrogen level appeared to have little
to no effect.
• The highest order difference in the study was
between rhizosphere and no-plant soils, indicating
that the influence of the wheat root overrides the soil
management practices that were examined.
• Terminal restriction fragment analysis is a rapid and
robust means of fingerprinting the set of dominant
and largely uncultured microorganisms in the
microbial community. Proper editing and computer
analysis of the electropherogram profiles was by far
the most time-consuming portion of the project. This
was in part due to a learning curve associated with
the software. However, even in the future, editing
and computer analysis of the profiles will remain
more time-consuming than RNA extraction/
purification or obtaining the terminal restriction
fragment profile.
Biosciences and Biotechnology 99