����������� The effect of earthworm (Lumbricus terrestris) activity on microbial community composition was investigated in a Gilpin silt loam soil (fine-loamy, mixed, semiactive, mesic Typic Hapludults). Fingerprints of bacterial community structure were constructed using PCR amplicons of bacterial 16S rDNA separated by denaturing gradient gel electrophoresis (DGGE).� Culture-dependent (CD-DGGE) and culture-independent (CI-DGGE) approaches were taken to compare untreated soil; soil that contained worms feeding on manure and/or soil; and worm casts. Analysis of similarity (ANOSIM) established that significant differences existed between community fingerprints within individual gels. ANOSIM R values were as follows: R= 0.93 (P<0.001) for CD-DGGE fingerprint; R= 0.89 (P<0.001) for CI-DGGE fingerprint; and R= 0.95 (P<0.001) for a combined CI and CD DGGE fingerprint. Differences in the similarity data were explored using non-metric Multidimensional Scaling (MDS) and UPGMA.�� Ordination plots and cluster analysis separated earthworm casts from soil treatments for both CD-DGGE and CI -DGGE profiles. CD analysis resulted in 73 total bands; 20 were unique to soil treatments while 24 were unique to earthworm casts.� CI analysis resulted in 64 total bands; 17 were unique to soil and 31 unique to earthworm casts.� Community fingerprints obtained from cast materials separated according to the worm's food source. Soils containing both earthworms and manure separated from all other soil treatments.� Differences in community fingerprints between untreated control soil and soil that received only earthworms were not apparent. �The large separation between CD and CI data indicated different bacterial communities were detected by these methods.� Major trends observed above also were evident in separate analyses employing PCR amplification of nirK �for DGGE, and BIOLOG Eco Plates for community level physiological profiles (CLPP). �Data suggest that bacterial communities are modified after ingestion, however resultant changes in the soil bacterial community only occurred when earthworms consumed a soil manure mixture.

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