Patterns of potential C source utilization by rhizosphere communities

Patterns of potential C source utilization by microbial communities were tested as a means for differentiating among and within rhizosphere samples of different crops. Utilization of 95 separate sole C sources was determined by inoculating microbial suspensions into BIOLOG plates and quantifying color production from a redox-sensitive dye. Suspensions were produced by shaking excised root samples from wheat, white potato, soybean and sweetpotato grown in hydroponic culture within controlled environmental growth chambers. Distinctive patterns of C source utilization were apparent for each crop type, and the differences among crops were consistent for experiments repeated over 2 years. A temporal shift in C source utilization related to plant development state was observed in soybean. Results indicate that this rapid method is effective for detecting plant dependent differences in rhizosphere communities, and changes in response to plant developmental state.