Capacity evaluation of different media for isolating bacteria populations from the rhizospere of tomato plants with DGGE
利用DGGE评价不同培养基回收番茄根际细菌类群的能力

Bacteria from the rhizosphere of tomato plants were cultured on nutrient broth, YG, soil extract and root exudate media. The capabilities of these 4 media for recovering the bacterium communities were evaluated with denaturing gradient gel electrophoresis (DGGE) technique. Results showed that there were certain differences in the obtained bacterial communities when different media and culture tempitures were applied. Numbers of CFU on solid media indicated that the YG agar medium incubated at 20 degrees C could recover more populations than the high-nutrient-concentration Nutrient agar medium; while the root exudate based medium recovered the highest numbers of bacteria from the rhizosphere of tomato plants. 16S rDNA fragments amplified by PCR from different media and rhizosphere soil bacterium DNA were analyzed with DGGE. The DGGE fingerprints showed that there was a discrepancy between bacterial populations observed by cultivation techniques and molecular retrieval. The rhizosphere pattern consisted of more strong bands than the media. The DGGE patterns of the 4 different media incubated at 28 degrees C showed a relatively high level of similarity. In contrast, those of the 4 media incubated at 20 degrees C were significantly different from each other. Shannon-Wiener index (H), species richness (S), Cs values and Cluster dendrogram analysis of different samples revealed that the YG agar medium and the root exudate based medium recovered the highest proportion of predominant populations from the rhizosphere. In the study a new strategy has been proposed for evaluating the capacity of different media in terms of recovering the predominant populations.