Application of T-RFLP analysis to the study of bacterial community structure in the rhizosphere

To analyze the structure of the bacterial communities in the spinach rhizos phere, we used a terminal-restriction fragment length polymorphism (T-RFLP) analysis. The T-RFLP electropherograms revealed several large peaks and sm aller peaks, which were ascribed to various bacterial species composing eac h of the bacterial communities. It is considered that T-RFLP analysis is a convenient method for assessing the microbial diversity or community struct ure in the rhizosphere. Bacterial DNA from colonies on dilution plates and directly extracted bacterial DNA of rhizosphere samples were analyzed by T- RFLP in order to determine whether agar-grown colonies are representative o f the dominant bacterial groups in the rhizosphere. The T-RFLP patterns obt ained by using bacterial colonies from dilution plates as the source of tar get DNA were different from those found with the direct DNA extracts. The r esults indicated that many bacterial groups grown on agar media selective f or the rhizosphere are not likely to be dominant in the rhizosphere.