Few traditional methods are applicable in study of the microbial community in the field of microbial ecology in recent years, since most of them rely on the microscope and cultivation of bacteria on laboratory media, and it had been proved that only about 1% of total number of actively respiring bacterial cells can be cultured on laboratory media. In addition, less than 1% bacterial species have been isolated and characterized from soil samples. As a new DNA fingerprinting technique, denaturing gradient gel...