ABSTRACT
Until the 1980s, the determination of microbial community structure and the identification of microorganisms in environmental samples depended on culture-based studies. These can be both time-consuming and cumbersome and were already known to be selective, as only a small part of a microbial community is accessed (1). Two major discoveries have revolutionized microbial ecology and have permitted culture-independent characterization of microbial communities: the recognition that phylogenetic relationships between microorganisms can be inferred from molecular sequences (2) and the ability to selectively amplify minute amounts of nucleic acids extracted from environmental samples by the polymerase chain reaction [PCR; 3).
