6c CAACGCGARGAACCTTACC 966–984

The advantages of using SSU rRNA for community fingerprinting are many: (i) This gene is found in all cellular life forms. (ii) It is a highly conserved gene, serving to a large degree as a reliable molecular chronometer. (iii) It is seldom transferred horizontally. (iv) It possesses both conserved and variable regions, so that the conserved regions can be targeted by polymerase chain reaction (PCR) primers and the variable ones be used as identifying markers. A handful of other genes, such as the large subunit (LSU) rRNA share these properties, but the length of ~1,500 bp of the bacterial SSU rRNA made it amenable to early molecular techniques, and the impressive body of knowledge that has since accumulated on the basis of this gene makes a switch to other markers very impractical, except in certain sub-fields such as mycology, where ITS and LSU are widely used.