PAGE ANALYSIS OF THE HETERODUPLEXES FORMED BETWEEN PCR-AMPLIFIED 16S RIBOSOMAL-RNA GENES - ESTIMATION OF SEQUENCE SIMILARITY AND RDNA COMPLEXITY

Analysis of the 16S rRNA genes retrieved directly from different envir onments has proven to be a powerful tool that has greatly expanded our knowledge of microbial diversity and phylogeny. It is shown here that sequence similarity between 80 and 100% among 16S rRNAs can be estima ted by the electrophoretic migration of their heteroduplexes. This was measured by hybridization and electrophoresis in polyacrylamide gels of the product obtained after PCR amplification of almost the entire 1 6S rRNA gene from different bacterial species. These heteroduplexes we re also observed after amplification of samples containing DNA from tw o or more bacterial species and a procedure was applied to identify re liably heteroduplexes among the amplification products. The electropho retic migration of the heteroduplexes observed after PCR was used to d etect the presence of 16S rRNAs with different sequences in DNA extrac ted from both a mixture of two bacterial species and samples containin g a natural bacterial community.