On the molecular taxonomy of Trypanosoma cruzi using riboprinting

In order to investigate the molecular taxonomy within Trypanosoma cruzi, the ribosomal small subunit (18S) gene was amplified by polymerase chain reaction (PCR) from a selection of 21 stocks and 3 outgroup taxa. Amplification products were digested with 10 restriction enzymes; restriction fragments were separated by polyacrylamide gel electrophoresis and profiles were visualized by silver staining. Upon analysis of such riboprint profiles, an estimate of pairwise phenetic distance between stocks of T. cruzi was calculated. Upon principal coordinate analysis of this data matrix, a tendency towards a bi-polar grouping of stocks was observed. These 2 groups were predominantly either zymodeme 1 stocks or zymodeme 2 stocks. The position of zymodeme 3 stocks remained intermediate between the 2 groups but did not form a coherent group by themselves. It would therefore appear premature to warrant division of T. cruzi into 2 discrete taxa or subspecies until the relationships of further zymodeme 3 stocks are elucidated.