Initially, we investigated the technical reproducibility of
T-RFLP patterns. PCR, enzyme digestions and T-RFLP
analysis were performed on three vaginal samples. After
3 weeks, the procedures were repeated using the same
DNA, which had been stored at –20 uC. Comparison of
corresponding T-RFLP patterns demonstrated excellent
reproducibility, confirming the observations of Osborn
et al. (2000). The mean difference between T-RFs was
,1 bp. The peak heights displayed a higher level of variation;
however, this had no impact on species identification
(data not shown).
Differences between observed and predicted T-RF sizes
usually were within –2 to+2 bp of the predicted T-RF size.
However, the differences grew larger for T-RFs .500 bp
(data not shown). This T-RF drift has been reported
previously and appears to be affected by subtle differences
in molecular mass, from either purine content or dye label
(Kaplan & Kitts, 2003). We observed 109 distinct T-RFs
from 50 to 500 bp, which could be attributed to a total of
23 identifiable T-RF patterns. The mean difference between
maximum and minimum values of all T-RFs was 1.29 bp,
demonstrating the very low variability among observed TRF
sizes corresponding to distinct species or phylotypes
from different samples (as a representative example, see
Table 1 for a detailed analysis of MspI-generated T-RFs).
These data suggested that T-RF length variation due to
strain-to-strain differences was negligible and that overall
reproducibility, defined as technical and biological reproducibility
combined, could be regarded as sufficiently high.