Fixed bacterial cells were used in DPCR analysis.
Immediately before DPCR analysis, the cell pellets were
thawed, resuspended in 50 ll and decimally diluted in
double distilled water. Each dilution was used as a template
for PCR. For quantitative analysis, 50 ll of a cell suspension
containing 107 cells was serially diluted to extinction in five
replicate series. A negative control with no template was
included in each dilution series. The final volume of each
PCR was 100 ll. We have previously described the calculation
of most probable number-DPCR (MPN-DPCR)
(Fode-Vaughan et al. 2001). The sensitivity of DPCR with
each primer pair was evaluated by comparing the number of
cells added to the DPCR reactions determined by direct
count and the cell number estimated by MPN-DPCR.