recovery (data not shown). Signi
fi
cant time savings can be achieved by
chaining eight sets of two microplates in different steps of the protocol,
using multichannel repetition pipettes and by storing strain collections
in microplates. DNA from 16 microwell plates (1536 yeast isolates) can
be obtained in one working day, which is an eight-fold increase com-
pared to the original method (
Lopez et al., 2001
). As shown in
Fig. 2
,
the average DNA concentrations of quadruplicate extractions from 12
S. cerevisiae
strains and 12 other non-
Saccharomyces
species grown in
microplates were 20 ng
μ
L
−
1
(ranging between 20 and 40 ng
μ
L
−
1
)
and 50 ng
μ
L
−
1
(ranging between 10 and 140 ng
μ
L
−
1
) respectively,
suitable for PCR-ampli
fi
cation without the need for further dilution.
When higher DNA concentrations are required, the protocol can be
modi
fi
ed by increasing overnight the culture volumes and decreasing
the volume of diluted TE buffer for DNA resuspension. For cells grown
in microtubes, DNA concentration values were inverted, since the aver-
age concentration of
S. cerevisiae
strainswashigher (830 ng
μ
L
−
1
,rang-
ing between 670 and 1110 ng
μ
L
−
1
)comparedtotheremainingyeast
species (430 ng
μ
L
−
1
ranging between 100 and 1010 ng
μ
L
−
1
). Values
obtained for the A260/A280 ratio were in the range of 1.8
–
2.2, indepen-
dent of the extraction scale or species (data not shown). To evaluate
I.
Overnight culture