Environmental Engineering Reference
In-Depth Information
120
50/50
50/50
8
50/50
100
50/50
50/50
80
7
50/50
60
6
50/50
50/50
40
50/50
50/50
5
50/50
49/50
20
50/50
4
0
0
10
20
30
Time (days)
40
50
60
Figure 6.12
Survival and degradation of 4
-
CB in soil by RHA1(
fcb
). (Redrawn from
Rodrigues et al.,
Environ. Sci. Technol
., 35, 663-668, 2001.)
nonsterile soil concurrent with 4-CB removal but did not grow in the non-
contaminated, nonsterile control soil, the latter in agreement with growth
being 4-CB specific. Most significantly, the growth of the recombinant strain
also occurred in the nonsterile 4-CB-contaminated soil with concurrent 4-CB
removal. This implicated competitiveness of the RHA1 (
fcb
), which are
within the indigenous soil community. The noninoculated soil showed no
removal of PCB, providing further evidence that the inoculated strain was
responsible for PCB degradation. The RHA1 (
fcb
) appeared stable in both
the sterile and nonsterile soils, and in 60 days only one of the 700 colonies
examined did not yield a
fcbB
amplicon when PCR probed with
fcb
gene-spe-
cific primers (Figure 6.12) (Rodrigues et al., 2001). The long-term effect of
carrying exogenous DNA sequences or expression of new pathways on the
fitness of the recombinant strain was not studied (Lenski et al., 1994); how-
ever, the period in which aerobic PCB treatment is needed in the field would
not normally be much longer than 60 days.
