Environmental Engineering Reference
In-Depth Information
Growth of LB400 (pRO41) and control
LB400 (pRT1) on 2-CB (1 mM)
0.35
1.5
OD, pRO41
OD, pRT1
Cl
−
, pRO41
Cl
−
, pRT1
2CBA, pRO41
2CBA, pRT1
0.30
0.25
1.0
0.20
0.15
0.10
0.5
0.05
0.00
0.0
0
20
40
60
80
Time, hours
Growth of LB400 (pRO41) and control
LB400 (pRT1) on 2-2
-CB (1 mM)
′
0.25
3.0
OD, pRO41
OD, pRT1
Cl
−
, pRO41
Cl
−
, pRT1
2CBA, pRO41
2CBA, pRT1
2.5
0.20
2.0
0.15
1.5
0.10
1.0
0.05
0.5
0.00
0.0
0
20
40
60
80
100
120
140
Time, hours
Figure 6.16
Growth of LB400(pRO41::
ohb
) and LB400 on ortho-PCBs.
measured, indicating complete mineralization of 2,2′-CB. Therefore, simul-
taneous expression of the two ortho-dehalogenating dioxygenases, BDO and
ISP-OHB, resulted in complete mineralization of 2,2′-CB. In addition, LB400
grew on 3-CBA due to the indigenous chlorocatechol pathway. Conse-
quently, LB400(pRO41) efficiently grew on 2,3- and 2,5-dichloribenzoates
and on dichlorobenzoates 2,4- and 2,6-dCBAs, although the latter two are
poor growth substrates.
We showed that efficiency of degradation of 2-CBP and 2,2′-CBP by
recombinant LB400(pRO41) was dependent on preparation of inoculum.
Whereas complete mineralization of 2-CBP was not affected by whether the
inoculum was grown on BP or 2-CBA, a dramatic difference was found with
a higher-chlorinated 2,2′-CB. In the latter case, complete mineralization was
achieved only with inoculum grown on 2-CBA, whereas only partial degra-
dation was observed with BP-grown inoculum. Indeed, BP-initiated culture
LB400(pRO41) behaved similarly to control strain LB400(pRT1), except that
no 2-CBA accumulated in the former, indicating that the incomplete miner-
alization could not be attributed to plasmid instability (loss of the
ohb
genes).
