Biomedical Engineering Reference
In-Depth Information
transport chain linkage occurs at a level above cytochrome b. Alternatively, electron transfer
may be achieved through a non-respiratory electron transport chain.
9.5.4 An Overall Model for CT Transformation
by Pseudomonas stutzeri KC
Figure 9.6 illustrates an overall model for PDTC synthesis, activation/regeneration, and
sustained CT transformation. Requirements are induction of the fur response by the establish-
ment of iron-limiting conditions, presence of actively respiring cells and membrane-linked
regeneration of PDTC activity.
9.6 BIOAUGMENTATION WITH P. STUTZERI KC:
TRANSPORT, GROWTH AND COMPETITION
Bioaugmentation with P. stutzeri KC is a three-step process involving: (1) preparation of the
treatment zone for the introduction of strain KC; (2) growth of a viable inoculum and injection
of strain KC into the treatment zone; and (3) intermittent addition of chemicals to the treatment
zone to maintain strain KC concentrations and to induce genes that regulate production and
secretion of PDTC.
Because P. stutzeri KC does not obtain energy from CT dechlorination (i.e., the reaction is
cometabolic), strategies are needed to ensure its growth and survival over the time period
3
Activation of
fur
Decreased
availability
of Fe
2
fur
Actively
respiring
cells
containing
electron
transport
chains
Transcription of
pdt
4
pdt
locus
Translation of
mRNA to produce
protein products
5
Slightly
alkaline
conditions
(pH ~8)
1
e -
6
Synthesis of PDTC
Cu *
7
Export of PDTC
PDTC-Cu
activation
(reduction)
9
PDTC
8
Cu binding to PDTC
Cu
CCl 4
Cu
10
CO 2 + nonvolatile products
Pseudomonas
stutzeri KC
Figure 9.6. Model of CT transformation by P. stutzeri KC in the presence of actively respiring cells:
a slightly alkaline pH (step 1) causes a decrease in iron bioavailability (step 2), activating fur
response (step 3), transcription of pdt genes (step 4), translation of mRNA transcripts (step 5),
synthesis of PDTC (step 6), secretion of PDTC (step 7). Secreted PDTC interacts with transition
metals, such as Cu (step 8). When it binds Cu and is reduced at the cell membrane of an actively
respiring cell (step 9), the complex is activated for CT transformation (step 10).
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