Engineering Pseudomonas Putida To Minimize
Clogging During Biostimulation
Author(s)
A. Matin, D. Hahm & D. F. Ackerley
Abstract
Bacterial bioremediation is a safe and inexpensive means of decontaminating
environmental pollution. However, low nutrient concentrations at polluted sites
frequently limit bioremediating activity. Biostimulation by exogenous
application of nutrients does not always promote effective transformation of
pollutants, and the high levels of biomass that result can cause clogging around
feeding ports, further constraining this strategy. To overcome these limitations
we propose the application of starvation promoters to selectively express genes
that are useful in bioremediation at maximal levels in nutrient-limited cells. Here
we show that placing toluene monoxygenase (TMO) genes under control of the
Pstarv1 starvation promoter in Pseudomonas putida MK1 brought about an
8-fold increase in the rate of phenol degradation by stationary-phase cells over
exponentially growing cells. Under nutrient-limiting conditions these cells were
also able to transform trichloroethylene with a conversion efficiency
approximately 64-fold greater than unmodified cells, which only express
appreciable levels of TMO in exponential phase. We also mapped and characterized the native promoter of chrR, a P. putida gene encoding a chromate-reducing enzyme, and show that it is likely to be under the transcriptional control
of sigma 32, a heat shock and starvation regulated sigma factor. Consistent with this
observation, P. putida cells grown at different dilution rates in a chemostat
exhibited maximal chromate-reducing activity at low growth rates. These results
are promising for maximizing the expression of chrR under field conditions for
chromate bioremediation.
Keywords: bioremediation, biostimulation, phenol, trichloroethylene,
hexavalent chromium, toluene monoxygenase, chromate reductase, starvation
promoter.
Keywords
bioremediation, biostimulation, phenol, trichloroethylene,
hexavalent chromium, toluene monoxygenase, chromate reductase, starvation
promoter.
Related Book
Other papers in this volume
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