Two other psychrophilic enzymes are also marketed for molecular biology
applications taking advantage of the heat-labile property. Shrimp nuclease selectively degrades double stranded DNA: for instance, it is used for the removal of
carry-over contaminants in PCR mixtures, and then it is heat-inactivated prior to
addition of the template. This enzyme is produced in recombinant form in Pichia
pastoris and is available from Biotec Pharmacon ASA (Norway), USB Corporation
(USA), or Thermo Scientific (UK). Heat-labile uracil-DNA N-glycosylase from
Atlantic cod (Gadus morhua) that presents typical cold adaptation features is also
used to remove DNA contaminants in sequential PCR (Leiros et al. 2003). When
PCR is performed with dUTP instead of dTTP, PCR products become distinguishable from target DNA, and can be selectively degraded by uracil-DNA
N-glycosylase. Following degradation of contaminants, the enzyme is completely
and irreversibly inactivated after heat treatment. Heat-labile uracil-DNA
N-glycosylase, produced in recombinant form in E. coli, is available from Biotec
Pharmacon ASA (Norway) (Margesin and Feller 2010).
6.14.1.4 Bioremediation
Bioremediation is a process to accelerate the natural biodegradation rates through the
optimization of limiting environmental conditions and is an ecologically and economically effective method. Low-temperature biodegradation of organic
contaminants in cold ecosystems is a result of the degradation capacity of the
indigenous psychrophilic microbial population. They transform or mineralize
organic pollutants into less harmful, non-hazardous substances, which are then
integrated into natural biogeochemical cycles.
Several schemes have been implemented successfully at the Arctic and Antarctic
regions to remediate petroleum-contaminated sites (Aislabie and Foght 2008).
Successful on-site treatments include biopiles and land farming, which is now
well-developed for cold regions and offers low-cost treatment of petroleumcontaminated soils (Thomassin-Lacroix et al. 2002). The most widely used bioremediation procedure in cold soils is biostimulation of the indigenous
microorganisms by supplementation of appropriate nutrients (and optimization of
other limiting factors, such as oxygen content, pH, and temperature control); however, care has to be taken to avoid inhibition of biodegradation due to overfertilization (Walworth et al. 2007). Bioaugmentation by inoculating allochthonous
hydrocarbon degraders has been used as a bioremediation option to treat petroleumcontaminated sites in Alaska, Canada, Greenland, and Norway. Bioaugmentation
with non-indigenous or genetically modified/engineered microorganisms is banned
in Antarctica, Norway, Iceland, and Sweden (Filler et al. 2009). The psychrophiles
with specific degradative capabilities based on the transfer of the TOL plasmid from
the mesophile Pseudomonas putida by conjugation to a psychrophile of the same
species; the transconjugant degraded toluene at temperatures as low as 0
C (Kolenc
et al. 1988). Recently, the gene coding for a monooxygenase involved in the
degradation of aromatic hydrocarbons from the mesophile Pseudomonas stutzeri
was recombinantly expressed in the Antarctic Pseudoalteromonas haloplanktis and
performance of such strains has still to be proven (Siani et al. 2006).
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applications taking advantage of the heat-labile property. Shrimp nuclease selectively degrades double stranded DNA: for instance, it is used for the removal of
carry-over contaminants in PCR mixtures, and then it is heat-inactivated prior to
addition of the template. This enzyme is produced in recombinant form in Pichia
pastoris and is available from Biotec Pharmacon ASA (Norway), USB Corporation
(USA), or Thermo Scientific (UK). Heat-labile uracil-DNA N-glycosylase from
Atlantic cod (Gadus morhua) that presents typical cold adaptation features is also
used to remove DNA contaminants in sequential PCR (Leiros et al. 2003). When
PCR is performed with dUTP instead of dTTP, PCR products become distinguishable from target DNA, and can be selectively degraded by uracil-DNA
N-glycosylase. Following degradation of contaminants, the enzyme is completely
and irreversibly inactivated after heat treatment. Heat-labile uracil-DNA
N-glycosylase, produced in recombinant form in E. coli, is available from Biotec
Pharmacon ASA (Norway) (Margesin and Feller 2010).
6.14.1.4 Bioremediation
Bioremediation is a process to accelerate the natural biodegradation rates through the
optimization of limiting environmental conditions and is an ecologically and economically effective method. Low-temperature biodegradation of organic
contaminants in cold ecosystems is a result of the degradation capacity of the
indigenous psychrophilic microbial population. They transform or mineralize
organic pollutants into less harmful, non-hazardous substances, which are then
integrated into natural biogeochemical cycles.
Several schemes have been implemented successfully at the Arctic and Antarctic
regions to remediate petroleum-contaminated sites (Aislabie and Foght 2008).
Successful on-site treatments include biopiles and land farming, which is now
well-developed for cold regions and offers low-cost treatment of petroleumcontaminated soils (Thomassin-Lacroix et al. 2002). The most widely used bioremediation procedure in cold soils is biostimulation of the indigenous
microorganisms by supplementation of appropriate nutrients (and optimization of
other limiting factors, such as oxygen content, pH, and temperature control); however, care has to be taken to avoid inhibition of biodegradation due to overfertilization (Walworth et al. 2007). Bioaugmentation by inoculating allochthonous
hydrocarbon degraders has been used as a bioremediation option to treat petroleumcontaminated sites in Alaska, Canada, Greenland, and Norway. Bioaugmentation
with non-indigenous or genetically modified/engineered microorganisms is banned
in Antarctica, Norway, Iceland, and Sweden (Filler et al. 2009). The psychrophiles
with specific degradative capabilities based on the transfer of the TOL plasmid from
the mesophile Pseudomonas putida by conjugation to a psychrophile of the same
species; the transconjugant degraded toluene at temperatures as low as 0
C (Kolenc
et al. 1988). Recently, the gene coding for a monooxygenase involved in the
degradation of aromatic hydrocarbons from the mesophile Pseudomonas stutzeri
was recombinantly expressed in the Antarctic Pseudoalteromonas haloplanktis and
performance of such strains has still to be proven (Siani et al. 2006).
212
P. K. Mishra et al.