loss of mercury by volatilization. The use of this metabolic
capacity (reduction of inorganic mercury to volatile elemental mercury) has been proposed for contaminated sites,
wastes or wastewaters contaminated with mercury (Saouter
et al. 1994). In this context, the volatile mercury product can
be recovered by chemical trapping.
16.10 Conclusion
The immense diversity of metabolic capabilities of
microorganisms (cf. Sect. 3.3) allows them to degrade virtually all organic compounds of natural or anthropogenic
(xenobiotics) origins, including those that are a source of
environmental pollution. These processing capacities of
molecules rely on the complementary metabolisms between
different populations within a community subject to a pollutant (cf. Sect. 16.8). These capabilities are also due to the high
genetic plasticity characteristic prokaryotic that results in
genetic transfer and recombination or even in the “creation”
of new genes (e.g., lindane and atrazine). All these properties
explain the importance of the role of microorganisms in the
natural attenuation or the natural elimination of pollutants in
the environment. The observation of these natural attenuation
phenomena has led to numerous studies conducted using
cultures in flasks and fermenters, in microcosms containing
low volume samples which have yield a sophisticated knowledge of degradation pathways and parameters that regulate
them. The efficiency of microbiological treatments is first
confirmed by tests carried out in the field (experimental
sites, greenhouses) that resulted in treatments at the industrial
scale of soils, sediments, aquifers (groundwater), sand
beaches. The success of these technologies is confirmed by
the number of patents in this area and by the proliferation of
commercial companies that offer and commercialize
microbiological treatments, thus proving that these treatments
are economically feasible. Like any emerging technology,
bioremediation develops in a scientific context that is still
far from being fully mastered.
Questions that remain unanswered are essentially twofold.
One concerns the bioaugmentation in natural ecosystems and
its possible consequences (i) on the indigenous microbial
community and (ii) on the risks of releasing nonindigenous
and/or genetically modified microorganisms into the environment. Strict regulation is now in place to control this
type of treatment. The introduction of isolated and/or
genetically modified microorganisms in environments
where they were not present naturally raises the question
of their future and their effects on the evolution of these
ecosystems. The few available observations tend to reinforce the idea of the existence of a direct link between the
decline of a given function and the survival of microbial
operators. The mobility and transience of the genetic
elements involved do not allow making it a general rule.
Under favorable conditions of saprophytism, some strains
could loss plasmids that are becoming useless. Thus, as
generations increase, some catabolic properties involved in
the biodegradation of pollutants tend to disappear, even
though the supporting microorganisms continue to proliferate. These microbial invasions, some of which are visible
in aquatic ecosystems, remain cryptic in the soil and are
difficult to characterize except by their potential impact on
the functionality of the ecosystem.
The other limitation is operational and concerns the transition
from the laboratory to the natural environment. A perfect
knowledge of the site, its physical, chemical, and
biological characteristics, is the only likely way to identify
limiting factors. Thus, treatments that are mature and have
resulted in large-scale applications – sewage treatment,
waste treatment – are implemented in closed/sealed
systems (sewage plants, lagoons, ponds, fermentors) that
allow a better control of the treatment functioning.
Despite these restrictions, microbiologically based pollution treatments have a good future and their application is
undeniable in terms of sustainable development.
References
Abbasnezhad H, Gray M, Foght JM (2011) Influence of adhesion on
aerobic biodegradation and bioremediation of liquid hydrocarbons.
Appl Microbiol Biotechnol 92:653–675
Abramowicz DA (1990) Aerobic and anaerobic biodegradation of
PCBs: a review. Crit Rev Biotechnol 10:241–251
Adrian L, Dudkova ´ V, Demnerova ´ K, Bedard DL (2009)
“Dehalococcoides” sp. Strain CBDB1 extensively dechlorinates
the commercial polychlorinated biphenyl mixture Arochlor 1260.
Appl Environ Microbiol 75:4516–4524
Alder AC, Ha ¨ggblom MM, Oppenheimer SR, Young LY (1993)
Reductive dechlorination of polychlorinated biphenyls in anaerobic
sediments. Environ Sci Technol 27:530–538
Alexander M (1965) Biodegradation: problems of molecular recalcitrance and microbial infallibility. Adv Appl Microbiol 7:35–80
Al-Mailem DM, Sorkhoh NA, Al-Awadhi H, Eliyas M, Radwan SS
(2010) Biodegradation of crude oil and pure hydrocarbons by
extre ˆme halophilic archaea from hypersalin coasts of the Arabian
Gulf. Extremophiles 14:321–328
Alvey S, Crowley DE (1996) Survival and activity of an atrazinemineralizing bacterial consortium in rhizosphere soil. Environ Sci
Technol 30:1596–1603
Amaral S (1987) Landfarming of oily wastes: design and operation.
Water Sci Technol 19:75–86
Anderson TA, Kruger EL, Coats JR (1994) Enhanced degradation of a
mixture of three herbicides in the rhizosphere of a herbicide-tolerant
plant. Chemosphere 28:1551–1557
Anderson TA, White DC, Walton BT (1995) Degradation of hazardous
organic compounds by rhizosphere microbial communities. In:
Signh VP (ed) Biotransformations: microbial degradation of health
risk compounds, vol V. Elsevier Science, BV, Amsterdam,
pp 205–225
Anderson RT et al (2003) Stimulating in situ activity of Geobacter
species to remove uranium from groundwater of a uraniumcontaminated aquifer. Appl Environ Microbiol 69:5884–5891
746
J.-C. Bertrand et al.
capacity (reduction of inorganic mercury to volatile elemental mercury) has been proposed for contaminated sites,
wastes or wastewaters contaminated with mercury (Saouter
et al. 1994). In this context, the volatile mercury product can
be recovered by chemical trapping.
16.10 Conclusion
The immense diversity of metabolic capabilities of
microorganisms (cf. Sect. 3.3) allows them to degrade virtually all organic compounds of natural or anthropogenic
(xenobiotics) origins, including those that are a source of
environmental pollution. These processing capacities of
molecules rely on the complementary metabolisms between
different populations within a community subject to a pollutant (cf. Sect. 16.8). These capabilities are also due to the high
genetic plasticity characteristic prokaryotic that results in
genetic transfer and recombination or even in the “creation”
of new genes (e.g., lindane and atrazine). All these properties
explain the importance of the role of microorganisms in the
natural attenuation or the natural elimination of pollutants in
the environment. The observation of these natural attenuation
phenomena has led to numerous studies conducted using
cultures in flasks and fermenters, in microcosms containing
low volume samples which have yield a sophisticated knowledge of degradation pathways and parameters that regulate
them. The efficiency of microbiological treatments is first
confirmed by tests carried out in the field (experimental
sites, greenhouses) that resulted in treatments at the industrial
scale of soils, sediments, aquifers (groundwater), sand
beaches. The success of these technologies is confirmed by
the number of patents in this area and by the proliferation of
commercial companies that offer and commercialize
microbiological treatments, thus proving that these treatments
are economically feasible. Like any emerging technology,
bioremediation develops in a scientific context that is still
far from being fully mastered.
Questions that remain unanswered are essentially twofold.
One concerns the bioaugmentation in natural ecosystems and
its possible consequences (i) on the indigenous microbial
community and (ii) on the risks of releasing nonindigenous
and/or genetically modified microorganisms into the environment. Strict regulation is now in place to control this
type of treatment. The introduction of isolated and/or
genetically modified microorganisms in environments
where they were not present naturally raises the question
of their future and their effects on the evolution of these
ecosystems. The few available observations tend to reinforce the idea of the existence of a direct link between the
decline of a given function and the survival of microbial
operators. The mobility and transience of the genetic
elements involved do not allow making it a general rule.
Under favorable conditions of saprophytism, some strains
could loss plasmids that are becoming useless. Thus, as
generations increase, some catabolic properties involved in
the biodegradation of pollutants tend to disappear, even
though the supporting microorganisms continue to proliferate. These microbial invasions, some of which are visible
in aquatic ecosystems, remain cryptic in the soil and are
difficult to characterize except by their potential impact on
the functionality of the ecosystem.
The other limitation is operational and concerns the transition
from the laboratory to the natural environment. A perfect
knowledge of the site, its physical, chemical, and
biological characteristics, is the only likely way to identify
limiting factors. Thus, treatments that are mature and have
resulted in large-scale applications – sewage treatment,
waste treatment – are implemented in closed/sealed
systems (sewage plants, lagoons, ponds, fermentors) that
allow a better control of the treatment functioning.
Despite these restrictions, microbiologically based pollution treatments have a good future and their application is
undeniable in terms of sustainable development.
References
Abbasnezhad H, Gray M, Foght JM (2011) Influence of adhesion on
aerobic biodegradation and bioremediation of liquid hydrocarbons.
Appl Microbiol Biotechnol 92:653–675
Abramowicz DA (1990) Aerobic and anaerobic biodegradation of
PCBs: a review. Crit Rev Biotechnol 10:241–251
Adrian L, Dudkova ´ V, Demnerova ´ K, Bedard DL (2009)
“Dehalococcoides” sp. Strain CBDB1 extensively dechlorinates
the commercial polychlorinated biphenyl mixture Arochlor 1260.
Appl Environ Microbiol 75:4516–4524
Alder AC, Ha ¨ggblom MM, Oppenheimer SR, Young LY (1993)
Reductive dechlorination of polychlorinated biphenyls in anaerobic
sediments. Environ Sci Technol 27:530–538
Alexander M (1965) Biodegradation: problems of molecular recalcitrance and microbial infallibility. Adv Appl Microbiol 7:35–80
Al-Mailem DM, Sorkhoh NA, Al-Awadhi H, Eliyas M, Radwan SS
(2010) Biodegradation of crude oil and pure hydrocarbons by
extre ˆme halophilic archaea from hypersalin coasts of the Arabian
Gulf. Extremophiles 14:321–328
Alvey S, Crowley DE (1996) Survival and activity of an atrazinemineralizing bacterial consortium in rhizosphere soil. Environ Sci
Technol 30:1596–1603
Amaral S (1987) Landfarming of oily wastes: design and operation.
Water Sci Technol 19:75–86
Anderson TA, Kruger EL, Coats JR (1994) Enhanced degradation of a
mixture of three herbicides in the rhizosphere of a herbicide-tolerant
plant. Chemosphere 28:1551–1557
Anderson TA, White DC, Walton BT (1995) Degradation of hazardous
organic compounds by rhizosphere microbial communities. In:
Signh VP (ed) Biotransformations: microbial degradation of health
risk compounds, vol V. Elsevier Science, BV, Amsterdam,
pp 205–225
Anderson RT et al (2003) Stimulating in situ activity of Geobacter
species to remove uranium from groundwater of a uraniumcontaminated aquifer. Appl Environ Microbiol 69:5884–5891
746
J.-C. Bertrand et al.