G. sulfurreducens). Another way to enrich the solubility of trivalent Fe compounds
in soil or other habitats is to acidify the environment, a process involving the
microbiota of the habitat, organic acids resulting from autolysis, and plant
excretions, respectively. Some Poaceae (wheat, barley) produce phytosiderophores,
similar to siderophores produced by bacteria (Zogg et al. 2018).
Pseudomonas genus members are recognized as having the highest aerobic
degradation capacity of a large number of compounds. Genes responsible for
enzyme synthesis involved in the degradation of these compounds are placed on
plasmids. The Pseudomonas species exhibit resistance to the action of toxic metals.
At P. aeruginosa and P. fluorescens, the Cu resistance was reported. For the strain of
P. putida, the Cu
2+ ion may accumulate at concentrations of 6.5% of the dry weight
of the bacterium in precultivated crops in which the ion SO 4
2À was limitative.
P. stutzeri is resistant to silver by the formation of silver sulfide complexes. A
plasmid of the species P. stutzeri confers resistance to mercury and organomercury
compounds. P. fluorescens detoxify Al and Fe, the trivalent ions being immobilized
in a lipid metabolic complex (phosphatidylethanolamine). Resistance to Zn, Ca, and
Ga is due to the association with phosphatidylethanolamine. P. aeruginosa is
resistant to Hg
2+ ; the resistance to B, Cr, and Te is also determined by plasmid
genes. P. aeruginosa and P. putida accumulate structures containing tellurium in the
periplasmic space. On plasmids, there are genes that determine the resistance of
As. Arsenite [As(III)] to arsenate [As(V)] is reduced to As, which is eliminated
outside the cell. Placing genes responsible for the degradation of pollutant
compounds and genes that confer resistance to the toxic action of HMs on transferable plasmas even interspecifically represent a great advantage. Given the particular
advances in molecular genetics, plasmids or other genetic vectors possessing interspecific mobility may be constructed, the bacteria possessing high biotechnological
efficiency. Of interest for environmental biotechnology are also members of the
genera Burkholderia. Burkholderia cepacia (previously called Pseudomonas
cepacia) and Burkholderia multivorans are aerobic chemoorganoheterotrophic bacteria but can use nitrate as the ultimate acceptor of electrons in anaerobic respiration.
The species of the genus produce countless siderophores. On Fe deficiency
environments (like P. aeruginosa and P. fluorescens) synthesizes salicylic acid, a
high-capacity siderophore compound, for the binding of Fe and other metals. The
degradation of pollutant compounds in the environment is controlled by plasmids
(Cai et al. 2016).
4.5.4 The Role of Microorganisms in Fixing or Mobilizing Metals
in the Soil
The mobility of various organic or inorganic metal compounds in soil, as well as in
other habitats, is closely related to their oxidation state. The energy used by living
systems to carry out vital activities is provided by oxidoreduction reactions catalyzed
by oxidoreductase enzymes (dehydrogenases). The tendency of a chemical compound to accept or yield electrons in biological oxidation reactions is quantitatively
4 Advanced Technologies for Ecological Reconstruction and Bioremediation of. . .
97
in soil or other habitats is to acidify the environment, a process involving the
microbiota of the habitat, organic acids resulting from autolysis, and plant
excretions, respectively. Some Poaceae (wheat, barley) produce phytosiderophores,
similar to siderophores produced by bacteria (Zogg et al. 2018).
Pseudomonas genus members are recognized as having the highest aerobic
degradation capacity of a large number of compounds. Genes responsible for
enzyme synthesis involved in the degradation of these compounds are placed on
plasmids. The Pseudomonas species exhibit resistance to the action of toxic metals.
At P. aeruginosa and P. fluorescens, the Cu resistance was reported. For the strain of
P. putida, the Cu
2+ ion may accumulate at concentrations of 6.5% of the dry weight
of the bacterium in precultivated crops in which the ion SO 4
2À was limitative.
P. stutzeri is resistant to silver by the formation of silver sulfide complexes. A
plasmid of the species P. stutzeri confers resistance to mercury and organomercury
compounds. P. fluorescens detoxify Al and Fe, the trivalent ions being immobilized
in a lipid metabolic complex (phosphatidylethanolamine). Resistance to Zn, Ca, and
Ga is due to the association with phosphatidylethanolamine. P. aeruginosa is
resistant to Hg
2+ ; the resistance to B, Cr, and Te is also determined by plasmid
genes. P. aeruginosa and P. putida accumulate structures containing tellurium in the
periplasmic space. On plasmids, there are genes that determine the resistance of
As. Arsenite [As(III)] to arsenate [As(V)] is reduced to As, which is eliminated
outside the cell. Placing genes responsible for the degradation of pollutant
compounds and genes that confer resistance to the toxic action of HMs on transferable plasmas even interspecifically represent a great advantage. Given the particular
advances in molecular genetics, plasmids or other genetic vectors possessing interspecific mobility may be constructed, the bacteria possessing high biotechnological
efficiency. Of interest for environmental biotechnology are also members of the
genera Burkholderia. Burkholderia cepacia (previously called Pseudomonas
cepacia) and Burkholderia multivorans are aerobic chemoorganoheterotrophic bacteria but can use nitrate as the ultimate acceptor of electrons in anaerobic respiration.
The species of the genus produce countless siderophores. On Fe deficiency
environments (like P. aeruginosa and P. fluorescens) synthesizes salicylic acid, a
high-capacity siderophore compound, for the binding of Fe and other metals. The
degradation of pollutant compounds in the environment is controlled by plasmids
(Cai et al. 2016).
4.5.4 The Role of Microorganisms in Fixing or Mobilizing Metals
in the Soil
The mobility of various organic or inorganic metal compounds in soil, as well as in
other habitats, is closely related to their oxidation state. The energy used by living
systems to carry out vital activities is provided by oxidoreduction reactions catalyzed
by oxidoreductase enzymes (dehydrogenases). The tendency of a chemical compound to accept or yield electrons in biological oxidation reactions is quantitatively
4 Advanced Technologies for Ecological Reconstruction and Bioremediation of. . .
97