proteins are selective Mn transporters involved in response to reactive oxygen.
Diaz-Mireles et al. (2004) affirmed that Fur-like protein Mur (manganese uptake
regulator), a Mn
2+ -responsive transcriptional regulator of Rhizobium leguminosarum, differs from Fur that binds Fe
2+ in g-proteobacteria and engage in Mn
uptake. Groot et al. (2005) identified the expression of three putative Mn transport
systems (mtsCBA, mntH1, and mntH2) besides mntA in Lactobacillus plantarum.
They observed the specific derepression or induction of transport systems upon Mn
2+
limitation, suggesting their role in Mn
2+ homeostasis. Subsequently, Jakubovics
and Valentine (2009) identified the novel Mn
2+ efflux system MntE in Streptococcus pneumoniae. They stated that disruption of the mntE gene could lead to
widespread transcriptional changes that are distinct from responses to extracellular
Mn
2+ .
The expression of 25 kDa cytoplasmic protein was identified as superoxide
dismutase isoenzyme (Mn-SOD) in Arthrobacter sp (Ercole et al. 1999). The
functioning of the protein under both aerobic and anaerobic conditions in
the presence of Mn oxide was found to have additional physiological function.
The higher-molecular-weight surface protein (30 kDa) showed no homology
with any of the identified proteins and its function is yet to be identified. Jung
and Schweisfurth (1979) observed that Pseudomonas sp. Strain MnB1 produced a
heat labile intracellular Mn-oxidizing protein during stationary phase of growth.
Mn-oxidizing protein was not induced by the presence of Mn
2+ , rather it was
particularly dependent on the age of the culture. Likewise, in a comparative
study on Mn oxidation using growing and resting cells of a freshwater bacterial
isolate strain FMn 1, Zapkin and Ehrlich (1983) observed enzymatic nature
of Mn-oxidizing activity in the strain. The activity of the enzyme was inducible.
In a review, Shi (2004) stated that protein phosphatases are metalloenzymes with
active centers containing two metal ions functioning as cofactors. The
Mn-dependent prokaryotic protein O-phosphatases and their function were stated
to add new insight into Mn
2+ homeostasis and protein O-phosphorylation in prokaryotic cells.
3.10 Molecular Biomineralization
Organisms are capable of forming a diverse array of minerals, some of which
cannot be formed inorganically in the biosphere. Biogenic minerals may be amorphous, paracrystalline, or crystalline (Lowenstam 1981). The mineralization processes driven by biological activity involving microorganisms constitute
biomineralization (Wang and M€ uller 2009). The microorganisms and their interaction with geologic materials result in geochemical transformations switching
between soluble and insoluble phases (White et al. 1997). As a result of close
interaction between mineral and bacteria, biomineralization co-occur (Fig. 3.1).
It can lead to precipitation of the metal leachate and formation of metal
oxide coatings on bacterial wall and other inert surfaces contributing directly as
3 Manganese Oxidation by Bacteria: Biogeochemical Aspects
63
Diaz-Mireles et al. (2004) affirmed that Fur-like protein Mur (manganese uptake
regulator), a Mn
2+ -responsive transcriptional regulator of Rhizobium leguminosarum, differs from Fur that binds Fe
2+ in g-proteobacteria and engage in Mn
uptake. Groot et al. (2005) identified the expression of three putative Mn transport
systems (mtsCBA, mntH1, and mntH2) besides mntA in Lactobacillus plantarum.
They observed the specific derepression or induction of transport systems upon Mn
2+
limitation, suggesting their role in Mn
2+ homeostasis. Subsequently, Jakubovics
and Valentine (2009) identified the novel Mn
2+ efflux system MntE in Streptococcus pneumoniae. They stated that disruption of the mntE gene could lead to
widespread transcriptional changes that are distinct from responses to extracellular
Mn
2+ .
The expression of 25 kDa cytoplasmic protein was identified as superoxide
dismutase isoenzyme (Mn-SOD) in Arthrobacter sp (Ercole et al. 1999). The
functioning of the protein under both aerobic and anaerobic conditions in
the presence of Mn oxide was found to have additional physiological function.
The higher-molecular-weight surface protein (30 kDa) showed no homology
with any of the identified proteins and its function is yet to be identified. Jung
and Schweisfurth (1979) observed that Pseudomonas sp. Strain MnB1 produced a
heat labile intracellular Mn-oxidizing protein during stationary phase of growth.
Mn-oxidizing protein was not induced by the presence of Mn
2+ , rather it was
particularly dependent on the age of the culture. Likewise, in a comparative
study on Mn oxidation using growing and resting cells of a freshwater bacterial
isolate strain FMn 1, Zapkin and Ehrlich (1983) observed enzymatic nature
of Mn-oxidizing activity in the strain. The activity of the enzyme was inducible.
In a review, Shi (2004) stated that protein phosphatases are metalloenzymes with
active centers containing two metal ions functioning as cofactors. The
Mn-dependent prokaryotic protein O-phosphatases and their function were stated
to add new insight into Mn
2+ homeostasis and protein O-phosphorylation in prokaryotic cells.
3.10 Molecular Biomineralization
Organisms are capable of forming a diverse array of minerals, some of which
cannot be formed inorganically in the biosphere. Biogenic minerals may be amorphous, paracrystalline, or crystalline (Lowenstam 1981). The mineralization processes driven by biological activity involving microorganisms constitute
biomineralization (Wang and M€ uller 2009). The microorganisms and their interaction with geologic materials result in geochemical transformations switching
between soluble and insoluble phases (White et al. 1997). As a result of close
interaction between mineral and bacteria, biomineralization co-occur (Fig. 3.1).
It can lead to precipitation of the metal leachate and formation of metal
oxide coatings on bacterial wall and other inert surfaces contributing directly as
3 Manganese Oxidation by Bacteria: Biogeochemical Aspects
63