nucleation sites for further mineral formation (Fortin et al. 1995). Microorganisms
interact with minerals for creating a more hospitable surrounding by extraction of
nutrients and sequestration of toxic substances. Microbes use minerals as sources
and sinks of electrons, for coupled oxidation–reduction reactions. Many of these
reactions enable the release and capture of energy from unstable or metastable
minerals (Shock 2009). Deep-sea minerals in polymetallic nodules, Fe–Mn crusts,
and hydrothermal vents are not only formed by abiogenic mineralization but also by
free-living and biofilm-forming bacteria which form matrix for Mn deposition.
Here the mineralization processes proceed in close association with organic
molecules or matrices. It can be an either induced (biological–chemical) or a
controlled (enzymatic) process and the details of the processes and the references
have been described by Wang and M€ uller (2009). Besides, in order to understand
the biogeochemical phenomena occurring in the Mn-rich marine environments,
several microbiological studies have focused on hydrothermal vents and Fe–Mn
encrusted seamounts in the recent years (Davis et al. 2009; Emerson 2009; Glazer
and Rouxel 2009; Rassa et al. 2009; Sudek et al. 2009). Few extended their research
on biologically induced mineralization (Douglas and Beveridge 1998; Wang et al.
2009a, b; Dong 2010). Wang et al. (2009b) examined the biogenic components of
the crust and He et al. (2008) examined the microbial community composition of
Iron–Manganese nodules using sophisticated analytical tools. They found
acidobacteria and proteobacteria in nodules and associated sediments. The
firmicutes were restricted to nodules and the soils had more acidobacteria and
Verrucomicrobia compared to nodules. Advancement in element-specific mapping
of rock surfaces revealed hot spots of Mn accumulation in microbial biofilms
(Templeton and Knowles 2009).
The mineral phases produced by bacteria are mostly amorphous and sometimes
poorly crystalline. The crystallization process occurs with prolonged incubation
time (Tazaki 2005) and the characteristic oxides thus produced are not identical to
known synthetic solids possibly, because of solid-phase incorporation of biomolecular constituents (Parikh and Chorover 2005). It is observed that surficial proteins
associate with Mn oxidation during the production of a poorly crystalline Mn(IV)
phase. The formation of mixed phase minerals like hausmannite (Mn 3 O 4 ),
feiknechtite (b-MnOOH), manganite (g-MnOOH), and Na-buserite following Mn
(II) oxidation by Bacillus SG-1 was reported by Mann et al. (1988) and Mandernack
et al. (1995). Whereas, a todorokite-like mineral was found to be produced by
Leptothrix discophora Strain SP-6 (Kim et al. 2003) and MnOx produced by
Pseudomonas putida Strain MnB1 was most similar to “acid” birnessite (Villalobos
et al. 2003). Recent understanding about the genes and proteins involved in Mn
oxidation help to spread its application in biotechnology. The gene mnxG responsible for Mn oxidation in Bacillus SG-1 (van Wassbergen et al. 1996), cumA in
Pseudomonas putida GB-1 (Brouwers et al. 1999), mofA in Leptothrix discophora
SS-1 (Corstjens et al. 1997; Brouwers et al. 2000a), moxA in Pedomicrobium sp.
ACM3067 (Ridge et al. 2007), and mopA in Aurantimonas manganoxidans Strain.
SI85-9A1 and Erythrobacter sp Strain. SD-21 (Anderson et al. 2009b) could be
cloned and the products expressed under laboratory condition.
64
P.P. Sujith and P.A. Loka Bharathi
interact with minerals for creating a more hospitable surrounding by extraction of
nutrients and sequestration of toxic substances. Microbes use minerals as sources
and sinks of electrons, for coupled oxidation–reduction reactions. Many of these
reactions enable the release and capture of energy from unstable or metastable
minerals (Shock 2009). Deep-sea minerals in polymetallic nodules, Fe–Mn crusts,
and hydrothermal vents are not only formed by abiogenic mineralization but also by
free-living and biofilm-forming bacteria which form matrix for Mn deposition.
Here the mineralization processes proceed in close association with organic
molecules or matrices. It can be an either induced (biological–chemical) or a
controlled (enzymatic) process and the details of the processes and the references
have been described by Wang and M€ uller (2009). Besides, in order to understand
the biogeochemical phenomena occurring in the Mn-rich marine environments,
several microbiological studies have focused on hydrothermal vents and Fe–Mn
encrusted seamounts in the recent years (Davis et al. 2009; Emerson 2009; Glazer
and Rouxel 2009; Rassa et al. 2009; Sudek et al. 2009). Few extended their research
on biologically induced mineralization (Douglas and Beveridge 1998; Wang et al.
2009a, b; Dong 2010). Wang et al. (2009b) examined the biogenic components of
the crust and He et al. (2008) examined the microbial community composition of
Iron–Manganese nodules using sophisticated analytical tools. They found
acidobacteria and proteobacteria in nodules and associated sediments. The
firmicutes were restricted to nodules and the soils had more acidobacteria and
Verrucomicrobia compared to nodules. Advancement in element-specific mapping
of rock surfaces revealed hot spots of Mn accumulation in microbial biofilms
(Templeton and Knowles 2009).
The mineral phases produced by bacteria are mostly amorphous and sometimes
poorly crystalline. The crystallization process occurs with prolonged incubation
time (Tazaki 2005) and the characteristic oxides thus produced are not identical to
known synthetic solids possibly, because of solid-phase incorporation of biomolecular constituents (Parikh and Chorover 2005). It is observed that surficial proteins
associate with Mn oxidation during the production of a poorly crystalline Mn(IV)
phase. The formation of mixed phase minerals like hausmannite (Mn 3 O 4 ),
feiknechtite (b-MnOOH), manganite (g-MnOOH), and Na-buserite following Mn
(II) oxidation by Bacillus SG-1 was reported by Mann et al. (1988) and Mandernack
et al. (1995). Whereas, a todorokite-like mineral was found to be produced by
Leptothrix discophora Strain SP-6 (Kim et al. 2003) and MnOx produced by
Pseudomonas putida Strain MnB1 was most similar to “acid” birnessite (Villalobos
et al. 2003). Recent understanding about the genes and proteins involved in Mn
oxidation help to spread its application in biotechnology. The gene mnxG responsible for Mn oxidation in Bacillus SG-1 (van Wassbergen et al. 1996), cumA in
Pseudomonas putida GB-1 (Brouwers et al. 1999), mofA in Leptothrix discophora
SS-1 (Corstjens et al. 1997; Brouwers et al. 2000a), moxA in Pedomicrobium sp.
ACM3067 (Ridge et al. 2007), and mopA in Aurantimonas manganoxidans Strain.
SI85-9A1 and Erythrobacter sp Strain. SD-21 (Anderson et al. 2009b) could be
cloned and the products expressed under laboratory condition.
64
P.P. Sujith and P.A. Loka Bharathi