occurring at a scale ranging from the microscopic one of cells (order of mm) to that
of geological formations (order of Km). The mechanisms of precipitation and the
function of this process within both the cell physiology and the microbial ecology
of the precipitating organism still remains largely unresolved (Yates and Robbins
1999; Rivadeneyra et al. 1994). In particular, very less is known on the molecular
basis of the process.
Improving our knowledge on molecular mechanisms of BCCP would be useful
for applied purposes.
This chapter starts with a brief overview of the main commonly recognized features of BCCP (Sect. 5.2) followed by the description of interactions between bacterial metabolism and BCCP (Sect. 5.3) and cell surface
and BCCP (Sect. 5.4), with particular focus on what is known on molecular
aspects.
5.2 General Features of Bacterial Calcium Carbonate
Mineralization
5.2.1 Calcium Carbonate Mineralization Terms and Processes
This Section deals with commonly recognized features and mechanisms of bacterial
CC mineralization both in natural environments and in the laboratory.
Some introductive clarifications are necessary regarding the terminology. The
first one regards the terms precipitation and mineralization. According to Beveridge
(1989), there is a subtle but significant difference between precipitation and mineralization. Metal precipitates are hydrous, amorphous aggregates, whereas minerals
are much more anhydrous and crystalline. The former are converted to the latter by
lithification; water is slowly drawn out by heat and compaction during solidification. In this context, the precipitates found on bacterial surfaces are early stages
of mineral development; in a natural setting, bona fide minerals should be long
in forming. Nevertheless, in this chapter, the two terms, CC precipitation and
CC mineralization, will be considered synonymous.
The second clarification regards the term biomineralization. Published definitions
of the term biomineral vary widely (Dupraz et al. 2009) but their use is not banal
since their significance is linked to the role of organisms in mineralization. In general
terms, biomineralization is the process through which organisms are involved in
mineral formation, as a result of cellular activity that fosters the necessary physical
and chemical conditions for such a formation and growth to take place (Ben Omar
et al. 1997). It refers to a mineral that is produced by living organisms and consists of
both mineral and organic components (Weiner and Dove 2003).
From an evolutionary point of view it can be stated, without any doubt, that
biomineralization processes originated from bacterial activity (Ben Omar et al.
1997). The majority of the described biominerals contain calcium as their main
5 Molecular Basis of Bacterial Calcium Carbonate Precipitation
115
of geological formations (order of Km). The mechanisms of precipitation and the
function of this process within both the cell physiology and the microbial ecology
of the precipitating organism still remains largely unresolved (Yates and Robbins
1999; Rivadeneyra et al. 1994). In particular, very less is known on the molecular
basis of the process.
Improving our knowledge on molecular mechanisms of BCCP would be useful
for applied purposes.
This chapter starts with a brief overview of the main commonly recognized features of BCCP (Sect. 5.2) followed by the description of interactions between bacterial metabolism and BCCP (Sect. 5.3) and cell surface
and BCCP (Sect. 5.4), with particular focus on what is known on molecular
aspects.
5.2 General Features of Bacterial Calcium Carbonate
Mineralization
5.2.1 Calcium Carbonate Mineralization Terms and Processes
This Section deals with commonly recognized features and mechanisms of bacterial
CC mineralization both in natural environments and in the laboratory.
Some introductive clarifications are necessary regarding the terminology. The
first one regards the terms precipitation and mineralization. According to Beveridge
(1989), there is a subtle but significant difference between precipitation and mineralization. Metal precipitates are hydrous, amorphous aggregates, whereas minerals
are much more anhydrous and crystalline. The former are converted to the latter by
lithification; water is slowly drawn out by heat and compaction during solidification. In this context, the precipitates found on bacterial surfaces are early stages
of mineral development; in a natural setting, bona fide minerals should be long
in forming. Nevertheless, in this chapter, the two terms, CC precipitation and
CC mineralization, will be considered synonymous.
The second clarification regards the term biomineralization. Published definitions
of the term biomineral vary widely (Dupraz et al. 2009) but their use is not banal
since their significance is linked to the role of organisms in mineralization. In general
terms, biomineralization is the process through which organisms are involved in
mineral formation, as a result of cellular activity that fosters the necessary physical
and chemical conditions for such a formation and growth to take place (Ben Omar
et al. 1997). It refers to a mineral that is produced by living organisms and consists of
both mineral and organic components (Weiner and Dove 2003).
From an evolutionary point of view it can be stated, without any doubt, that
biomineralization processes originated from bacterial activity (Ben Omar et al.
1997). The majority of the described biominerals contain calcium as their main
5 Molecular Basis of Bacterial Calcium Carbonate Precipitation
115