Bacteria produces extracellular polymeric substances (EPS) which have also been
exposed to be involved in the method of biocalcification by capturing and serving as
a nucleation site. Calcium carbonate formation was occur through the activity of a
peptide matrix in Pseudomonas fluorescens, and the major contributing amino acids
like glutamic acid, alanine, aspartic acid, and glycine. The change composition and
concentration of EPS have an impact on both the morphology and the mineralogy of
the carbonate crystals (Braissant et al. 2003). EPS also seems to be involved in
increasing the size of the crystals by causing the aggregation of smaller crystals
(Dania et al. 2009).
11.4 Metabolic Pathways of Chemolithotrophic Bacteria/
Autotrophic Bacteria
Some microorganisms play an essential role in ecosystems by providing a continuous supply of organic carbon for heterotrophs. The Calvin–Benson–Bassham cycle
(Calvin cycle) represents the fundamental autotrophic (chemotrophic or
phototrophic) carbon fixation pathway. There are several CO 2 fixation pathways
found in microorganism which is present in extreme environments such as high
temperature or anaerobic or acidic conditions. (1) Reductive cabroxylic acid (TAC)
cycle, (2) the reductive acetyl coenzyme A pathway, (3) the 3-hydroxypropionate
Fig. 11.1 Schematic representation of suggested bacterial calcium metabolism and subsequent
CaCO 3 precipitation under high-pH and high-Ca
2+ extracellular conditions (Hammes and
Verstraete 2002)
238
R. K. Bharti et al.
exposed to be involved in the method of biocalcification by capturing and serving as
a nucleation site. Calcium carbonate formation was occur through the activity of a
peptide matrix in Pseudomonas fluorescens, and the major contributing amino acids
like glutamic acid, alanine, aspartic acid, and glycine. The change composition and
concentration of EPS have an impact on both the morphology and the mineralogy of
the carbonate crystals (Braissant et al. 2003). EPS also seems to be involved in
increasing the size of the crystals by causing the aggregation of smaller crystals
(Dania et al. 2009).
11.4 Metabolic Pathways of Chemolithotrophic Bacteria/
Autotrophic Bacteria
Some microorganisms play an essential role in ecosystems by providing a continuous supply of organic carbon for heterotrophs. The Calvin–Benson–Bassham cycle
(Calvin cycle) represents the fundamental autotrophic (chemotrophic or
phototrophic) carbon fixation pathway. There are several CO 2 fixation pathways
found in microorganism which is present in extreme environments such as high
temperature or anaerobic or acidic conditions. (1) Reductive cabroxylic acid (TAC)
cycle, (2) the reductive acetyl coenzyme A pathway, (3) the 3-hydroxypropionate
Fig. 11.1 Schematic representation of suggested bacterial calcium metabolism and subsequent
CaCO 3 precipitation under high-pH and high-Ca
2+ extracellular conditions (Hammes and
Verstraete 2002)
238
R. K. Bharti et al.