Bacterially induced mineralization of calcium carbonate: the role of exopolysaccharides and capsular polysaccharides.
Bacterially induced carbonate mineralization has been proposed as a new method for the restoration of limestones in historic buildings and monuments. We describe here the formation of calcite crystals by extracellular polymeric substances isolated from Bacillus firmus and Bacillus sphaericus. We isolated bacterial outer structures (glycocalix and parietal polymers), such as exopolysaccharides (EPS) and capsular polysaccharides (CPS) and checked for their influence on calcite precipitation. CPS and EPS extracted from both B. firmus and B. sphaericus were able to mediate CaCO3 precipitation in vitro. X-ray microanalysis showed that in all cases the formed crystals were calcite. Scanning electron microscopy showed that the shape of the crystals depended on the fractions utilized. These results suggest the possibility that biochemical composition of CPS or EPS influences the resulting morphology of CaCO3. There were no precipitates in the blank samples. CPS and EPS comprised of proteins and glycoproteins. Positive alcian blue staining also reveals acidic polysaccharides in CPS and EPS fractions. Proteins with molecular masses of 25-40 kDa and 70 kDa in the CPS fraction were highly expressed in the presence of calcium oxalate. This high level of synthesis could be related to the binding of calcium ions and carbonate deposition.
Ercole
Claudia
C
Department of Basic and Applied Biology, University of L'Aquila, 67010 L'Aquila, Italy. claudia.ercole@univaq.it
Cacchio
Paola
P
Botta
Anna Lucia
AL
Centi
Valeria
V
Lepidi
Aldo
A
D001407:Bacillus / Q000378:metabolism* / Q000648:ultrastructure; D016667:Bacterial Capsules / Q000378:metabolism* / Q000648:ultrastructure; D002118:Calcium / Q000737:chemistry / Q000378:metabolism; D002119:Calcium Carbonate / Q000737:chemistry* / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D017348:Microscopy, Electron, Scanning Transmission; D008858:Microscopy, Phase-Contrast; D011135:Polysaccharides, Bacterial / Q000737:chemistry* / Q000378:metabolism
D011135:Polysaccharides, Bacterial; D002119:Calcium Carbonate; D002118:Calcium