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International Journal of Environment Science and Technology
Center for Environment and Energy Research and Studies (CEERS)
ISSN: 1735-1472
EISSN: 1735-2630
Vol. 6, No. 4, 2009, pp. 557-562
Bioline Code: st09061
Full paper language: English
Document type: Research Article
Document available free of charge

International Journal of Environment Science and Technology, Vol. 6, No. 4, 2009, pp. 557-562

 en The influence of picocyanobacterial photosynthesis on calcite precipitation
Kosamu, I. B. M. & Obst, M.

Abstract

This study assessed the role of picocyanobacterial photosynthesis in the induction of calcite precipitation. It aimed at establishing whether photosynthetic uptake of bicarbonate by Synechoccoccus check for this species in other resources cells leads to calcite nucleation. The precipitation of calcite was initiated by addition of previously washed cyanobacterial cells of Synechococcus strain PCC 7942 to solutions of calcium carbonate at different saturation levels with respect to calcite. Precipitation experiments were performed under controlled laboratory conditions in two set-ups: one in which photosynthesis was inhibited using a herbicide called Diuron and the other one in which photosynthesis was taking place. During the experiments, a pH meter monitored the pH and ion selective electrodes monitored concentrations of carbonate and calcium ions. The morphology of the precipitated crystals was analysed using Scanning Electron Microscopy. When the kinetics of calcium carbonate nucleation by the Synechococcus cells were compared for the two sets of experiments, there were very little differences. In fact, the induction times for precipitation reactions with photosynthesis were shorter due to the uptake of carbon dioxide. It is therefore, concluded that photosynthesis does not directly influence the nucleation of calcite at the surface of Synechococcus cells with sufficient supply of carbon dioxide, i.e. cells took up carbon dioxide and not bicarbonate. The microscopic observations, however, provided some evidence that picocyanobacterial cell walls act as a template for calcite nucleation.

Keywords
Bacteria; Biomineralization; Crystal morphology; Ion selective electrodes; Scanning electron microscopy

 
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