2000 Volume 15 Issue 3 Pages 161-171
We studied calcareous concretions from the Epte river.Two strains, Bacillus sp.and Bacillus licheniformis, were isolated from these concretions.The aim of this study was to follow calcium carbonate formation at the early stages of the mineralizing process and to identify crystals by Fourier transform infrared spectroscopy(FTIRS).Bacillus cereus and Bacillus sp.associated with Bacillus licheniformis were cultured on a calcium-enriched medium.Crystal formation was assessed by sampling at 20 h, 48 h, 72 h, 1 week and 2 weeks.After being picked up from the culture and air dried, crystals were identified by FTIRS.An experiment without bacteria inoculum was performed as control.No crystal was obtained in the control experiment.Crystals were present in all cultures of Bacillus species.We observed several steps in the formation of calcium deposits.In most experiments, vaterite appeared as the initial crystalline phase and was followed by carbapatite as a transient phase.Lastly, calcite crystals appeared in all cases within two weeks.Differences in both kinetics and abundance of minerals were observed depending on the tested strain, Bacillus cereus or Bacillus licheniformis and Bacillus sp.association.FTIRS is a sensitive and suitable technique for studying the early stages of Bacillus-induced crystallization.
