Influence of environmental temperature on biocalcification by non-sporing freshwater bacteria

The process of biocalcification, recognised as precipitation of calcium carbonate, has been described as a widespread phenomenon associated with a wide range of different bacterial species. This biocalcifying activity, and factors that affect it, have been widely studied in moderately halophilic bacteria but there is a lack of information on factors that affect biocalcification by freshwater bacteria. In this paper, we study how temperature can affect biocalcification by freshwater bacteria that potentially could be used for the process of bioconsolidation during conservation. Ten isolates were characterised by standard biochemical and API 20NE tests. Their biocalcifying activity was studied at temperatures between 10 and 40C in B4 liquid medium. Mineralogical and quantitative analyses of the crystals were carried out by XRD, and morphological studies by SEM. Biocalcification only occurred when bacteria were present and were able to grow. Carbonate precipitation by bacteria increased with time and temperature of incubation. Temperature affected not only the amount of precipitation but also crystal quality and morphology. As bioconsolidant agents, these organisms could be applied to stone when the temperature does not exceed 40C depending on the type of isolate.