Calcium carbonate precipitation induced by calcifying bacteria in culture experiments: Influence of the medium on morphology and mineralogy

Bacterially induced calcium carbonate precipitation, recognized as a common phenomenon in nature, has been extensively investigated owing to its beneficial and harmful effects on calcareous stones, namely environmental friendly and potential approach for consolidation deteriorated artworks and aesthetic and physicochemical damage to intact stones. Here four bacterial strains, identified as Pseudomonas sp. (N9), Bacillus cereus (T6), Lysinibacillus sphaericus (T5) and Bacillus sp. (T4), were isolated from white plaques covering historical white marble and proven to have the ability to induce precipitations of calcium carbonate. However, the size and morphology of crystals exhibit a distinct difference after inoculation of specific strain, even in the presence of same medium the crystals tend to vary with different isolates. XRD analysis shows that both calcite and vaterite were simultaneously present in strains N9- and T6-inoculated M-3P medium, while only calcite was detected in M-3P medium after inoculation with strains T5 and T4. Interestingly, in strains T6-and T5-inoculated B-4 culture medium, the precipitations were mainly composed of calcite and vaterite, with a small amount of weddellite only obtained from the former, while calcium-containing crystals were also absent from strains N9- and T4-inoculated medium. Moreover, all of the precipitated crystals present in both culture medium correspond to pH analyses.