Article

Strain-Specific Ureolytic Microbial Calcium Carbonate Precipitation

Laboratory of Microbial Ecology and Technology (LabMET), Ghent University, B-9000 Ghent, Belgium.
Applied and Environmental Microbiology (Impact Factor: 3.67). 09/2003; 69(8):4901-9. DOI: 10.1128/AEM.69.8.4901-4909.2003
Source: PubMed

ABSTRACT

During a study of ureolytic microbial calcium carbonate (CaCO3) precipitation by bacterial isolates collected from different environmental samples, morphological differences were observed
in the large CaCO3 crystal aggregates precipitated within bacterial colonies grown on agar. Based on these differences, 12 isolates were selected
for further study. We hypothesized that the striking differences in crystal morphology were the result of different microbial
species or, alternatively, differences in the functional attributes of the isolates selected. Sequencing of 16S rRNA genes
showed that all of the isolates were phylogenetically closely related to the Bacillus sphaericus group. Urease gene diversity among the isolates was examined by using a novel application of PCR-denaturing gradient gel
electrophoresis (DGGE). This approach revealed significant differences between the isolates. Moreover, for several isolates,
multiple bands appeared on the DGGE gels, suggesting the apparent presence of different urease genes in these isolates. The
substrate affinities (Km) and maximum hydrolysis rates (Vmax) of crude enzyme extracts differed considerably for the different strains. For certain isolates, the urease activity increased
up to 10-fold in the presence of 30 mM calcium, and apparently this contributed to the characteristic crystal formation by
these isolates. We show that strain-specific calcification occurred during ureolytic microbial carbonate precipitation. The
specificity was mainly due to differences in urease expression and the response to calcium.

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