Strain-specific ureolytic microbial calcium carbonate precipitation.

Area of Science:

• Microbiology
• Biomineralization
• Environmental Science

Background:

• Ureolytic microbes precipitate calcium carbonate (CaCO(3)), forming crystal aggregates.
• Observed morphological variations in CaCO(3) precipitates suggested strain-specific differences.
• Initial hypothesis proposed differences in microbial species or functional attributes.

Purpose of the Study:

• To investigate the causes of morphological differences in ureolytic microbial CaCO(3) precipitation.
• To analyze urease gene diversity and enzyme kinetics among selected bacterial isolates.
• To determine the role of calcium in strain-specific calcification.

Main Methods:

• Isolation and selection of 12 bacterial strains based on CaCO(3) morphology.
• Phylogenetic analysis using 16S rRNA gene sequencing.
• Urease gene diversity assessment via PCR-denaturing gradient gel electrophoresis (DGGE).
• Enzyme kinetics analysis (K(m) and V(max)) of crude urease extracts.
• Evaluation of urease activity in the presence of calcium.

Main Results:

• All isolates belonged to the Bacillus sphaericus group.
• DGGE analysis revealed significant urease gene diversity, with some isolates showing multiple bands.
• Substrate affinities and hydrolysis rates varied considerably among strains.
• Urease activity increased up to 10-fold in the presence of calcium for certain isolates.
• Strain-specific calcification was demonstrated, linked to urease expression and calcium response.

Conclusions:

• Bacterial urease expression and response to calcium are key drivers of CaCO(3) precipitation morphology.
• Significant diversity exists in urease genes and enzyme kinetics within closely related bacterial strains.
• Microbial control over biomineralization processes is modulated by specific enzymatic and ionic interactions.