Calcifying Bacteria Flexibility in Induction of CaCO₃ Mineralization

Area of Science:

• Biogeochemistry
• Materials Science
• Microbiology

Background:

• Microbially induced calcium carbonate precipitation (MICP) offers a green technology for cement self-healing and biomaterials.
• The precise role of bacteria in CaCO3 nucleation, growth, and aggregation requires further clarification.

Purpose of the Study:

• To screen ureolytic microorganisms for their MICP capabilities.
• To analyze MICP abilities in both urea-supplemented and urea-deficient environments.
• To investigate bacterial mechanisms for inducing CaCO3 precipitation.

Main Methods:

• Screening of ureolytic microorganisms.
• Cultivation in urea-supplemented and urea-deficient media.
• Analysis of CaCO3 precipitation and bacterial growth.
• Cement crack repair assessment using selected bacterial strains.

Main Results:

• Nine ureolytic bacteria candidates demonstrated high urease activity and efficient CaCO3 biomineralization in urea-rich media.
• All tested ureolytic bacteria induced CaCO3 precipitation even in urea-deficient media, albeit at lower pH.
• Five bacterial strains, including *B. licheniformis* DSMZ 8782, successfully repaired micro-cracks in cement samples.
• *B. licheniformis* DSMZ 8782 showed slower polymorph transformation in urea-deficient media, suggesting adaptable biomineralization mechanisms.

Conclusions:

• Ureolytic bacteria can induce CaCO3 precipitation through diverse mechanisms, independent of urea availability.
• MICP by specific bacterial strains holds significant potential for self-healing concrete and novel biomaterial development.
• Bacterial adaptability in CaCO3 biomineralization is key for practical applications in construction and materials science.