Sporosarcina pasteurii can Efficiently Precipitate Calcium Carbonate at High Salt Concentration

Abstract

The present work explores the adaptive behavior of well-known ureolytic bacterial strain namely Sporosarcina pasteurii for microbial-induced calcite precipitation (MICP) under saline environment. MICP activity was observed up to 10% NaCl supplementation and confirmed by several characterization techniques viz. scanning electron microscopy (SEM), X-ray diffraction (XRD), and thermogravimetric analysis (TGA). The urease activity did not show appreciable decline till 5% NaCl supplementation but beyond that drastic reduction was observed though MICP process continued. These results indicated a shift in the biological pathway for MICP process at higher salt concentrations. This was confirmed by estimation of ammonium ion concentration which was approximately 4 µg/ml with 10% NaCl supplementation as compared to 8.5 µg/ml at 0% NaCl supplementation. To provide an insight on the nature of protein expressed, combination of liquid chromatography-mass spectrometry (nano-LC-MS) approaches along with an exponentially modified protein abundance index (emPAI) methodology were explored. The findings suggest the presence of significant number of osmoregulatory proteins substantiating halophilic adaptation of S. pasteurii and bicarbonate transport mediated precipitation at higher levels of salinity. Further, co-precipitation of CaCl₂ and MgSO₄ was also confirmed with SEM and energy dispersive spectroscopy (EDS) mapping under higher saline environment thus substantiating the efficacy of the strain.

Keywords:

• Salinity
• MICP
• liquid chromatography-mass spectrometry
• protein abundance
• ureolytic bacteria

Acknowledgments

The authors are grateful to the Centre for Cellular and Molecular Platforms (C-CAMP) for performing the LCMS/MS run. Authors also acknowledge Advanced Facility for Microscopy and Microanalysis (AFMM) of Indian Institute of Science, Bangalore for SEM, Indian Science Technology and Engineering facilities Map (I-STEM) for XRD and Solid State and Structural Chemistry Unit (SSU) for TGA analysis respectively.

Additional information

Funding

The present work was financially supported by the Department of Biotechnology, Ministry of Science and Technology, GOI through a grant under BioCare Scheme [BT/PR31844/BIC/101/1206/2019] and partially by the Indian Space Research Organisation (ISRO), Bangalore [ISTC0415].