title: Microbially-Mediated Precipitation of Calcium Carbonate Nanoparticles.
abstract: The objective of this study was to investigate the biomineralization of carbonate minerals using microorganisms (Wu Do-1) enriched from rhodoliths. A 16S rRNA sequence analysis showed that Wu Do-1 mainly contained Proteus mirabilis. The pH decreased from 6.5 to 5.3 over the first 4 days of incubation due to microbial oxidation of organic acids, after which it increased to 7.8 over the remaining incubation period. XRD analysis showed that the precipitates were Mg-rich cal- cite (MgxCa(1-x)CO3), whereas no precipitates were formed without the addition of Wu Do-1 in D-1 medium. SEM-EDS analyses showed that the Mg-rich calcite had a rhombohedron shape and consisted of Ca, Si and Mg with an extracelluar polymeric substance (EPS). In addition, TEM-EDS analyses revealed they were hexagon in shape, 500-700 nm in size, and composed of Ca, Mg, C, and O. These results indicated that Wu Do-1 induced precipitation of Mg-rich calcite on the cell walls and EPS via the accumulation of Ca and/or Mg ions. Therefore, microbial precipitation of carbonate nanoparticles may play an important role in metal and carbon biogeochemistry, as well as in carbon sequestration in natural environments.
authors.forename: Ser Ku
authors.initials: SK
authors.lastname: Kang
authors.forename: Yul
authors.initials: Y
authors.lastname: Roh
mesh_terms: D002119:Calcium Carbonate / Q000737:chemistry / Q000378:metabolism; D011232:Chemical Precipitation; D006863:Hydrogen-Ion Concentration; D053758:Nanoparticles / Q000737:chemistry*; D011513:Proteus mirabilis / Q000378:metabolism*
chemical_list: D002119:Calcium Carbonate