Investigation of microbially-mediated carbonate precipitation and incorporation of rare earth elements in mineral precipitates

Abstract

To understand the mechanism of carbonate mineralization by microorganisms is relevant to study the history of Early Earth, such as the formation of microbialites and carbonate deposits in the ocean. But there is still a difficulty in determining the biogenicity of minerals. Dolomite is a carbonate mineral commonly formed at high temperatures abiotically in nature, but there is great difficulty in precipitating this mineral at low temperatures (< 50°C). This carbonate mineral can be precipitated with the activity of halophilic bacteria found in hypersaline lakes, such as in Lagoa Vermelha - Brazil, especially within their exopolymeric substances (EPS). In addition, the history of carbonate precipitation can be reconstructed by the use of rare earth elements (REE), which can enter carbonate lattices by replacing calcium cations. With this in mind, we aim to do experiments regarding the biotic precipitation of carbonates - especially ordered dolomite; evaluate if bioprecipitation of minerals can occur within purified EPS (without viable cells) from halophilic bacteria; and to test if the REE can be incorporated mineral precipitates formed by microbial mats and the bacterial isolates. (AU)