Investigation of microbial mechanisms in carbonate bioprecipitation processes

• Grant number: 21/08191-6
• Support Opportunities: Scholarships in Brazil - Doctorate (Direct)
• Start date: December 01, 2021
• End date: October 31, 2027
• Field of knowledge: Physical Sciences and Mathematics - Geosciences
• Principal Investigator: Douglas Galante
• Grantee: Fernanda Salles Jamel
• Host Institution: Instituto de Geociências (IGC). Universidade de São Paulo (USP). São Paulo , SP, Brazil
• Associated research grant: 16/06114-6 - The Neoproterozoic Earth System and the rise of biological complexity, AP.TEM
• Associated scholarship(s): 22/14929-0 - Investigation of microbially-mediated carbonate precipitation and incorporation of rare earth elements in mineral precipitates, BE.EP.DD

Abstract

The precipitation of carbonates by microorganisms has been studied for several applications, such as understanding the environment of pre-salt reserves where microbialites are found and, more recently, to help detect life on other planets and planetary objects. In the latter case, there is a difficulty in identifying biosignatures related to the determination of biogenicity, that is, confirmation that the compound found would be of biological origin. Dolomite is commonly formed abiotically at high temperatures in nature, but there is great difficulty in precipitating this mineral at low temperatures (< 50°C). This carbonate mineral can be precipitated with the action of halophilic bacteria found in hypersaline lakes, such as Lagoa Vermelha, in Araruama - RJ. Carbonate precipitating microorganisms have also been targeted for biomining activities, as some species are capable of mobilizing elements of great economic importance, such as rare earth ions. This application can even be used on other planetary bodies, such as the Moon and Mars. In addition, rare earth ions have applications in luminescence and can be used to assist instruments such as rovers in detecting off-planet biosignatures. With this, the present project aims to analyze the biotic and abiotic precipitation of carbonates, especially dolomite, to identify characteristics related to the biogenicity of these compounds and assist in the identification criteria for mineral biosignatures. Through synchrotron light techniques, such as X-Ray Diffraction and Absorption (XRD and XAS) and X-ray Excited Optical Luminescence (XEOL) it will be possible to analyze the micro-mineral precipitates at the nanoscale. The biotic mineral precipitates will be obtained through experiments involving the presence of exopolysaccharides (EPS) produced by isolated bacteria. The formation of these minerals will be tested under different conditions such as temperature, high salinity and UVC radiation, and the preservation of potential biosignatures will be tested in environmental simulations of the Noachian period of Mars and the Neoproterozoic of Earth. At the end of the project, it is expected to find biological precipitates of dolomite and other carbonates in the different environmental conditions tested; and furthermore, it is expected to obtain little or no difference in the precipitate submitted to Martian and terrestrial simulation in past geological periods, compared to the precipitate obtained under current atmospheric conditions; and evaluate possible structural, optical and morphological differences of biotic and abiotic precipitates. As a contribution, it is expected to apply the knowledge obtained in the development of new methodologies for imaging bioprecipitated structures, expand the knowledge of the mechanism of bioprecipitation of minerals and help the recognition of biosignatures by space mission instruments such as rovers. (AU)