Evolutionary investigation of the biomineralization of dolomite by EPS-forming bacteria from Lagoa Vermelha in Rio de Janeiro, Brazil

Abstract

The precipitation of dolomite in the Earth's modern sedimentary environments occurs, for the most part, mediated by microorganisms. The way in which bacteria are capable of facilitating or inducing mineral precipitation has not yet been fully elucidated. However, it is known that extracellular polymeric substances (EPS) secreted by bacteria facilitate the mineral nucleation and precipitation by creating an ideal physico-chemical environment for mineral formation, in this case, of dolomite. The secretion of EPS is widespread among microorganisms and can perform several different roles, including a common mechanism for protecting extremophiles from adverse conditions. In the present project, the bacterial capability of bioprecipitation of dolomite, using EPS-secreting bacterial isolates from a hypersaline lagoon will be investigated by combining microbiological, microscopic and geochemical analytical techniques. The isolates will be evaluated for their ability to produce bioprecipitates, especially dolomite, to be studied by analytical techniques as X-ray diffractometer (XRD) and scanning electron microscope (SEM). This research study will be conducted at the Vrije Universiteit Amsterdam (VUA) in The Netherlands, and daily supervised by Professor Dr. Mónica Sánchez-Román. Afterwards, the obtained data at the VUA will be carried out at the CNPEM in Brazil, where will use analytical techniques as micro-Raman spectrometry, X-ray fluorescence (XRF) and X-ray diffraction (XRD) in LNLS. In Brazil, the isolates will be submitted to different environmental simulations, varying environmental UV radiation and salinity, so the resulting samples will be analyzed to evaluate the survival of the colonies according to the different radiation parameters by counting colony forming units (CFU). In this way, it will be possible to verify if bacteria capable of precipitation of biominerals, like dolomite, are more tolerant to conditions of extreme environments, like ultraviolet radiation, in relation to the others that live in the same environment of Lagoa Vermelha. This study will represent a major step towards understanding the biomineralization phenomenon occurring in extreme environments since a geomicrobiological and biogechemical perspective. (AU)