EXOpolymeric substances as catalyzers of DIAgenetic reactions: implications for metal accumulation in modern and ancient estuaries

The first objective of EXODIA is to understand microbial metabolisms related to EPS turnover in estuarine sediments. The second objective is to isolate and cultivate EPS producers and degraders from key sedimentary and/or geochemical interface. The third objective is to analyze the capacity of EPS extracted from sediments and of EPS produced in culture to form complexes with metals, ultimately leading to their precipitation. The fourth objective is to characterize the transformations of EPS and minerals (precipitation vs. dissolution) in forced diagenesis experiments reproducing the conditions encountered by the sediment during burial in a sedimentary basin. The fifth objective is to search for biosignatures of EPS-metal interactions in a collection of ancient estuarine sandstones of increasing age, burial and diagenesis. In ancient sandstones, we have documented several early diagenetic mineral phases, which could have precipitated following EPS-mineral-porewater reactions.