In situ monitoring of exopolymer-dependent Mn mineralization on bacterial surfaces

Thaïs Couasnon (1) , Damien Alloyeau (2) , Bénédicte Ménez (1) , François Guyot (3) , Jean-Marc Ghigo (4) , Alexandre Gélabert (1)

1 IPGP (UMR_7154) - Institut de Physique du Globe de Paris
2 MPQ (UMR_7162) - Laboratoire Matériaux et Phénomènes Quantiques
3 IMPMC - Institut de minéralogie, de physique des matériaux et de cosmochimie
4 Génétique des Biofilms - Genetics of Biofilms

Bacterial biomineralization is a widespread process that affects cycling of metals in the environment. Functionalized bacterial cell surfaces and exopolymers are thought to initiate mineral formation, however, direct evidences are hampered by technical challenges. Here, we present a breakthrough in the use of liquid-cell scanning transmission electron microscopy to observe mineral growth on bacteria and the exopolymers they secrete. Two Escherichia coli mutants producing distinct exopolymers are investigated. We use the incident electron beam to provoke and observe the precipitation of Mn-bearing minerals. Differences in the morphology and distribution of Mn precipitates on the two strains reflect differences in nucleation site density and accessibility. Direct observation under liquid conditions highlights the critical role of bacterial cell surface charges and exopolymer types in metal mineralization. This has strong environmental implications because biofilms structured by exopolymers are widespread in nature and constitute the main form of microbial life on Earth

Domaines: Physique [physics]; Sciences de l'environnement; Chimie

Thaïs Couasnon, Damien Alloyeau, Bénédicte Ménez, François Guyot, Jean-Marc Ghigo, et al.. In situ monitoring of exopolymer-dependent Mn mineralization on bacterial surfaces. Science Advances , 2020, 6 (27), pp.eaaz3125. ⟨10.1126/sciadv.aaz3125⟩. ⟨hal-03099515⟩