Barium bioaccumulation by bacterial biofilms and implications for Ba cycling and use of Ba proxies Martínez Ruiz, Francisca Jroundi, Fadwa Paytan, A. Guerra Tschuschke, Isabel Abad Grau, María Del Mar González Muñoz, María Teresa Supplementary Information accompanies this paper at https://doi.org/10.1038/s41467- 018-04069-z. Data availability. The datasets generated during the current study are available from the corresponding author. Ba proxies have been broadly used to reconstruct past oceanic export production. However, the precise mechanisms underlying barite precipitation in undersaturated seawater are not known. The link between bacterial production and particulate Ba in the ocean suggests that bacteria may play a role. Here we show that under experimental conditions marine bacterial biofilms, particularly extracellular polymeric substances (EPS), are capable of bioaccumulating Ba, providing adequate conditions for barite precipitation. An amorphous P-rich phase is formed at the initial stages of Ba bioaccumulation, which evolves into barite crystals. This supports that in high productivity regions where large amounts of organic matter are subjected to bacterial degradation, the abundant EPS would serve to bind the necessary Ba and form nucleation sites leading to barite precipitation. This also provides new insights into barite precipitation and opens an exciting field to explore the role of EPS in mineral precipitation in the ocean. 2018-10-09T09:54:16Z 2018-10-09T09:54:16Z 2018-04-24 info:eu-repo/semantics/article Martínez-Ruiz, Francisca; et. al. Barium bioaccumulation by bacterial biofilms and implications for Ba cycling and use of Ba proxies. Nature Communications (2018) 9:1619 [http://hdl.handle.net/10481/53228] http://hdl.handle.net/10481/53228 10.1038/s41467-018-04069-z eng http://creativecommons.org/licenses/by/3.0/es/ info:eu-repo/semantics/openAccess Atribución 3.0 España Springer Nature