Barite, a mineral compound of barium, is now a direct and accurate proxy for marine productivity, marine climate, and marine life evolution in general
Researchers from UGR and CSIC have discovered the mechanism by which the extracellular polymeric substances produced by different marine bacteria are responsible of barium bioaccumulation, thus explaining barite precipitation
Barite, a mineral compound of barium, is now a direct and accurate proxy for marine productivity, marine climate, and marine life evolution in general. However, the biogeochemical cycle of barium, which is closely related to the carbon cycle, is not well constrained, being a mystery how barium precipitates in ocean waters. In fact, barite precipitation in seawater, undersaturated with respect to barium, has puzzled the scientific community for decades.
Now, a study carried out by researchers from the University of Granada (UGR) and the Spanish National Research Council (CSIC, from its name in Spanish) has proven that bacteria may play a crucial role in barite precipitation. The results have been published in Nature Communications.
“Experiments carried out with diverse marine bacteria shed light on the processes by which barite precipitates in bacterial biofilms from the bioaccumulation of barium in bacterial cells and extracellular polymeric substances (EPS)”, Francisca Martínez Ruiz and María Teresa González Muñoz, researcher from the Andalusian Earth Sciences Institute (IACT) and professor emeritus of the Department of Microbiology at the UGR, respectively, explain. Both women are co‑authors on this paper.
“The results of this experimental study support the hypothesis that during periods of high productivity, large amounts of organic matter subjected to bacterial degradation along with the production of extracellular polymeric substances lead to barium accumulation”, they add.
At the initial stages of barium bioaccumulation this element binds to phosphate groups present in EPS, thus forming an amorphous precursor which later evolves to barium sulfate (barite crystals) after replacing phosphate groups with sulfate groups. The study of barite from water columns in areas of high productivity also proves the existence of a P‑rich amorphous precursor. “This finding therefore opens a novel field of the greatest interest, about microbial precipitation in seawater and the role of extracellular polymeric substances in mineral precipitation and the absorption of diverse metals. This would play a crucial role in a large number of biogeochemical cycles”, the researchers conclude.
This study was supported by the European Regional Development Fund (ERDF) co‑financed grant CGL2015‑66830‑R (MINECO Secretaría de Estado de Investigación, Desarrollo e Innovación, Spain), Research Groups BIO 103 and RNM‑179 (Junta de Andalucía), and the University of Granada (Unidad Científica de Excelencia UCE‑PP2016‑05).
Bibliographic references:
- Francisca Martinez‑Ruiz, Fadwa Jroundi, Adina Paytan, Isabel Guerra‑Tschuschke, María del Mar Abad & María Teresa González‑Muñoz. Barium bioaccumulation by bacterial biofilms and implications for Ba cycling and use of Ba proxies. Nature Communications.
DOI: 10.1038/s41467-018-04069-z
Biofilm produced by one of the bacterial strains used in this experimental work (image obtained by HRSEM at the Center for Scientific Instrumentation [CIC‑UGR]).
Contact info:
María Teresa González Muñoz
Department of Microbiology, Faculty of Science, University of Granada
Phone number: (+34) 958 24 28 58
E‑mail: mgonzale@ugr.es
Francisca Martínez Ruiz
Andalusian Earth Sciences Institute (CSIC‑UGR)
Phone number: (+34) 958 23 00 00 ext. 190218
E‑mail: fmruiz@ugr.es
