Protection and consolidation of stone heritage by self-inoculation with indigenous carbonatogenic bacterial communities

Enhanced salt weathering resulting from global warming and increasing environmental pollution is endangering the survival of stone monuments and artworks. To mitigate the effects of these deleterious processes, numerous conservation treatments have been applied that, however, show limited efficacy. Here we present a novel, environmentally friendly, bacterial self-inoculation approach for the conservation of stone, based on the isolation of an indigenous community of carbonatogenic bacteria from salt damaged stone, followed by their culture and re-application back onto the same stone. This method results in an effective consolidation and protection due to the formation of an abundant and exceptionally strong hybrid cement consisting of nanostructured bacterial CaCO3 and bacterially derived organics, and the passivating effect of bacterial exopolymeric substances (EPS) covering the substrate. The fact that the isolated and identified bacterial community is common to many stone artworks may enable worldwide application of this novel conservation methodology.This work was supported by the Spanish Government (Grants MAT2012-37584, CGL2012-35992 and CGL2015-70642-R), the Junta de Andalucía through Proyecto de excelencia RNM-3493 and Project P11-RNM-7550, the Research Groups BIO 103 and RNM-179, and the University of Granada (Unidad Científica de Excelencia UCE-PP2016-05). Additional funds were provided by the Molecular Foundry (Lawrence Berkeley National Laboratory, LBNL, University of California, Berkeley, CA) for a research stay of M.S. (project #1451; User Agreement No. NPUSR009206)