Fig. 6.

Analysis of in situ bio-treated calcarenite stone. SEM images of untreated calcarenite (a) and calcarenite treated with the bacterial community (b–e). a Micrometer-sized calcite (Cc) crystals in the control stone show dissolution pits and are covered by salt (e.g., NaCl) crystals; b bacterial calcite (BCc) cement shows nanogranular structure surrounded by EPS; c detail of the nanogranular structure of calcite biocement interspersed with EPS; d bacterial calcite and abundant EPS covering the calcarenite substrate; e detail of mineralized bacterial cells (arrows); f XRD patterns of calcarenite before (blue) and after (red) bacterial bio-treatment. Cc, calcite; Gy, gypsum; Qtz, quartz