Characterization of mock layer models using micro-FTIR spectroscopy.

(A) FTIR absorption spectra for intact mock layers. (B)–(E) Modeling of sturgeon glue biodeterioration with cultured isolate 93B (containing C. parahalotolerans). Light microscopy analysis of inoculum 93B; scale bar = 10 μm (B). Spectral properties of sampling zones: 1, 2 –intact zones; 1', 2'–periphery of the inoculated zone (according to the growth on mock layer 1); 1'', 2''–center of the inoculated zone (C–E). Visible biodeterioration of mock layers 1, 2 with inoculum 93B after 12 days at 25°C (C, D). FTIR spectra revealing biodeterioration (E). Levkas, 0; glues: 1, 2 –sturgeon glue without and with 1% SPCP, respectively; plasticizers: 6 –gum arabic, 9 –rosin; tempera paints: 7 –egg emulsion, 14 –egg tempera with ochre, 15 –egg tempera with cinnabar, 20 –egg manufacturing tempera “Rowney” (Monestial Blue Phthalo); varnishes: 10 –wax-oil mastic, 13 –Dammar varnish (see also S1 Table). Colors of spectra for tempera mock layers (7, 14, 15, and 20) correspond to those of the layers.