Fig 1.
Sampling from icon “The Church Militant” and its surroundings.
Arrows with solid lines indicate sampling from the front (tempera) side and arrows with dotted lines–sampling from the rear side. Sample numbers (1–38) are given in circles. Colors indicate growth on different culture media: yellow, growth only on LB, green–only on CD, red–on both LB and CD, and white–no growth on any.
Table 1.
Phylogenetic analysis of ITS1, 5.8S ribosomal RNA and ITS2 sequences from STG samples.
Fig 2.
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.
Fig 3.
Culture growth on mock layers and biodeterioration dynamics.
Mock layers (indicated on the right) were inoculated with microorganisms (indicated on the top), incubated for 2, 5, or 12 days at 25°C, and analyzed for microbial growth.
Fig 4.
Analysis of biodeterioration in tempera paintings.
(A) Icon “The Church Militant” (object I). (B) Collection of sample 25 from the crack of object I. (C) Sample cultivation on slant CD agar. (D and E) Light microscopy images of sample 25 growth on CD agar (D) and on the surface of mock layer 15 (E); scale bar = 10 μm. (F) Drop and dilution assay for inoculum 25G growth on mock layer 15 (48 h at 25°C). (H and I) Micro-FTIR spectroscopy analysis of biodeterioration in mock layer 15 before (H) and after (I) removal of the 25G-produced microbial sheet. FTIR spectra: 1 –intact levkas, 2 –intact mock layer 15, 3 –periphery of the inoculated zone; 4 –areola zone; 5 –center of the inoculated zone.
Fig 5.
Micro-FTIR spectroscopy of inoculated mock layers.
Analysis was performed for inoculated samples incubated for 12 days at 25°C. (A and B) Mock layer 7 inoculated with sample 106 containing fungus A. amoenus. (C and D) Mock layer 13 inoculated with sample 93W containing fungus A. creber. (A and C) Spectra with microbial sheets. (B and D) Spectra after removal of microbial sheets. 1 –intact levkas, 2 –intact mock layer 15, 3 –periphery of the inoculated zone; 4 –areola zone; 5 –center of the inoculated zone. Absorption peaks: circles–levkas (ground layer), triangles–binder (egg emulsion), squares–fungi.