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. 2020 Dec 16;8(12):2015.
doi: 10.3390/microorganisms8122015.

Essential Oils as Alternative Biocides for the Preservation of Waterlogged Archaeological Wood

Federica Antonelli  1 , Marco Bartolini  2 , Marie-Laure Plissonnier  3 , Alfonso Esposito  4 , Giulia Galotta  2 , Sandra Ricci  2 , Barbara Davidde Petriaggi  5 , Cristian Pedone  6 , Antonella Di Giovanni  6 , Silvano Piazza  4   7 , Francesca Guerrieri  3 , Manuela Romagnoli  1
Affiliations

Essential Oils as Alternative Biocides for the Preservation of Waterlogged Archaeological Wood

Federica Antonelli et al. Microorganisms. .

Abstract

Waterlogged archaeological wood is exposed to a high risk of biological degradation during the post-excavation phases of storage and restoration. For this reason, often biocides must be used to preserve wooden remains. In the present work three essential oils (cinnamon, wild thyme, and common thyme) were tested as possible alternative biocides to use in the preservation of waterlogged archaeological wood. The oils were first tested in vitro to establish the minimum inhibitory concentration (MIC) and to evaluate the biocidal activity on selected fungal strains. Then, the established MIC was applied on waterlogged archaeological wood samples and during an actual restoration treatment. The effectiveness of the oils was evaluated through cultural analyses, ATP quantification, and next-generation sequencing. The results showed that the oils caused a significant decrease in the vitality of fungal mycelia grown in vitro and of the microbiota present in treated wood and storage water. Furthermore, an influence on the composition of the bacterial communities of treated wood samples was observed. Although further tests are needed to evaluate interferences with the materials used during restoration procedures, essential oils could be considered as a possible alternative to the currently used biocide.

Keywords: ATP bioluminescence; NGS; WAW; archaeological wood biodegradation; archaeological wood restoration; cinnamon; common thyme; cultural analyses; minimum inhibitory concentration (MIC); wild thyme.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Results of cultural tests carried out on the fungal mycelia treated with the EOs MIC. (C: cinnamon; WT: wild thyme; CT: common thyme; WE: water-ethanol).
Figure 2
Figure 2
Stacked barcharts showing the relative abundance of bacterial phyla (a) and families (b) in each sample. Tips of the clustering tree are colored according to the treatments. (C: cinnamon; E: ethanol; CT: common thyme; NT: not-treated control; WT: wild thyme).
Figure 3
Figure 3
Boxplots showing the relative abundance of selected bacterial taxa identified as biomarkers in the LEfSe analysis. (C: cinnamon; E: ethanol; CT: common thyme; NT: not-treated control; WT: wild thyme).
Figure 4
Figure 4
Taxa identified as biomarkers for each treatment by LEfSe analysis, LDA scores (log10) threshold was set to 3. (C: cinnamon; E: ethanol; CT: common thyme; NT: not-treated control; WT: wild thyme).
Figure 5
Figure 5
Stacked barcharts showing the relative abundance of fungal phyla (a) and species (b) in each sample. Tips of the clustering tree are colored according to the treatments. (C: cinnamon; E: ethanol; CT: common thyme; NT: not-treated control; WT: wild thyme).
Figure 6
Figure 6
Boxplots showing the relative abundance of selected fungal taxa identified as biomarkers in the LEfSe analysis. (C: cinnamon; E: ethanol; CT: common thyme; NT: not-treated control; WT: wild thyme).
Figure 7
Figure 7
Boxplots of alpha-diversity index (calculated as Shannon index) (a) 16S. (b) ITS. (C: cinnamon; E: ethanol; CT: common thyme; NT: not-treated control; WT: wild thyme).
Figure 8
Figure 8
Principal component analysis calculated on the 16S (a) and ITS (b) ecological matrices at the level of OTU. (C: cinnamon; E: ethanol; CT: common thyme; NT: not-treated control; WT: wild thyme).
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References

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