Bacteria consortia and deterioration of archaeological waterlogged wood: identification by molecular and microscopy techniques

Abstract

In this study molecular tools are applied to reveal and identify bacterial colonization in waterlogged wood to assessing the changes induced in anatomical structure, previously observed by Optical and Scanning Electron Microscopy (1). The results obtained by observation of wooden thin sections (OM), shown the presence of black and dark-brown areas and mineral concretions. The SEM analysis revealed a specific cell walls alteration, attributable to bacterial activity, other than abundant pyrite framboids (FeS2). The presence of sulfur compounds in archaeological waterlogged wood can indicate both long-term burial in anoxic environment and colonization by sulfate-reducing bacteria. Molecular methods allow us extract microbial genomic DNA from wood samples and in vitro amplify (PCR) bacteria DNA target sequences (16S, ITS-rRNA) (2). Through sequences analysis of PCR products cellulosolytic and ligninolytic bacteria, such as Pseudomonas, Cellulomonas, Xanthomonas and Bacillus spp, have been revealed. Moreover the presence of Marinobacter sp. and Desulforudis audaxviator, respectively iron-oxidizing and sulfate-reducing bacteria, are identify. We hypothesize that this investigation approach, can be applied to a variety of wooden artifacts of archaeological findings for both characterization of microbial colonization in order to understanding the main degradation phenomena, indispensable for a correct conservation strategies. (1) Safa A. et al. (2012) Using SEM in monitoring changes in archaeological wood: A review. Current Microscopy Contributions to Advances in Science and Technology (A. Méndez-Vilas, Ed.) (2) Palla, F., (2012) Analytical techniques: analysis of microbial colonization. In Science and Conservation in Museum Collections, B. Fabbri (ed), Nardini, Firenze. 14, 459-470.