Metabolomics and metagenomics analysis of 18th century archaeological silk

The aim of this study was to characterise the microbial and metabolite diversity in samples of biodeteriorated 18th century silk from the burial crypts of the Church of St Francis of Assisi in Krakow (Poland). Highthroughput Illumina sequencing, surface-assisted laser desorption/ionisation mass spectrometry on a silver nanoparticle enhanced target (Ag-109 SALDI), and laser ablation-remote-electrospray ionisation-selected reaction monitoring-ambient mass spectrometry imaging (LARESI MSI) were employed. The use of high throughput Illumina sequencing helped obtain a broader picture of microbiocenosis compared to earlier studies. The Ag-109 SALDI method enabled the qualitative analysis of the entire chemical compound profile of silk. A few hundred metabolites, including peptides, amino acids, urea and organic acids dominated by N-(3-oxododecanoyl)-L-homoserine, decanoylcholine, formiminoalanine and hexacosatrienoic acid were detected in archaeological silk, whereas about 100 metabolites, mainly represented by polymers, were detected in contemporary and restored silk. The novel ambient MS imaging method LARESI MSI, used for the first time for the archaeological silk biodeterioration analysis, allowed the direct detection and mapping of selected amino acids, historical dyes and dihydroxybenzoic acid (decomposition product of tannins) on the silk samples. Based on our results, the suitability of the tested methods should also be considered for other historical objects.

Automated summary

This study aimed to characterize microbial and metabolite diversity in biodeteriorated 18th century silk samples using high-tech methods. Archaeological silk had hundreds of metabolites including peptides and amino acids, while contemporary and restored silk mainly consisted of polymers. The novel analysis methods could be applicable to other historical objects.