Community structure and functions of bacteria in ivory unearthed from Sanxingdui ruins
To assess the potential of microorganisms to induce damage to ivory excavated from the Sanxingdui Site,we analyzed the structures and functional characteristics of bacterial communities in ivory recovered from an archaeological pit at the site.Scanning electron microscopy-energy spectroscopy and inductively coupled plasma mass spectrometry were used to observe and analyze the morphology and elemental composition of the excavated ivory.The bacterial community composition was determined using culture-based techniques and high-throughput sequencing.The results showed that:(1)Surface examination revealed conspicuous cracks on the excavated ivory,resembling carbonized wood in morphology and structure,with evident microbial colonization and poor preservation conditions.(2)High-throughput sequencing revealed a rich bacterial diversity in the excavated ivory,predominantly comprising Proteobacteria,Acidobacteria,Bacteroidetes,Firmicutes,Actinobacteria,Chloroflexi,Nitrospirae,Candidatus Saccharibacteria,Verrucomicrobia,and Planctomycetes,with Acidobacteria and Proteobacteria being the dominant phyla.(3)Significant variation in the composition and abundance of dominant bacteria among ivory excavated from different burial pits was observed,with greater uniformity within the no.5 burial pit.(4)Correlation analysis demonstrated that heavy metal types and contents(Cu,Cr,Mn,Ni,and Pb)were associated with the bacterial community structure within the ivory samples.(5)Functional prediction highlighted the dominant metabolic pathways within the unearthed ivory:metabolism of cofactors and vitamins,amino acid metabolism,carbohydrate metabolism,and metabolism of terpenoids and polyketides.(6)Culture-based techniques yielded 16 culturable bacterial species from the ivory,spanning four phyla and 13 genera.(7)Acid-production and copper-resistance experiments revealed that the 10 tested strains possessed acid-producing abilities and exhibited varying tolerances to CuSO4(ranging from 500 to 1 000 mg/L),posing potential harm to the ivory.This study elucidated the richness of bacterial species in Sanxingdui-excavated ivory,highlighting the potentially damaging bacterial groups that threaten ivory preservation.These findings serve as a scientific foundation for safeguarding the unearthed ivory from the Sanxingdui ruins.
Sanxingdui ruinsunearthed ivorybacterial community structurebacterial function
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