Studies On Microbial Contaminations Of Waterlogged Wooden Relics

Wooden relics are not only a carrier of ancient civilization,but also valuable materials for studying ancient history,art,science and technology,and economy.However,due to environmental and human factors,lots of wooden cultural heritages are being colonized and degraded by microorganisms.In this study,two waterlogged wooden relics—Nanhai No.1 shipwreck and Dingtao M2 huangchang ticou tomb presented visible microbial contamination.By using a combination of culture-independent and culture-dependent methods,the aim of our study was(i)to investigate microbial communities responsible for the biodeterioration of the two relics;(ii)to study the characteristics of main microorganisms;(iii)to mitigate current microbial deterioration.According to the field investigation and microscopic observation,it was found that microbial contamination of the Nanhai No.1 shipwreck was mainly fungi.16S amplicon sequencing revealed that bacterial communities were dominated by Firmicutes and Proteobacteria,while fungi,represented by Fusarium solani,predominated in six samples;Two strains Fusarium sp.NK-NH1 and Fusarium sp.NK-NH2 were isolated and identified by molecular methods and phylogenetic analysis.Both of them had the capability to degrade lignin or cellulose,which should be regarded as posing a threat to the long conservation of the ship.In addition,the borate buffer solution(BBS)which has been used to prevent microbial colonization couldn't inhibit the growth of isolated Fusarium,while other biocides including the Preventol~?D 7,P91,BIT 20N and Euxyl~?K100 had effectiveness against the growth of Fusrium species in the laboratory conditions.According to this result,the K100 was selected to control current fungal deterioration and obtained the good effect.Fungal contamination of M2 huangchang ticou tomb was more serious than Nanhai No.1 shipwreck.The white spots have spread to every chamber.ITS amplicon sequencing documented Hypochnicium was the most abundant genus across six samples and accounted for 98.61%to 99.45%of the total community composition.Further,Hypochnicium sp.and Mortierella sp.cultures were successfully isolated from the tomb samples,and were distinguished as Hypochnicium sp.WY-DT1 and Mortierella sp.NK-DT1,respectively.In cooperation with Chinese Academy of Cultural Heritage(CACH),two kinds of physical methods including ironing and oxygen insulation were applied to mitigate biodeterioration and achieved good effect.In addition,the archaeological workers were required to wear a sterile protective clothing and boots to enter the tomb M2 in order to prevent the new microorganism's entrance.