In the presence of cesium carbonate, an efficient synthesis of aryl methyl sulfides by the reactions of aryl halides with commercially available S-methylisothiourea sulfate is developed. This odourless and highly crystalline solid can be used as the substitute for malodorous methanethiol. The gram-scale reaction also proceeds smoothly without the use of column chromatography separation. Similarly, 2-(dimethylamino)ethylthio and cyclopropylmethylthio groups can be easily introduced into the aromatic rings from the corresponding S-[2-(dimethylamino)ethyl]isothiourea dihydrochloride and S-cyclopropylmethylisothiourea hydrobromide. The possible reaction mechanism is proposed. It is believed that this route to aryl alkyl sulfides is well competitive with currently known methods due to its wide substrate scope, excellent yields, easy operation and transition-metal-free conditions.
Significance
The conservation of historical relics against microbial biodeterioration is critical to preserving cultural heritages. One major challenge is our limited understanding of microorganisms’ dispersal, colonization, and persistence on relics after excavation and opening to external environments. Here, we investigate the ecological and physiological profiles of the microbiome within and outside the Dahuting Han Dynasty Tomb with a 1,800-y history. Actinobacteria dominate the microbiome in this tomb. Via interkingdom signaling mutualism, springtails carry Actinobacteria as one possible source into the tomb from surrounding environments. Subsequently, Actinobacteria produce cellulases combined with antimicrobial substances, which helps them to colonize and thrive in the tomb via intrakingdom competition. Our findings unravel the ecology of the microbiomes colonizing historical relics and provide help for conservation practices.
Cultural relics conservation and prevention from bacterial deterioration are critical for our historical heritage. Thus far, the variations of the ecophysiological features of deteriorating bacterial communities along gradients of temperature and moisture remain unclear. In this study, we used high-throughput sequencing to investigate the changing pattern of bacterial communities on bricks at different positions along two such gradients in the Two Mausoleums of the Southern Tang Dynasty, which have more than 1000 years of history. We found that the tombs were inhabited by a phylogenetically and functionally diverse bacterial microbiomes. Herein, Proteobacteria (34.5%), Cyanobacteria (31.3%), Bacteroidetes (7.8%) and Actinobacteria (7.4%), as well as ‘Amino Acid Metabolism (11.2%)’ and ‘Carbohydrate Metabolism (10.5%)’ accounted for the majorities of their compositional and functional profiles related to biodeterioration. Non-metric scaling in combination with PERMANOVA tests indicated that shifts in bacterial community compositions were governed by temperature, followed by moisture. In addition, we found that tourism-related anthropogenic activities could have played non-negligible roles in community assembly, especially in the areas that account as attractions (i.e., back room of the Qinling Mausoleum). Collectively, this study advances the knowledge regarding the deteriorating microbiomes of cultural monuments, which is essential for the conservation of historical cultural relics.
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