Spatial and temporal distribution characteristics of the airborne bacteria in the Maijishan grottoes, China

Abstract:

[Objective] The deposition of the airborne microorganisms and air pollution were closely related to the biodeterioration of the cultural heritage. In this study, a systematic survey of seasonal variation characteristics of bacterial concentration and community structure was carried out in the surrounding atmosphere of Maijishan Grottoes, a renowned cultural heritage site in China. The results will be helpful for the environmental monitoring and precaution of cave temples and preventive protection of cultural relics. [Methods] The Bio-aerosol sampler was used for sampling in all seasons in 2016. Traditional culture-based method to acquire the airborne bacterial concentration information and purified strains; by the extraction of genomic DNA, amplification of bacteria 16S rRNA region, sequencing, and phylogenetic analysis, thereafter the bacteria community composition and distribution characteristics were clarified. Combined with environmental monitoring data, to find out the main factors which may responsible for the dynamic changes of the airborne bacteria. [Results] The concentrations of culturable bacteria were in a range from 281.2 to 1409.2 CFU/m³, the highest and the lowest concentration appears at MJ4 in summer and at MJO in spring, which varied apparently with seasonal characteristics, but no significant difference among different sites. A total of 11 different bacterial genera that affiliated to four phyla were detected in this study, among which, Bacillus, Paenarthrobacter, Arthrobacter, Hymenobacter and Kocuria were dominant genera. [Conclusion] The airborne bacterial community structures of the Maijishan grottoes show a dynamic characteristic of the seasonal variation and spatial distribution; RH, temperature and rainfall all have influenced on the airborne bacteria distribution in different layers of the Grottoes; some of the genus, such as Bacillus and Micrococcus, has potentials that could result in the biodeterioration of the ancient wall paintings and painted sculptures at this site; the monitoring of the airborne bacteria in its surrounding atmosphere of the Maijishan grottoes may contribute to the grottoes conservation and tourism management.

Key words:Cave temples;airborne bacteria;community composition;spatial-temporal variation;monitoring and precaution