Seasonal variations of airborne bacteria in the Mogao Grottoes, Dunhuang, China

Airborne bacteria are important biological components of bioaerosol and play an important role in the conservation of cultural heritage. High concentration of bacteria in the atmosphere can result in biological air pollution and potentially diseases. In this study, a systematical survey of culturable airborne bacteria was carried out in Mogao Grottoes of Dunhuang, China at four sites (one cave is open to visitors, another is semi-closed, the third one is closed to visitors, and the fourth site is the entrance gate). Airborne bacteria were collected using a six-stage culturable FA-1 sampler monthly from September 2008 to August 2009. The populations of culturable bacteria were in a range from 1.01 × 102 colony forming units (CFU/m3) to 3.8 × 103 CFU/m3. The mean was 1.30 × 103 ± 145 CFU/m3, 1.1 × 103 ± 279 CFU/m3, 4.4 × 102 ± 67 CFU/m3 and 4.4 × 102 ± 77 CFU/m3 in the Closed Cave, Open Cave, Semi-closed Cave and the Entrance, respectively. The particle size of airborne bacteria were mainly distributed in stage 4 of sampling with diameters approximately 2.1–3.3 μm. The correlation was found between airborne bacterial concentrations and environmental temperature, relative humidity, as well as tourists number. The results suggested that the number of visitors has an obvious influence on both the concentrations and the compositions of ambient bacteria in Mogao Grottoes

Molecular characterization of airborne fungi in caves of the Mogao Grottoes, Dunhuang, China

In this study, we analyzed air samples collected from several sites within the Mogao Grottoes, Dunhuang, China. The samples were collected each month from September 2008 to August 2009 from an open cave (OC), a semi-open cave (SC), a closed cave (CC), and the entrance (EN) of the Mogao Grottoes. Sampling was carried out using a six-stage Andersen FA-I sampler; then samples were cultured and fungal isolates were identified by partial sequencing of their internal transcribed spacer (ITS) region. Eleven different fungal genera were found, and the most prevalent was Cladosporium, followed by Fusarium, Penicillium, Alternaria, and Aspergillus. The fungal community composition varied among the four sites. Fungal community structure was significantly related to site (r = −0.293, p = 0.039) and to time of year (r = −0.523, p = 0.000). The concentrations and abundance of airborne fungi varied greatly throughout the year at the four sampling sites. Meteorological parameters (e.g., temperature, relative humidity) and the number of visitors also influenced both abundance and community structure of airborne fungi in the Mogao Grottoes

Correction: The microbial community characteristics of ancient painted sculptures in Maijishan Grottoes, China.

[This corrects the article DOI: 10.1371/journal.pone.0179718.]

Diversity and Composition of Culturable Microorganisms and Their Biodeterioration Potentials in the Sandstone of Beishiku Temple, China

Microbial colonization on stone monuments leads to subsequent biodeterioration; determining the microbe diversity, compositions, and metabolic capacities is essential for understanding biodeterioration mechanisms and undertaking heritage management. Here, samples of epilithic biofilm and naturally weathered and exfoliated sandstone particles from different locations at the Beishiku Temple were collected to investigate bacterial and fungal community diversity and structure using a culture-based method. The biodeterioration potential of isolated fungal strains was analyzed in terms of pigmentation, calcite dissolution, organic acids, biomineralization ability, and biocide susceptibility. The results showed that the diversities and communities of bacteria and fungi differed for the different sample types from different locations. The population of culturable microorganisms in biofilm samples was more abundant than that present in the samples exposed to natural weathering. The environmental temperature, relative humidity, and pH were closely related to the variation in and distribution of microbial communities. Fungal biodeterioration tests showed that isolated strains four and five were pigment producers and capable of dissolving carbonates, respectively. Their biomineralization through the precipitation of calcium oxalate and calcite carbonate could be potentially applied as a biotechnology for stone heritage consolidation and the mitigation of weathering for monuments. This study adds to our understanding of culturable microbial communities and the bioprotection potential of fungal biomineralization

The microbial community characteristics of ancient painted sculptures in Maijishan Grottoes, China

<div><p>In this study, a culture-independent Illumina MiSeq sequencing strategy was applied to investigate the microbial communities colonizing the ancient painted sculptures of the Maijishan Grottoes, a famous World Cultural Heritage site listed by UNESCO in China. Four mixed samples were collected from Cave 4–4 of the Maijishan Grottoes, the so-called Upper Seven Buddha Pavilion, which was built during the Northern Zhou Dynasty (557-581AD). The 16/18S rRNA gene-based sequences revealed a rich bacterial diversity and a relatively low fungal abundance, including the bacterial groups Actinobacteria, Acidobacteria, Bacteroidetes, Cyanobacteria, Chloroflexi, Firmicutes, Proteobacteria and Verrucomicrobia and the fungal groups Ascomycota, Basidiomycota and Chytridiomycota. Among them, the bacteria genera of <i>Pseudonocardia</i> and <i>Rubrobacter</i> and unclassified fungi in the order of Capnodiales were dominant. The relative abundance of <i>Pseudonocardia</i> in the painted layer samples was higher than that in the dust sample, while Cyanobacteria dominated in the dust sample. Many of them have been discovered at other cultural heritage sites and associated with the biodeterioration of cultural relics. The presence and activity of these pioneering microorganisms may lead to an unexpected deterioration of the painted sculptures that are preserved in this heritage site. Thus, proper management strategies and potential risk monitoring should be used in the Maijishan Grottoes to improve the conservation of these precious painted sculptures.</p></div

Shared OTU analysis of the different samples.

<p>Venn diagram showing the unique and shared OTUs (97%) for the bacterial (A) and fungal (B) communities among the four samples.</p

Heat map representation and cluster analysis of the microbial community among four samples.

<p>Bacterial (A) and fungal (B) distributions of the top 50 abundant genera and families, respectively. The double hierarchical dendrogram shows the bacterial and fungal distribution. The bacterial and fungal phylogenetic trees were calculated using the neighbor-joining method.</p

Relative abundance of the fungal community at the family level.

<p>Relative abundance of the fungal community at the family level.</p

Principal components analysis.

<p>Scatter plot of the PCA-score showing the similarity of the bacterial (A) and fungal (B) communities based on the Unifrac distance.</p