HIGH PHYLOGENETIC DIVERSITY OF BACTERIA IN THE AREA OF PREHISTORIC PAINTINGS IN MAGURA CAVE, BULGARIA

Magura Cave, situated in the northwest of Bulgaria and containing prehistoric paintings, is a famous tourist site. The present study is the first report on bacterial diversity in guano paintings in a Bulgarian cave using molecular methods. We identified 68 taxa, which is an unusually high number for oligotrophic niches. They are affiliated with eight phyla representing more than half of the bacterial divisions identified in caves. As in many other caves, Proteobacteria dominated in this type of ecosystem (about 40%), followed by Nitrospirae (22.5%) and Acidobacteria (21.5%). Weakly represented were Actinobacteria (6.4%), Chloroflexi (3.2%), Planctomycetes (2.2%), Firmicutes (2.2%), and Gemmatimonadetes (2.2%). About one third of all DNA sequences recovered in this study were new. Some of them had more than 10% divergence from the closest neighbor, which suggests the existence of new taxa of at least genus level. Bacteria identified in the community expressed various types of metabolism; lithoautotrophic, organotrophic, and methylotrophic.