No abstract

Cave air, bat guano, and swabs of bat fur from caves with bat guano in Romania were analyzed by using RIDAHCOUNT cultivation plates and standard selective media for Staphylococcus and Streptococcus. 7 CFU/g). The gravity-settling principle was applied to sample airborne microorganisms, and a new method was developed for evaluation of aerosolization potential. In cave air, the concentration of total bacteria was higher than yeast and molds. In addition to coliforms, enterobacteria, E. coli, and unidentified cultivable bacteria in the air samples, we also identified Chryseomonas luteola, Klebsiella pneumoniae, Micrococcus, Salmonella, Staphylococcus, and Streptococcus. In the experiment that provoked microbial aerosolization from guano, 3.35% of total cultivable fungi were aerosolized, up to 0.10% of bacteria, and 0.00% of E. coli. The concentration of Staphylococcus in the air exceeded counts of Streptococcus. The highest concentrations of airborne microorganisms were on the ground level. Using cultivation plates as a robust method we demonstrated that the relative proportion of microbial subgroups in the air remained constant in different seasons, with lower concentrations of airborne microbiota in the autumn. Caves as simplified natural systems demonstrated complex relationships between atmospheric parameters and microorganisms. Bats introduce into caves varying, but not negligible, concentrations of microbes on their fur. Caves with guano had relative high concentration of airborne microbes that may represent a biohazard for animals and humans.

No abstract

The human impact upon the subterranean microbiomes is not only a peril to the cave environment but might also affect future visitors. We focused on the changes that humans induced on the surfaces they came in direct or indirect contact with inside two intensely visited Romanian show caves, by means of commercially available microbial rapid test kits and molecular identification. Overall culturable bacteria abundance in the caves maintained high levels year-round while Enterobacteriaceae, coliform bacteria and Escherichiacoli levels peaked during the touristic season, reaching levels that could pose a threat to the health of the visitors. Culturable fungi abundance usually peaked in the spring, remained at a high level in the summer and started to slowly decrease towards the winter months. Differences were observed between the direct and indirect exposed surfaces, as the later had lower overall levels of bacteria and fungi, with increased Enterobacteriaceae loads. Most of the taxa identified are known biodeteriorants of subterranean surfaces and were previously associated with human altered caves. A Dothideomycete sp. previously unknown to the cave environments was detected. This was the first study to analyse the dynamics of the microbial communities of delicate subterranean surfaces in show caves through the use of commercially available test kits. We revealed that exposed surfaces in show caves, in direct or indirect contact with tourists, are host to high concentrations of cultivable microbes. The touristic activity was shown to influence the abundance and dynamics of the microbial communities inhabiting surfaces of show caves.