Bacteria in drinking and bathing mineral waters of Serbia with polymer-degrading potential

Abstract

Three mineral water occurrences, captured by wells with a depth of 6.5-442.5 m and used for drinking and bathing purposes, were sampled and cultivated under conditions favouring the growth of anaerobic, microaerophilic or CO2 bacteria, in order to capture predominantly anaerobic portion of the bacteriome, which is dominant in water and soils. Cultivated bacteria were identified by next-generation 16S sequencing and their biotechnological potential in plastics and lignocellulose degradation was explored. Most abundant genera detected in examined samples mainly belong to facultative anaerobes that are common representatives of water and soil environments. In total, 17 genera were detected with a relative abundance over 1% in all three samples, including Aeromonas, Exiguobacterium, Comamonas and Acinetobacter. Half of the screened isolates demonstrated growth on at least one plastic or lignocellulosic polymer, with one isolate demonstrating growth on all tested substrates, one demonstrating carboxymethyl cellulose- and one arabinoxylan-degrading ability. Some of the representatives of genera identified with high relative abundance in mineral water samples, such as Aeromonas, Klebsiella, Escherichia, Salmonella, Enterobacter, Pseudomonas and Staphylococcus, have been previously documented to have pathogenic potential. Due to the use of investigated mineral waters for drinking and bathing, the health risk from such bacteria in these occurrences needs to be continuously monitored, while, on the other hand, mineral waters deserve special attention in the future from the aspect of screening for biotechnologically relevant enzymes.