Exploring Cultivable Stress-Tolerant Bacteria in the Skin of Speleomantes italicus

The skin microbiota protects organisms from external agents and environmental stress rising due to anthropogenic activities and climate change. As part of projectFFORIC24.35, we aim to characterize the skin microbiota of European plethodontid salamanders (genus Speleomantes), a group of eight strictly protected species that are either endemic or sub-endemic in Italy. The present study focused on the cultivable bacterial communities associated with individuals from a cave population of S. italicus from Abruzzo region. The cultivable microbiota of twelve individuals was sampled and isolated using the Nutrient Agar medium by swabbing the collected samples on plates and then incubating them at 29°C for 48 hours. After purification, we characterized the bacterial isolated strains based on morphological traits and bacteriological classifications. Each strain was also tested for heavy metal stress, drought tolerance, and exopolysaccharides (EPS) production. The isolates with interesting characteristics were identified using DNA barcoding and phylogenetic analysis. The isolation yielded seventeen strains, the majority of which being classified under the Actinobacteria and Firmicutes. Interesting outcomes were observed from the heavy metal stress test, emphasizing the capacity of seven strains to withstand moderate to high levels of copper, zinc, nickel, cadmium, aluminium, and lead. Additionally, some selected bacterial strains exhibited positive results in drought tolerance and EPS production, indicating their potential involvement in maintaining the hydration of salamander skin. Molecular identification and phylogenetic analysis allowed us to identify most isolates as Bacillus sp. and Streptomyces sp. Understanding the cutaneous microbiota of Speleomantes increases our knowledge about its implications for amphibian ecology and health, leading to improved conservation strategies. Our preliminary results lay the groundwork for describing the cutaneous microbiota of the genus Speleomantes, exploring its potential role in contributing to the production of cutaneous secretions and mitigating environmental stresses. This study received funding from the European Union – Next-GenerationEU – National Recovery and Resilience Plan (NRRP) –MISSION 4 COMPONENT 2, INVESTIMENT N. 1.1., CALL PRIN 2022 PNRR D. .D. 1409 del 14-09-2022 – (METALCAVE).