From the biodiversity of hydrothermal vents towards the discovery of new biologically active natural molecules

Hydrothermal vents are seafloor fissures that emit geothermally heated, mineral-rich water resulting from interactions between Earth's crust layers and various minerals. Often, they are found near volcanic regions or tectonic plate boundaries. Each hydrothermal vent has unique characteristics shaped by its interaction with different types of rocks, and its fluids vary in temperature, ranging from 20°C to 135°C, or pH, ranging from acidic to basic, which creates harsh environments. Since their discovery, hydrothermal vents and their unique chemical and physical properties have captured the scientific community's attention. Over the past few decades, research has primarily focused on studying the microbial communities in these environments, but their complexity remains poorly understood.This project aims to study the microbial community of the Sicilian hydrothermal vents, focusing on two hydrothermal systems: the first on the west coast of Sicily, near Trapani, and the second in the Aeolian Archipelago, near Panarea. The hydrothermal water on the west coast of Sicily reaches a temperature of 31°C. The bacterial communities associated with two marine invertebrates living near this hydrothermal vent are investigated: the sponge belongs to the Petrosia ficiformis species, and the nudibranch belongs to the Peltodoris atromaculata species. On the other side, the hydrothermal vent called Black Point is investigated for its peculiar chemical and physical parameters in two sampling expeditions: the first conducted in May and the second in August 2022. Indeed, this hydrothermal vent shows high temperatures (135°C), low pH (3.5), and high concentrations of minerals in its hydrothermal fluids.Moreover, bacteria living in these harsh environments produce unknown compounds, such as novel secondary metabolites or enzymes. For this reason, novel microorganisms are isolated from Black Point in different media and tested for producing CaCO3, enzymes, and secondary metabolites with antimicrobial properties. In addition, to fight the rise of antimicrobial resistance, different recombinant Actinomycetes strains are created and screened.The characterization of the hydrothermal vent near Trapani shows that the bacterial communities associated with the sponge Petrosia ficiformis and the mantle of Peltodoris atromaculata show remarkable similarities. However, they also display distinct differences, which could be attributed to the unique environmental conditions of each host. Indeed, specific bacterial families, such as Caldilineaceae, are identified in P. atromaculata gut and mantle.Furthermore, analyzing samples obtained in May and August from Black Point reveals notable differences in microbial abundance and diversity across hydrothermal water, seawater, and marine sediments. The prevalence of specific microbial taxa shifts between the sampling periods, emphasizing the impact of temporal changes and environmental factors, including temperature, pH, and chemical composition. Finally, among the forty-five isolates, thirty-four produce enzymes, and four produce CaCO3. Moreover, one isolate from Panarea and one recombinant strain of Actinomycetes produce secondary metabolites with antimicrobial properties. This project provides new insights into the microbial community of hydrothermal vents and the bacterial isolates from this extreme environment. Additionally, it offers a novel approach to fighting antimicrobial resistance.