Revealing the Biosynthetic Potential of Marine Microorganisms: Production of Novel Biosurfactants, Siderophores and Antimicrobials for Biotechnological Applications

Blue Biotechnology focuses on the use of marine microorganisms and their secondary metabolites to address global challenges such as antibiotic resistance, climate change and environmental sustainability. Natural products are attracting increasing interest for their unique properties and therapeutic potential, with applications ranging from medicine to environmental protection. In particular, marine extremophilic bacteria represent an under-explored source for the discovery of novel bioactive metabolites due to their ability to thrive in extreme environmental conditions such as high salinity, elevated pressure, extreme temperatures, high UV irradiation, and low-nutrient environments. Their metabolic diversity is driven by biosynthetic gene clusters (BGCs) that regulate compound production. Among relevant bio-based products, biosurfactants represent a viable alternative to synthetic surfactants, as they are secreted molecules that reduce interfacial liquid tension, endowed with multiple bioactivities and a high level of biodegradability. Siderophores, iron-chelating agents, support microbial survival and hold significant potential in bioremediation and developing strategies to combat antimicrobial resistance (AMR). Furthermore, antimicrobial compounds derived from marine extremophiles are increasingly recognized for their ability to treat infections caused by multidrug-resistant pathogens. This PhD research contributes to exploring the biosynthetic potential of marine extremophilic bacteria (deep-sea, halophilic and tropical bacteria) by combining functional screening, genome analysis and chemical characterization of relevant metabolites. In particular, in three main chapters, this PhD project I) reveals the NRPS biosynthesis of novel nobilamide molecules along with known surfactins produced by a deep-sea Bacillus sp. BCP32, with antimicrobial activity against MDR bacteria, II) identifies new aquachelin siderophores and their previously unknown biosynthetic gene cluster (BGC) from a marine Halomonas and III) describes the isolation and characterization of two novel coral-associated microorganisms (CAMs) displaying potent antimicrobial, antioxidant and UV protectant properties.