GENOMIC AND PHYSIOLOGICAL INSIGHTS INTO BACTERIAL HEAVY METAL RESISTANCE MECHANISMS FOR ENVIRONMENTAL DECONTAMINATION

The contamination of soils and waters with heavy metals (HM) such as chromium, copper, zinc and cadmium represents one of the most severe environmental challenges, posing risks to ecosystem balance and human health. Microorganisms and plants have evolved a range of mechanisms to tolerate, transform and immobilize these pollutants, offering opportunities for sustainable bioremediation strategies. The aim of this PhD thesis was to investigate how bacteria can contribute to the removal and detoxification of heavy metals. The work is structured to explore complementary aspects: (1) Analyses of extracellular polymeric substances (EPS) and biofilm formation of Serratia plymuthica strain As3-5a(5) highlight the role of tightly bound EPS in Cu removal from industrial wastewaters; (2) Genome sequencing and transcriptomic analysis of Rhodococcus erythropolis strain SC26 provide insights into its Cr(VI) reduction pathways; (3) Characterization of Cd resistance and plant growth-promoting (PGP) bacteria contributes to knowledge of plant-microbial interactions to alleviate Cd stress in plants; (4) Characterization of microbial communities in heavy metal- hydrocarbon contaminated area demonstrates how ecological indicators can support rhizoremediation assessment. Collectively, these findings contribute to a deeper understanding of microbial and plant-microbe interactions in metal-contaminated environments, and support the development of innovative, eco- compatible strategies to mitigate heavy metal pollution and promote ecosystem restoration.