PHAGE-BACTERIA INTERACTIONS UNDER METAL STRESS: A STUDY OF THE NOVEL STENOTROPHOMONAS MALTOPHILIA PHAGE VB_STM18.

Stenotrophomonas maltophilia is a highly adaptable gram-negative bacteria, demonstrating resilience in metal-contaminated environment, which makes it a key subject for understanding microbial survival under heavy metal stress. This study investigates the effects of cadmium ions (Cd²⁺) on the growth dynamics, cadmium uptake, and bacteriophage vB_Stm18-host interactions, with implications for environmental microbiology and applied biotechnology. Growth analysis revealed that S. maltophilia tolerates Cd²⁺ at 0.01 g/L, although exposure prolonged the lag phase by 3 hours. Despite the initial growth inhibition, the bacterium adapted and achieved control-like growth levels by 18 hours. Bioaccumulation assays showed progressive cadmium uptake, reaching 1876 µg/g at 24 hours, highlighting its potential for bioremediation. The influence of Cd²⁺ on phage vB_Stm18's life cycle was assessed through adsorption efficiency and burst size measurements. Short-term exposure to Cd²⁺ caused minimal reductions in adsorption efficiency (97% vs. 98% in control) but significantly decreased the burst size to 17 particles per infected cell. Prolonged exposure exacerbated these effects, with adsorption efficiency decreasing to 58% and burst size dropping to 6 particles per infected cell, after 18 hours of pre-incubation. These findings suggest that cadmium alters bacterial surface structures, intracellular processes and disrupts phage replication and release. Therefore, this study sheds light on the molecular interplay between environmental pollutants and microbial systems providing valuable insights into microbial ecology in metal-contaminated habitats as well as informing strategies for optimizing phage therapy and bioremediation under heavy metal stress.