Pseudomonas aeruginosa strain CD3 implements cadmium resistance through multimodal systems and its regulatory networking

Cadmium, a toxic heavy metal, poses a significant global concern. Out of 26 cadmium-resistant bacteria isolated from Malda, West Bengal, India, 10 exhibited significant resistance to cadmium. The study hypothesized that the net availability of metal salt molecules in a dissolved state would determine the tolerance limit of a given bacterium towards a particular heavy metal. Experiments were conducted using a modified medium that supported maximum bioavailability of cadmium, and strain CD3 was selected for studying the growth and induction of cadmium resistance. The resistance levels of CD3 cells increased with increasing initial cell numbers. Biofilm formation increased at lower concentrations of CdCl ₂ .H ₂ O but decreased as concentrations exceeded 0.75 mM. Atomic-absorption-spectrophotometry data confirmed that the efflux pump played a critical role in cadmium resistance at higher concentrations. Using whole-genome-based phylogenetic tools, strain CD3 was found to be the closest relative to Pseudomonas aeruginosa DSM50071 ^T among the type strains of Pseudomonas spp., highlighting its unique evolutionary path. The STRING database was used to uncover an intricate web of protein-protein interactions. Hence, bioinformatic analyses revealed a complex network of regulations, with BfmR playing a crucial role in the functions of CzcR and CzcS, essential for biofilm formation and receptor signalling pathways.