Insulin Affects Biological Behaviours of Pseudomonas aeruginosa

Background: It is well known that host factors are capable of regulating microbial behaviours such as growth, metabolic pathways, virulence properties, and antimicrobial susceptibilities. In this respect, the present study aimed to investigate the relationship between insulin and various virulence properties of Pseudomonas aeruginosa ATCC 27853. Methods: Growth alterations, biofilm formation, motility, haemolytic activity, and pigment production (pyocyanin and pyoverdine) were determined in the presence/absence of three different insulin concentrations (10 µU/mL -20 µU/mL -200 µU/mL) under in vitro conditions. In addition, changes in bacterial virulence were evaluated in an in vivo animal (Caenorhabditis elegans) model. Alterations in growth, haemolytic activity, and pigment production were investigated spectrophotometrically. Biofilm formation was examined using the crystal violet well-plate assay. A soft agar plate method was used to detect swimming motility. Results: According to the results, all three insulin concentrations enhanced the bacterial growth. On the other hand, biofilm production, swimming motility, and haemolytic activity decreased in the presence of all insulin concentrations. Pyocyanin production was shown to be increased in the presence of only 10 µU/mL of insulin, but pyoverdine production did not change. In vivo animal survival rates showed that 200 µU/mL of insulin decreased bacterial virulence. Conclusions: This research demonstrates that P. aeruginosa can sense and respond to mammalian hormones (insulin), which can modulate microbial virulence through diverse mechanisms, providing new insights that may be relevant to infection dynamics.