Construction and phenotypic study of Pseudomonas aeruginosa inducibly expressing a ferric uptake regulator / 生物工程学报

Members of the ferric uptake regulator (Fur) protein family are bacterial transcriptional repressors that control iron uptake and storage in response to iron availability, thereby playing a crucial role in the maintenance of iron homeostasis. The fur null mutants of Pseudomonas aeruginosa could not be obtained because fur is an essential gene. In this study, We constructed a Fur inducibly expression strain Δfur/attB::PBAD-fur in order to study the effect of fur on the growth, biofilm formation, motilities and oxidative stress response of P. aeruginosa. The results showed that a low level of fur expression retarded the growth of P. aeruginosa at an iron-depleted condition, or under high concentration of iron, or in the presence of H2O2. Fur affected the biofilm formation and the motilities (swimming, twitching, and swarming) of strain PAO1. The production of pyoverdine is regulated by Fur. Interestingly, proteins from Magnetospirillum gryphiswaldense MSR-1, which shares homology with Fur, can partially recover the pyoverdine production of strain Δfur/attB::PBAD-fur. This study provides new clues for the prevention and treatment of P. aeruginosa infections.

Vibrio vulnificus Hemolysin Is Easily Inactivated in Spite of Being Produced at High Levels in Cirrhotic Ascites by a fur Mutation

Vibrio vulnificus produces Hemolysin/cytolysin (VvhA), which is one of the most potent exotoxins capable of killing mice at submicrogram levels. However, V. vulnificus growth and vvhA expression are severely repressed and extracellular VvhA produced at low levels is easily inactivated in human body fluids. This study was conducted to obtain additional unequivocal evidence of the enigmatic characteristic of VvhA. V. vulnificus growth was stimulated, vvhA expression was de-repressed, and extracellular VvhA production was increased in cirrhotic ascites, a human ex vivo experimental system, by a mutation of fur encoding ferric uptake regulator, which acts as a transcriptional repressor. However, regardless of the presence or absence of the fur mutation, extracellular VvhA activity was not detected in cirrhotic ascites. These results indicate that VvhA is easily inactivated even when vvhA expression and extracellular VvhA production are maintained at high levels in cirrhotic ascites.