The iron-sulphur cluster biosynthesis regulator IscR contributes to iron homeostasis and resistance to oxidants in Pseudomonas aeruginosa.
IscR is a global transcription regulator responsible for governing various physiological processes during growth and stress responses. The IscR-mediated regulation of the Pseudomonas aeruginosa isc operon, which is involved in iron-sulphur cluster ([Fe-S]) biogenesis, was analysed. The expression of iscR was highly induced through the exposure of the bacteria to various oxidants, such as peroxides, redox-cycling drugs, intracellular iron-chelating agents, and high salts. Two putative type 1 IscR-binding sites were found around RNA polymerase recognition sites, in which IscR-promoter binding could preclude RNA polymerase from binding to the promoter and resulting in repression of the isc operon expression. An analysis of the phenotypes of mutants and cells with altered gene expression revealed the diverse physiological roles of this regulator. High-level IscR strongly inhibited anaerobic, but not aerobic, growth. iscR contributes significantly to the bacteria overall resistance to oxidative stress, as demonstrated through mutants with increased sensitivity to oxidants, such as peroxides and redox-cycling drugs. Moreover, the regulator also plays important roles in modulating intracellular iron homeostasis, potentially through sensing the levels of [Fe-S]. The increased expression of the isc operon in the mutant not only diverts iron away from the available pool but also reduces the total intracellular iron content, affecting many iron metabolism pathways leading to alterations in siderophores and haem levels. The diverse expression patterns and phenotypic changes of the mutant support the role of P. aeruginosa IscR as a global transcriptional regulator that senses [Fe-S] and directly represses or activates the transcription of genes affecting many physiological pathways.
Department of Biotechnology, Faculty of Science, Mahidol University, Bangkok, Thailand ; Laboratory of Biotechnology, Chulabhorn Research Institute, Bangkok, Thailand.
Adisak
A
Romsang
Laboratory of Biotechnology, Chulabhorn Research Institute, Bangkok, Thailand.
Jintana
J
Duang-Nkern
Molecular Medicine Graduate Program, Faculty of Science, Mahidol University, Bangkok, Thailand.
Panithi
P
Leesukon
Department of Biotechnology, Faculty of Science, Mahidol University, Bangkok, Thailand.
Kritsakorn
K
Saninjuk
Laboratory of Biotechnology, Chulabhorn Research Institute, Bangkok, Thailand ; Program in Applied Biological Science: Environmental Health, Chulabhorn Graduate Institute, Bangkok, Thailand ; Center of Excellence on Environmental Health and Toxicology, Ministry of Education, Bangkok, Thailand.
Paiboon
P
Vattanaviboon
Department of Biotechnology, Faculty of Science, Mahidol University, Bangkok, Thailand ; Center for Emerging Bacterial Infections, Faculty of Science, Mahidol University, Bangkok, Thailand ; Laboratory of Biotechnology, Chulabhorn Research Institute, Bangkok, Thailand ; Center of Excellence on Environmental Health and Toxicology, Ministry of Education, Bangkok, Thailand.
Skorn
S
Mongkolsuk
D000595:Amino Acid Sequence; D001483:Base Sequence; D040461:Gene Components; D020869:Gene Expression Profiling; D015964:Gene Expression Regulation, Bacterial / Q000187:drug effects / Q000235:genetics*; D007501:Iron / Q000378:metabolism; D007502:Iron Chelating Agents / Q000494:pharmacology; D007506:Iron-Sulfur Proteins / Q000096:biosynthesis / Q000378:metabolism*; D018384:Oxidative Stress / Q000502:physiology; D010545:Peroxides / Q000494:pharmacology; D011401:Promoter Regions, Genetic / Q000235:genetics; D011550:Pseudomonas aeruginosa / Q000235:genetics* / Q000502:physiology; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D014157:Transcription Factors / Q000235:genetics*
D007502:Iron Chelating Agents; D007506:Iron-Sulfur Proteins; D010545:Peroxides; D014157:Transcription Factors; D007501:Iron