Sz-Yun Pan1, Yung-Luen Shih2, Hsin-Hui Huang1, Li-Hua Li3, Yi-Tsung Lin4, Tsuey-Ching Yang5. 1. Department of Biotechnology and Laboratory Science in Medicine, National Yang-Ming University, Taipei, Taiwan, ROC. 2. Department of Pathology and Laboratory Medicine, Shin Kong Wu Ho-Su Memorial Hospital, Taipei, Taiwan, ROC; School of Medical Laboratory Science and Biotechnology, Taipei Medical University, Taipei, Taiwan, ROC; School of Medicine, College of Medicine, Fu-Jen Catholic University, New Taipei City, Taiwan, ROC. 3. Department of Pathology and Laboratory Medicine, Taipei Veterans General Hospital, Taipei, Taiwan, ROC; Program of Medical Biotechnology, Taipei Medical University, Taipei, Taiwan, ROC. 4. Division of Infectious Diseases, Department of Medicine, Taipei Veterans General Hospital, Taipei, Taiwan, ROC; School of Medicine, National Yang-Ming University, Taipei, Taiwan, ROC. 5. Department of Biotechnology and Laboratory Science in Medicine, National Yang-Ming University, Taipei, Taiwan, ROC. Electronic address: tcyang@ym.edu.tw.
Abstract
BACKGROUND: Stenotrophomonas maltophilia, a species of highly genetic diversity, has emerged as an important nosocomial pathogen. S. maltophilia and Pseudomonas aeruginosa are often co-isolated from pneumonia patients. In our previous study, we have demonstrated that the pacIRA cluster present in some but not all clinical S. maltophilia isolates. Proteins encoded by pacIRA operon are an extracytoplasmic function (ECF) sigma factor, a transmembrane anti-sigma regulator, and a TonB-dependent receptor. This study aimed to elucidate PacIRA system function and its significance to S. maltophilia. METHODS: The pacI, pacR, and pacA genes were individually or totally deleted from the chromosome of KJΔEnt, a pacIRA-positive and siderophore-null strain. Growth promotion assay was performed to examine the implication of pacIRA system in iron utilization. Gene expression was quantified by quantitative real time PCR (qRT-PCR). Growth competition assay was executed to investigate the significance of pacIRA operon to S. maltophilia. RESULTS: PacIRA system contributed to utilize ferri-pyochelin of P. aeruginosa as iron sources for growth in an iron-depleted condition, but hardly utilized ferric citrate, hemin, ferri-stenobactin, and ferri-pyoverdine. PacIRA was founded to belong to Fur regulon and upregulated in response to iron-depleted stress. Growth competition assay demonstrated that pacIRA-positive S. maltophilia had a superiority over pacIRA-negative S. maltophilia in iron acquisition when they were co-cultured in P. aeruginosa ferri-pyochelin-supplemented medium. CONCLUSIONS: PacIRA system of S. maltophilia is a xenosiderophore uptake implement, involving in the acquisition of pyochelin of P. aeruginosa.
BACKGROUND: Stenotrophomonas maltophilia, a species of highly genetic diversity, has emerged as an important nosocomial pathogen. S. maltophilia and Pseudomonas aeruginosa are often co-isolated from pneumonia patients. In our previous study, we have demonstrated that the pacIRA cluster present in some but not all clinical S. maltophilia isolates. Proteins encoded by pacIRA operon are an extracytoplasmic function (ECF) sigma factor, a transmembrane anti-sigma regulator, and a TonB-dependent receptor. This study aimed to elucidate PacIRA system function and its significance to S. maltophilia. METHODS: The pacI, pacR, and pacA genes were individually or totally deleted from the chromosome of KJΔEnt, a pacIRA-positive and siderophore-null strain. Growth promotion assay was performed to examine the implication of pacIRA system in iron utilization. Gene expression was quantified by quantitative real time PCR (qRT-PCR). Growth competition assay was executed to investigate the significance of pacIRA operon to S. maltophilia. RESULTS: PacIRA system contributed to utilize ferri-pyochelin of P. aeruginosa as iron sources for growth in an iron-depleted condition, but hardly utilized ferric citrate, hemin, ferri-stenobactin, and ferri-pyoverdine. PacIRA was founded to belong to Fur regulon and upregulated in response to iron-depleted stress. Growth competition assay demonstrated that pacIRA-positive S. maltophilia had a superiority over pacIRA-negative S. maltophilia in iron acquisition when they were co-cultured in P. aeruginosa ferri-pyochelin-supplemented medium. CONCLUSIONS: PacIRA system of S. maltophilia is a xenosiderophore uptake implement, involving in the acquisition of pyochelin of P. aeruginosa.