Indole induces IifC expression by IifR in Acinetobacter baumannii

• Main Authors: Fang-Wei Tsai, 蔡芳偉
• Other Authors: Guang-Huey Lin
• Format: Others
• Language: zh-TW
• Published: 2014
• Online Access: http://ndltd.ncl.edu.tw/handle/q8zm9t

碩士 === 慈濟大學 === 微生物學免疫學暨生物化學碩士班 === 103 === Acinetobacter baumannii is an aerobic gram-negative bacterium, rod shape and no flagellum that is resistant to most antibiotics. As a result of its resistance to antibiotics, it became a multidrug-resistant Acinetobacter baumannii. It can survive at nature environment such as water, soil or fruits and vegetables. It is one of the most important nosocomial pathogens. The prolonged inpatients are vulnerable to its infection and develop to bacteremia, pneumonia, meningitis, urinary tract infection and wound infection. We found that two gene clusters can oxidaze indole into indoxyl in Escherichia coli which can metabolize tryptophan into indole, one of them is iif operon in Acinetobacter baumannii ATCC19606. There are five genes which are ABA1787 to ABA1783 in the iif operon. ABA1785 is an important gene in this operon and is named indole induced flavoprotein monooxygenase C (iifC). ABA1782 which is named iif operon regulator (iifR) is putative AraC family regulatory protein. IifR is located downstream of a gene cluster containing iifC, which may be a metabolism-related gene. However, how IifR regulate iif operon to transcription is still unknown. In this study, the mutant strains which were constructed by Dr. Hung-Yu Shu were cultured with different carbon source in M9 medium and compared with wild type in IifC and IifR protein levels. The result showed that indole is the ligand of IifR, and indole can induce IifC expression by IifR. We found that IifC and IifR were not associated with biofilm formation and response of oxidative stress. However, IifC and IifR were associated with oxidation of indole and resistance of tetracycline. We found that IifR can bind with iif promoter region by ChIP assay. Taken together, indole can induce IifC expression, while iifR mutant strains could not induce IifC expression suggesting that IifR can induce IifC expression with indole. We found that supernatant of indole-producing bacteria also can induce IifC expression. Tetracycline MIC of iifC and iifR mutant strains are lower than that of wild type suggesting that IifC plays a role in interference of indole signal and resistance of tetracycline.