Identification and characterization of an indigo-producing oxygenase involved in indole 3-acetic acid utilization by Acinetobacter baumannii.
Acinetobacter baumannii harbours a gene cluster similar to the iac locus of Pseudomonas putida 1290, which can catabolize the plant hormone indole 3-acetic acid (IAA) as an energy source. However, there has been no evidence showing that IAA can be utilized by A. baumannii. This study showed that A. baumannii can grow in M9 minimal medium containing IAA as the sole carbon source. A mutagenesis study indicated that iacA, encoded in the iac locus of A. baumannii, is involved in the catabolism of IAA. As shown by western blotting analysis, the IacA protein was detected in A. baumannii grown in M9 minimal medium with IAA but not with pyruvate, suggesting that the expression of iacA is regulated by the presence of IAA. In vitro studies have shown that IacA can oxidize indole, an IAA-like molecule, converting it to indoxyl, which spontaneously dimerises to form indigo. In this study, we show that the crude extracts from either wild-type A. baumannii or Escherichia coli overexpressing IacA can oxidize IAA. These results imply that the iac gene cluster of A. baumannii is involved in IAA degradation and that the iacA gene is upregulated when cells encounter IAA in their native environments.
Microbial Genetics Laboratory, Department of Microbiology, Tzu-Chi University, Hualien, Taiwan.
Guang-Huey
GH
Lin
Hao-Ping
HP
Chen
Jui-Hsin
JH
Huang
Tze-Tze
TT
Liu
Tze-Kang
TK
Lin
Shih-Jon
SJ
Wang
Cheng-Hsing
CH
Tseng
Hung-Yu
HY
Shu
D040981:Acinetobacter baumannii / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism; D015153:Blotting, Western; D003470:Culture Media / Q000737:chemistry; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D007203:Indigo Carmine; D007210:Indoleacetic Acids / Q000378:metabolism*; D007211:Indoles / Q000378:metabolism*; D010084:Oxidation-Reduction; D010105:Oxygenases / Q000235:genetics* / Q000378:metabolism*
D003470:Culture Media; D007210:Indoleacetic Acids; D007211:Indoles; C034082:indoxyl; C030737:indoleacetic acid; D007203:Indigo Carmine; D010105:Oxygenases