Effect of melanin produced by a recombinant Escherichia coli on antibacterial activity of antibiotics.
A recombinant plasmid, pYL-1, containing a tyrosinase gene whose expression is under the control of a phage T5 promoter and 2 lac operators, was constructed. Escherichia coli JM109 harboring pYL-1 was used for production of bacterial melanin. A simple procedure for the isolation and purification of melanin was developed. The ultraviolet (UV)-visible light absorption spectra of melanin prepared by chemical synthesis and derived from different organisms, including bacteria, a plant and an animal source, were determined. Melanins produced by both bacteria and chemical synthesis showed a steady increase of absorption at wavelengths of UV light ranging from approximately 200-400 nm, while melanin derived either from plant or animal sources showed an additional discrete absorption peak at wavelength 280 nm upon a similar steady increase of absorption. This additional absorption peak could be due to the presence of protein-bound melanins in animal and plant sources while a free form of melanin was obtained from bacteria and chemical synthesis. Analysis of the effect of bacterial melanin on the activity of antibiotics against E. coli revealed that the activities of polymyxin B, kanamycin, tetracycline, and ampicillin were markedly reduced in the presence of melanin, whereas the activity of norfloxacin was not affected. The reduction of the antibacterial activity may result directly from the interaction of antibiotics with melanin. However, the mechanism of this interaction remains to be demonstrated.
Lin
Wen-Po
WP
Institute of Microbiology and Immunology, National Defense Medical Center, Taipei, Taiwan.
Lai
Hsing-Lung
HL
Liu
Yi-Lin
YL
Chiung
Yin-Mei
YM
Shiau
Chia-Yang
CY
Han
Jun-Ming
JM
Yang
Chuen-Mi
CM
Liu
Yu-Tien
YT
D000667:Ampicillin / Q000494:pharmacology; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D024881:Drug Resistance, Bacterial; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D007612:Kanamycin / Q000494:pharmacology; D008543:Melanins / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification / Q000494:pharmacology*; D008826:Microbial Sensitivity Tests; D015394:Molecular Structure; D009643:Norfloxacin / Q000494:pharmacology; D010957:Plasmids / Q000235:genetics; D011112:Polymyxin B / Q000494:pharmacology; D011994:Recombinant Proteins / Q000235:genetics / Q000494:pharmacology; D013057:Spectrum Analysis; D013752:Tetracycline / Q000494:pharmacology
D000900:Anti-Bacterial Agents; D008543:Melanins; D011994:Recombinant Proteins; D007612:Kanamycin; D000667:Ampicillin; D013752:Tetracycline; D011112:Polymyxin B; D009643:Norfloxacin