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KMID : 0545120030130040564
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Journal of Microbiology and Biotechnology
2003 Volume.13 No. 4 p.564 ~ p.570
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Salmonella typhimurium LPS Confers Its Resistance to Antibacterial Agents of Baicalin of Scutellaria baicalensis George and Novobiocin: Complementation of the rfaE Gene Required for ADP-L-glycero-D-manno-heptose Biosynthesis of Lipopolysacchari
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CHUNG, TAE-WOOK
JIN, UN-HO/KIM, CHEORL-HO
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Abstract
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The antibacterial mechanism of enterohacter Salmonella typhimurium was studied. The rju (Waa) gene cluster of S. typhimun´um encodes the core oligosaccharide biosynthesis of lipopolysaccharide (LPS). Among the rfa gene cluster. we recently cloned the rfaE gene, which is involved in ADP-1.-glycero-D-manno-heptose biosynthesis. The rfuE mutant synthesizes heptose-deficient LPS, which consists of only lipid A and 3-deoxy-D-manno-octulosonic acid (KDO), thus making an incomplete LPS and a rough phenotype mutant. S. typhimurium deep-rough mutants with the heptose region of the inner core show a reduced growth rate, sensitivity to high temperature, and hypersensitivity to hydrophobic antibiotics such as baicalin isolated from the medicinal herb of Scutellaria baicalensis Georgi. Thus, in this study, the cloned rfaE gene was added to the S. typhimurium rfaE mutant strain SL1102 (rfauE.543). which makes heptose-deficient LPS and has a deep-rough phenotype. The complementation created a smooth phenotype in the SLI 102 strain. The sensitivity of SL1102 to bacteriophages was also recovered to that of wild-type strain, indicating that LPS is used as the receptor for bacteriophage infection. The permeability bamer of SLI 102 to hydrophobic antibiotics such as novobiocin and haicalin was restored to that of the wild-type, suggesting that antibiotic resistance of the wild-type strain is highly correlated with their LPS. Through an agar diffusion assay, the powth-inhibition activity of haicalin was fully observed in the mutant SL1102 strain. However, only a half of the inhibitory activity was detected in the rfaE-complemented SLI 102 strain. Furthermore, the LPS produced by the rfaE-complemented SL1102 strain was indistinguishable from LPS biosynthesis of smooth strains.
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