In modified Winogradsky's (MW) medium supplemented with excessive indole (
1),
Burkholderia unamae strain CK43B isolated from polyphenol-rich
Shorea rhizosphere showed almost no cell growth, but it showed drastic cell growth given further supplementation of gallic acid, a simple plant polyphenol. This active cell growth of
B. unamae CK43B was due to the stimulating effect of gallic acid on
1-degradation of bacterial cells, which acquired a nitrogen source in
1. Under aerobic culture conditions with appropriate concentrations (0.5–2.0 m
M) of gallic acid,
B. unamae CK43B started to decompose exogenous
1 in a dose-dependent manner, and finally accumulated catechol (
5)
via anthranilic acid (
4). Pyrogallol also showed a cometabolic effect on decarboxylation-coupled oxidative deamination of
B. unamae CK43B, producing
5 from
4, as gallic acid did. These results suggest that pyrogallol-type plant polyphenols act as stimulators on
B. unamae CK43B, causing it to degrade an
N-heterocyclic aromatic compound (NHAC) including nitrogen-containing humic substances.
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