Relationship between structures of substituted indolic compounds and their degradation by marine anaerobic microorganisms

Ji Dong Gu*, Yanzhen Fan, Hanchang Shi

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

45 Scopus citations


Degradation of selected indolic compounds including indole, 1-methylindole, 2-methylindole, and 3-methylindole was assessed under methanogenic and sulfate-reducing conditions using the serum-bottle anaerobic technique and marine sediment from Victoria Harbour, Hong Kong as an inoculum. Our results showed that indole degradation was achieved in 28 days by a methanogenic consortium and 35 days by a sulfate-reducing consortium. During degradation under both conditions, two intermediates were isolated, purified and identified as oxindole and isatin (indole-2,3-dione) suggesting that both methanogenic and sulfate-reducing bacteria use an identical degradation pathway. Degradation processes followed two steps of oxidation accomplished by hydroxylation and then dehydrogenation at 2- and then 3-position sequentially prior to the cleavage of the pyrrole ring between 2- and 3-positions. However, none of 1-methylindole or 2-methylindole was degraded under any conditions. 3-Methylindole (3-methyl-1H-indole, skatole) was transformed under methanogenic conditions and mineralized only under sulfate-reducing conditions. It is clear that methyl substitution on 1- or 2-position inhibits the initial attack by hydroxylation enzymes making them more persistent in the environment and posing longer toxic impact.

Original languageEnglish
Pages (from-to)379-384
Number of pages6
JournalMarine Pollution Bulletin
Issue number1-12
StatePublished - Sep 2002
Externally publishedYes


  • Anaerobic degradation
  • Indole
  • Metabolic pathway
  • Methanogenic condition
  • Substitution
  • Sulfate-reducing condition


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