Abstract: A facultative anaerobic bacterium which was a highly efficient humic substances and Fe (III)-reducing bacterium (designated CY01), was isolated from an ancient forest soil from Guangzhou, China and was identified as a strain of Comamonas koreensis. The role of the humic model compound, anthraquinone-2,6-disulfonate (AQDS), in the anaerobic reductive dechlorination of 2,4-dichlorophenoxyacetic acid (2,4-D) by C. koreensis CY01 was investigated. 1) Strain CY01 could couple glucose oxidation to 2,4-D reductive dechlorination; 2) Reductive dechlorination of 2,4-D by strain CY01 was greatly stimulated by the addition of AQDS which acts as an electron shuttle. 2,4-D reduction proceeded by oxidation of electron donors and transference of electrons to the acceptors through the redox mediator, AQDS.