Effects of the humic substances of de-inking paper sludge on the antagonism between two compost bacteria and Pythium ultimum

Authors: Charest, Marie-HélèneBeauchamp, Chantal JeanneAntoun, Hani
Abstract: We investigated the in vitro influence of humic substances (HS) extracted from de-inking paper sludge compost on the inhibition of Pythium ultimum by two compost bacteria, Rhizobium radiobacter (Agrobacterium radiobacter) and Pseudomonas aeruginosa. When low concentrations (5 or 50 mgzl−1) of HS were added to the culture medium, fungal inhibition by R. radiobacter significantly increased (P < 0.01) by 2–3%. In contrast, these low levels of HS had no effect on P. ultimum inhibition by P. aeruginosa. The Fe, chelated by HS, was in part responsible for the decrease of P. ultimum inhibition by the bacteria when increasing amounts of HS were added in the culture medium. The addition of 500 mgl−1 of humic acids isolated from de-inking paper sludge compost or from fossil origin completely eliminated the inhibition of P. ultimum by R. radiobacter. This Fe effect also stimulated growth of R. radiobacter and reduced its siderophore production in a minimal medium supplemented with HS as sole source of Fe. The results showed that HS influence microbial antagonism when added to a culture medium. However, this effect varies with different factors such as the type of bacteria, concentration of HS, molecular weight and Fe content.
Document Type: Article de recherche
Issue Date: 5 January 2006
Open Access Date: 24 May 2017
Document version: AM
Permalink: http://hdl.handle.net/20.500.11794/14144
This document was published in: FEMS Microbiology Ecology, Vol. 52 (2), 219–227 (2005)
Alternative version: 10.1016/j.femsec.2004.11.017
Collection:Articles publiés dans des revues avec comité de lecture

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