Fluorescent pseudomonads occuring in Macrotermes subhyalinus mound structures decrease Cd toxicity and improve its accumulation in sorghum plants

Duponnois Robin, Kisa Marija, Assigbetse Komi, Prin Yves, Thioulouse Jean, Issartel M., Moulin Patricia, Lepage Michel. 2006. Fluorescent pseudomonads occuring in Macrotermes subhyalinus mound structures decrease Cd toxicity and improve its accumulation in sorghum plants. Science of the Total Environment, 370 (2-3) : 391-400.

https://doi.org/10.1016/j.scitotenv.2006.07.008

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Résumé : Cd-tolerant bacterial strains of fluorescent pseudomonads, mostly belonging to Pseudomonas monteillii, were isolated from termite mound soil (Macrotermes subhyalinus, a litter-forager and fungus-growing termite), in a Sudanese shrubby savanna, Burkina Faso. Such large mounds appeared as sites of great bacterial diversity and could be considered as hot spots of metal-tolerant fluorescent pseudomonads. Microbial isolates were inoculated to Sorghum plants (S. bicolor) in glasshouse experiments with soil amended with CdCI2 (560 mg Cd kg-1 soil). Microbial functional diversity was assessed at the end of the experiment by measurement of in situ patterns of catabolic potentials. All the bacteria isolates significantly improved the shoot and total biomass of sorghum plants compared to the control. Results concerning root biomass were not significant with some strains. Arbuscular mycorrhiza (AM) was greatly reduced by CdCI2 amendment, and fluorescent pseudomonad inoculation significantly increased AM colonisation in the contaminated soil. The bacterial inoculation significantly improved Cd uptake by sorghum plants. Measurement of catabolic potentials on 16 substrates showed that the microbial communities were different according to the soil amendment. Soils samples inoculated with pseudomonad strains presented a higher use of ketoglutaric and hydroxybutiric acids, as opposed to fumaric acid in soil samples not inoculated. It is suggested that fluorescent pseudomonads could act indirectly in such metabolic processes by involving a lower rate of degradation of citric acid, in line with the effect of small organic acid on phyto-extraction of heavy metals from soil. This is a first contribution to bioremediation of metal-contaminated sites with soil-to-plant transfer, using termite built structures. Further data are required on the efficiency of the bacterial strains isolated and on the processes involved. © 2006 Elsevier B.V. All rights reserved.

Mots-clés Agrovoc : Sorghum bicolor, cadmium, sol pollué, métal lourd, micro-organisme du sol, Mycorhizé, Pseudomonas fluorescens, Termitidae, bioremédiation, relation plante sol

Mots-clés géographiques Agrovoc : Burkina Faso

Mots-clés complémentaires : Endomycorhize à vésicules et arbuscules, Pseudomonas monteillii, Inoculum

Classification Agris : P34 - Biologie du sol
P02 - Pollution
F62 - Physiologie végétale - Croissance et développement

Champ stratégique Cirad : Axe 1 (2005-2013) - Intensification écologique

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