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Low molecular weight organic anions (carboxylates) increase microbial activity and alter microbial community composition in uncontaminated and diesel contaminated soil

Martin, B.C., George, S.J., Price, C.A., Shahsavari, E., Ball, A.S., Tibbett, M. and Ryan, M.H. (2016) Low molecular weight organic anions (carboxylates) increase microbial activity and alter microbial community composition in uncontaminated and diesel contaminated soil. Soil .

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Free to read: https://doi.org/10.5194/soil-2016-30
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Abstract

Petroleum hydrocarbons (PHCs) are among the most prevalent sources of environmental contamination. It has been hypothesized that plant root exudation of low molecular weight organic acid anions (carboxylates) may aid degradation of PHCs by stimulating heterotrophic microbial activity. We, therefore, applied two commonly-exuded carboxylates (citrate and malonate) to uncontaminated and diesel contaminated microcosms (10,000 mg kg–1; aged 40 days) to determine their impact on the microbial community and PHC degradation. Every 48 hours for 18 days, soil received 5 μmol g–1 of i) citrate, ii) malonate, iii) citrate + malonate or iv) water. Microbial activity was measured daily as the flux of CO2. After 18 days, changes in the microbial community were assessed by community level physiological profiles and 16S rRNA bacterial community profiles determined by denaturing gradient gel electrophoresis. Saturated PHCs remaining in the soil were assessed by GCMS. Cumulative soil respiration increased four- to six-fold with the addition of carboxylates, while diesel contamination resulted in a small, but similar, increase across all carboxylate treatments. The addition of carboxylates resulted in distinct changes to the microbial community, but only a small decrease in the n-C17: pristane biomarker. We conclude that carboxylate addition can increase microbial activity and modify the microbial community in both uncontaminated and diesel-contaminated soils. The impact of these changes on PHC biodegradation and rhizosphere processes, more generally, merits further research.

Item Type: Journal Article
Publisher: European Geosciences Union
Copyright: © 2016 The Authors.
URI: http://researchrepository.murdoch.edu.au/id/eprint/66427
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