Trophic Structure of Amoeba Communities Near Roots of Medicago sativa After Contamination with Fuel Oil No. 6

• Published in: Microbial ecology 2014-02, Vol.67 (2), p.430-442
• Main Authors: Cortés-Pérez, Sandra, Rodríguez-Zaragoza, Salvador, Mendoza-López, Ma. Remedios
• Format: Article
• Language: English
• Subjects: Alfalfa; Amoeba; Amoeba - growth & development; Amoeba - isolation & purification; Bacteria; bacterivores; Biodegradation, Environmental; Biological and medical sciences; Biomedical and Life Sciences; Community structure; Ecology; Environmental Pollution - analysis; exudation; fuel oils; Fuel Oils - analysis; Fundamental and applied biological sciences. Psychology; fungal communities; Genera; Geoecology/Natural Processes; Hydrocarbons; Hydrocarbons - chemistry; Life Sciences; Medicago sativa; Medicago sativa - microbiology; Microbial activity; Microbial Ecology; Microbiology; Microcosms; Nature Conservation; Oil pollution; Omnivores; Organic matter; Phytoremediation; Plant Roots - microbiology; Polluted soils; pollution; Predators; Protozoa; Roots; Soil contamination; Soil ecology; Soil fauna; SOIL MICROBIOLOGY; Soil Pollutants - analysis; Soil pollution; species diversity; Species richness; Water Quality/Water Pollution
• ISSN: 0095-3628; 1432-184X
• DOI: 10.1007/s00248-013-0305-1

Root exudation increases microbial activity, selecting bacterial and fungal communities that metabolize organic matter such as hydrocarbons. However, a strong contamination pulse of hydrocarbons around plant roots may reorganize the soil's microbial trophic structure toward amoebae feeding on bacteria. We conducted a microcosm experiment to elucidate the effect of Medicago sativa on the trophic structure of naked amoebae after a strong pulse of pollution (50,000 ppm of fuel oil no. 6, which is a mixture of long chains ranging from C10 to C28). Plants were seeded 24 h after contamination and species of amoebae in the microcosms were identified at 1, 30, and 60 days after pollution. Several species from three trophic groups of naked amoeba were still alive 24 h after the hydrocarbon pulse. Non-planted microcosms harbored three trophic groups after 60 days, while planted ones nourished four groups. The bacterivore group was the most diverse in all microcosms, followed by protist-eaters and omnivores. The quantity of amoebae was significantly higher (3.4×10³ organisms/g soil) in the planted pots than in the non-planted ones (1.3×10³ organisms/g soil after 30 days of pollution (P ≤ 0.01). The shortest hydrocarbon chains (C10–C14) disappeared or diminished in all microcosms, and the longest ones increased in the planted ones. M. sativa thus exerted a positive effect on species richness, quantity, and the composition of amoebae trophic groups in contaminated soil. This indirect effect on bacterial predators is another key factor underlying hydrocarbon assimilation by living organisms during phytoremediation.