Monitoring the impact of bioaugmentation with a PAH-degrading strain on different soil microbiomes using pyrosequencing

FESTA, SABRINA; MACCHI, MARIANELA; CORTES, FERNANDO; MORELLI, IRMA S.; COPPOTELLI, BIBIANA M.

Praga

Conferencia; Ecology of Soil Microorganisms 2015; 2015

Institute of Microbiology of the ASCR

Bioremediation is an environmental friendly approach for the cleanup of contaminated soils with complex mixtures of organic pollutants as polycyclic aromatic hydrocarbons (PAH). In aged contaminated soils, the perturbation caused by the contamination on native microorganism could limit the biodegradation of recalcitrant compounds, there bioaugmentation would be a treatment option.The present work studied the effects of inoculation with the strain Sphingobium sp. (AM) on a soil chronically contaminated with a petrochemical sludge (IPK+AM), containing 10 priority PAH and aliphatic hydrocarbons in high concentration, 576 mg/kg and 207 mg/kg respectively. Inoculant behavior was compared on pristine soil artificially contaminated with 2000 mg of phenanthrene/kg soil (Phe+AM) and pristine soil (PS+AM). AM was isolated from a chronically contaminated soil, is capable of degrading phenanthrene, anthracene, fluorene and pyrene; the partial sequencing of its genome showed PAH and aliphatic degradation complete pathways.Microcosms were inoculated with 1.4x108 cfu/g dry soil and incubated at 20±2°C and 21% humidity for 63 days. Non-inoculated microcosms of each soil were used as control. During incubation the PAH concentration (GC-FID), the number of PAH-degrading bacteria, dehydrogenase activity, and the genetic diversity (454-Pyrosequencing) of bacterial soil community were analyzed.Inoculation increased PAH degrading bacteria counts and phenanthrene degradation in Phe+AM, although in IPK+AM no effect on the degradation of any PAH was observed. In Phe+AM the dehydrogenase activity increased after 7 days of incubation, while IPK+AM and PS+AM didn?t show this stimulatory effect. The pyrosequencing data analysis, revealed that after 14 days of incubation, populations belonging to the genus Sphingobium became dominant in Phe+AM and IPK+AM (relative abundance 27.1% and 11.5% respectively). Hill numbers (D0, D1 and D2) indicated that inoculant produced an initial reduction on microbial diversity only in contaminated microcosms (Phe+AM and IPK-AM). However, at the end of the incubation, Phe+AM and IPK-AM achieve greater richness and diversity than their respective controls. The highly specialized strain Sphingobium sp. AM, used as inoculant in soil with complex mixtures of PAH, could establish and produce changes in the diversity of the bacterial communities, but these changes didn?t cause any improvement in global degradation efficiency on chronically contaminated soil.