Pyrosequencing reveals bioaugmentation impact on the dynamics of bacterial community on phenanthrene-contaminated soil

FESTA S; B.M. COPPOTELLI; I .S. MORELLI

Praga

Conferencia; Ecology of Soil Microorganisms 2015; 2015

Institute of Microbiology of the ASCR

Bioaugmentation, the adding of allochthonous degrading bacteria or consortium, is a complex technique because its effectivity depends on the interaction between the inocula and the indigenous population. The impact of the inoculation of a phenanthrene-degrading consortium (CON) and a Sphingobium strain (AM), isolated from the CON, on soil bacterial community dynamics was evaluated on phenanthrene-contaminated soil. The shift produced by AM on the bacterial community of unpolluted soil was also determined. The bioaugmentation studies were performed in soil microcosms contaminated with 2 g of phenanthrene/Kg dry soil. The microcosms were inoculated with 1.4x108 cfu/g dry soil, and incubated for 63 days. An unpolluted soil microcosm was inoculated with the strain AM. The respective non-inoculated microcosms were used as control. The phenanthrene concentration (HPLC) was determined at different times and 16S rRNA gene pyrosequencing analysis was performed at 14 and 63 days of treatment.After 63 days of incubation, the phenanthrene concentration in non-inoculated microcosm was 73 mg/Kg dry soil; the inoculated microcosms with CON and AM showed phenanthrene concentrations significantly lower, 24 and 6 mg/Kg dry soil respectively. Pyrosequencing generated a mean of 4743 quality-filtered reads per sample that were grouped into 2228 OTUs using 97% similarity. According rarefaction curves the number of sequences was enough to cover most of the diversity. The Hill-numbers showed a reduction in bacterial richness (0D) and diversity (1D, 2D) in all contaminated microcosms. This effect was not noticed in the inoculated unpolluted soil microcosm. After 63 days of treatment, only the inoculated microcosms recovered 0D values similar to the control, but with a reduced diversity. The contamination with phenanthrene produced a stimulatory effect on the orders Actinomycetales, Burkholderiales and Sphingomonadales. Whereas the predominance of Actinomycetales and Sphingomonadales increase after 63 days of treatments, the Burkholderiales rapidly decline. Both inoculums produced an additional increase of Burkholderiales and Sphingomonadales, with a relative decline of Actinomycetales. While the establishment of the strain AM depended on the PAH presence, the inoculation with this strain produced an early increase of Rhizobiales, independently of the phenanthrene presence.