Comparative bioaugmentation with a consortium and a single strain in a phenanthrene-contaminated soil: Impact on the bacterial community and biodegradation

• We studied two soil bioaugmentation strategies, using a PAH-degrading strain and consortium.
• The isolated strain exhibited highest efficiency to improve PAH degradation.
• Pyrosequencing showed that bacterial community was highly modified by both inocula.
• The isolated strain caused more drastic changes on soil microbial community.
• The sequencing results revealed the usefulness of DGGE as a rapid screening method.

The efficiency of two inoculation strategies, using a consortium (CON) or an isolated strain (AM), on phenanthrene-contaminated soil was determined with special concern on the study of the bacterial community composition by PCR-DGGE and pyrosequencing of 16S rRNA gene fragments.Both strategies stimulated the phenanthrene degradation, increasing the cultivable heterotrophic bacteria number and biological activity. At the end of the treatments, the microcosms inoculated with AM reached the lowest values of phenanthrene but also the lowest dehydrogenase activity.In DGGE patterns a reduction in number of bands in the contaminated and inoculated microcosms was observed, being the most significant differences attributed to inoculation with AM.The pyrosequencing technique yielded results that correlated with the fingerprint, showing that the bacterial community composition based on relative abundance was significantly modified by treatments.Sphingomonadales and Burkholderiales were highly stimulated by phenanthrene contamination and inoculation. In the Phe microcosm, the higher increase in Actinomycetales (mainly Arthrobacter) was observed.Effectively, the use of the strain AM as inoculant became the best strategy to remediate the soil mainly based on the degradation efficiency, however it caused more drastic changes in microbial community than inoculation with CON, what can be compromising the ulterior functionality of the soil.