Bacterial communities of contaminated soil and microcosms

Bioremediation is a promising technology for the treatment of hydrocarbon (HC) contaminated soilsthat is based on the biodegradation capacities of native or introduced microbial populations.Biotractability tests are essential for choosing the optimal bioremediation treatment. For thispurpose, multiple microcosm tests, based on biostimulation by landfarming or bioventing andaddition of nutrients, were conducted for 120 days on a soil contaminated by diesel, after assessingits intrinsic catabolic potential. An additional bioaugmentation treatment was performed for further60 days by inoculating selected HC degrading bacteria. HC (C10-C40) concentration was monitoredby GC-FID analysis and the bacterial community evolution was analyzed by Illumina-MiSeqsequencing. The contaminated soil was dominated by Acidobacteria, Actinobacteria,Alphaproteobacteria and contained high diversity of potential HC degrading genera. The bacterialcommunities in microcosms after 120 days of biostimulation respond to bioremediation treatmentwith a shift on the composition. The main changes observed were an increase of Actinobacteria,Betaproteobacteria and Alphaproteobacteria in bioventing microcosms, while TM7 andGammaproteobacteria increased in landfarming treatment. Higher abundance of HC degradinggenera was detected in both microcosm types in respect to the untreated soil, mainly in landfarming.Approximately 40% of HC was removed after 180 days of sequential bioremediation applications.Longer incubation and finer tuning of nutrients could bring to a more effective reduction ofpollutants, encouraging the HC degrading bacteria and increasing the biodegradation efficiency.