Hydrocarbon-contaminated Antarctic soil: changes in bacterial community structure during the progress of enrichment cultures with different n-alkanes as substrate

Abstract

Hydrocarbon contamination in soils from extremely cold areas, such as those from Antarctica, requires the development of specific remediation strategies for cleaning up anthropogenic pollution. Previous reports evidenced that after on-site biostimulation process of gasoil-contaminated Antarctic soils, 20% of the initial hydrocarbons remained undegraded (mainly C11–C14 n-alkanes). In the present work, these n-alkanes were added as sole carbon and energy source to enrichment cultures inoculated with the previously treated soil (biostimulation) as microorganism’s source to investigate changes occurring in the bacterial community structure. Three subcultures (8, 16, and 24 days) were performed from each enrichment culture. Changes in bacterial communities among different cultures and its subcultures were evidenced by Denaturing Gradient Gel Electrophoresis (DGGE). Results showed that even differences of one C in the alkane chain-length led to different community structures that evolved divergently from the original one. Clusters analysis showed that while samples grouped mainly by culture time, substrate-dependent differences were also evident. Isolation of biological tools for bioremediation from the cultures showed that Pseudomonadaceae members were omnipresent, whereas Rhodococcus spp. were obtained in cultures with the longest chain-length substrates. Results provided evidence about the presence of certain substrate preference of soil bacteria (even when substrates differed only in one C-atom of their chain-length), leading to different community structures. A collection of psychrotolerant hydrocarbon degrading/tolerant strains was obtained, representing a valuable tool for the design of a bioaugmentation strategy as a second, more specific stage, targeting the remnant hydrocarbons after a first bioremediation process involving biostimulation.