Abstract
Antarctica is an attractive target for human exploration and scientific investigation, however the negative effects of human activity on this continent are long lasting and can have serious consequences on the native ecosystem. Various areas of Antarctica have been contaminated with diesel fuel, which contains harmful compounds such as heavy metals and polycyclic aromatic hydrocarbons (PAH). Bioremediation of PAHs by the activity of microorganisms is an ecological, economical, and safe decontamination approach. Since the introduction of foreign organisms into the Antarctica is prohibited, it is key to discover native bacteria that can be used for diesel bioremediation. By following the degradation of the PAH phenanthrene, we isolated 53 PAH metabolizing bacteria from diesel contaminated Antarctic soil samples, with three of these isolates exhibiting a high phenanthrene degrading capacity. In particular, the Sphingobium xenophagum D43FB isolate showed the highest phenanthrene degradation ability, generating up to 95% degradation of initial phenanthrene. D43FB can also degrade phenanthrene in the presence of its usual co-pollutant, the heavy metal cadmium, and showed the ability to grow using diesel-fuel as a sole carbon source. Microtiter plate assays and SEM analysis revealed that S. xenophagum D43FB exhibits the ability to form biofilms and can directly adhere to phenanthrene crystals. Genome sequencing analysis also revealed the presence of several genes involved in PAH degradation and heavy metal resistance in the D43FB genome. Altogether, these results demonstrate that S. xenophagum D43FB shows promising potential for its application in the bioremediation of diesel fuel contaminated-Antarctic ecosystems.
Highlights
The southernmost continent in Earth, Antarctica, is a unique territory that plays an important role in the earth’s climate, and a source of many natural resources
To first test the ability of phenanthrene to enrich for polycyclic aromatic hydrocarbons (PAH) degrading bacteria, total bacterial growth in Antarctic soil samples was tested when supplemented with glucose or phenanthrene and compared with a non-supplemented control
Antarctica is a region in which the introduction of foreign organisms is forbidden, a good understanding of the available native bacteria available to bioremediate contaminated Antarctic areas, as well as a good comprehension of their metabolizing power and the mechanisms underlying PAH degradation will be key in the development of more efficient decontamination strategies
Summary
The southernmost continent in Earth, Antarctica, is a unique territory that plays an important role in the earth’s climate, and a source of many natural resources These characteristics have fueled the interest of many countries to explore and investigate this region, leading to the involvement of over 30 nations in scientific research, and the establishment of more than a Phenanthrene Degrading Bacteria from Antarctica. Oil contamination can generate detrimental changes in soil properties, including modifications in maximum surface temperature, pH, and carbon and nitrogen levels (Aislabie et al, 2004) These physical and chemical changes promote rearrangements in the soil bacterial communities as well, with Proteobacteria from Burkholderia, Sphingomonas and specially Pseudomonas species heavily dominating over bacteria from Bacteroidetes, Cyanobacteria, Acidobacteria, Actinobacteria, Chloroflexi, Gemmatimonadetes, Verrucomicrobia, and other phyla which compose the normal inhabitants non-polluted Antarctic soils. This results in a significant decrease in species richness and evenness, and a large decline in soil biodiversity of contaminated soils (Saul et al, 2005; van Dorst et al, 2014, 2016)
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