Impact of Petroleum Contamination on Microbial Mats

Microbial mats are well-structured bacterial communities where the different functional groups strongly interact. They develop on shorelines contaminated after oil spills and have the capacity to grow on the spilled oil. Their crude oil degradation capacity is now well established in laboratory studies, demonstrating efficient degradation of model hydrocarbon compounds. However, their in situ degradation capacities are more controversial. In many cases, it is likely that the mats are trapping oil in deeper anoxic zones, protecting the oil from abiotic transformations. In the last decade, high-throughput sequencing approaches have improved our knowledge of the biodiversity of microbial mats allowing us to describe the changes of microbial communities in response to the presence of crude oil. Many strains, belonging to all of the main functional groups found in microbial mats, have been described for their capacity to degrade oil compounds under both oxic and anoxic conditions. Their abundance significantly increases in the mats after an oil input, highlighting the potential of microbial mats for oil degradation. But microbial mats appear, in many cases, ineffective for in situ bioremediation. Nevertheless, ex situ use of mats communities for oil degradation is promising for bioremediation.