In Depth characterization of HC-degradation CAPAcities of marine sediment microbial communities: adaptation, metabolic processes and influence of oxyGEnation regimes – DECAPAGE

Coastlines are subjected to a variety of pollution injuries from both sides, from the sea, predominantly by crude oil from shipping and offshore mining and from the land, principally through agricultural practices, urban waste waters and industrial activities. Hydrocarbon compounds and crude oil derived products are the most abundant pollutants. The damaging effects of such pollutants to the environment and human health coupled with new societal pressures make the restoration of oil-contaminated areas an urgent priority. Although they are frequently found at unacceptably high concentrations, hydrocarbons are natural compounds, and the collective catabolic diversity of microorganisms means that they can be biodegraded resulting in harmless products, thus making bioremediation an attractive option. The in situ treatment methods, which are particularly useful in remote areas where waste management and/or disposal are an issue, are applied to accelerate natural microbial processes that act on the oil. These methods include physical treatments such as mixing (also known as tilling or aeration), chemical and biological treatments using respectively chemical agents to alter the physical or chemical properties of the oil and nutrient enhancement/bioremediation. Indeed, studies have demonstrated hydrocarbon biodegradation capacities in coastal sediments (e.g. Duran and Goñi, 2010), but our understanding of the particular microbes involved, their genetic and enzymatic capacities, their interactions, as well as their functioning in the changing redox conditions, is largely unknown.
Thus, DECAPAGE will focus on microbial communities inhabiting coastal sediments, developing and applying a suite of integrated cross-disciplinary approaches to explore the hydrocarbon degradation capacities, understand the ecology of sediment ecosystems, particularly how the microbial communities degrade and/or detoxify hydrocarbons and how they are affected by the redox oscillations and alternating oxygen supply. Recently, we showed that the effect of petroleum on bacterial communities is enhanced by the presence of burrowing organisms (Stauffert et al, 2010). Indeed, the reworking activity deeply changes the bacterial communities but the overall degradation efficiency is not affected highlighting the functional redundancy involved in hydrocarbons degradation. These results rise up several important questions to understand the mechanisms underpinning the bacterial communities structuring: How microbial communities respond, adapt and degrade petroleum compounds? How the fluctuations of environmental parameters, particularly oxygen oscillations, influence this process?
The DECAPAGE project aims precisely to answer these questions characterizing in depth these bacterial communities and comparing them with those resulting from mechanical reworking that correspond to a mitigation strategy implemented during oil spills. A special interest will be made to the anoxic populations that could be strongly affected by the oxygen oscillation. At the academic point of view, the expected results will allow to understand the adaptation mechanisms driving the reorganization of bacterial communities in response to petroleum. This will help to determine the optimal oxygenation regimes for efficient petroleum degradation, crucial information for the implementation of mitigation strategies.