Studies of Saudi Arabia halophilic and non-halophilic bacteria that degrade the highly complex polycyclic aromatic hydrocarbon pollutant benzo[a]pyrene

Oil-related industry remains central to the economy of the Kingdom of Saudi Arabia (KSA), as a result, the contamination of the environment with petroleum pollutants is common, and among them, are polycyclic aromatic hydrocardons (PAHs). One of the promising strategies to remove these pollutants is bioremediation, which is the exploitation of micro-organisms to use pollutants as substrates for their growth. PAHs consist of 2-5 rings, and the higher the number of ring, the more difficult is its biodegradation. Benzo(a)pyrene (BZP) is a 5-ring-containing PAH, which has proven to be more recalcitrant to biodegradation, and well-characterised BZP-degrading bacteria have not been reported yet from KSA. The current project proposes to identify, isolate and characterise halophilic and non-halophilic bacteria from the KSA that can efficiently degrade BZP, and to test the bioremediation potential of these bacteria in removing this pollutant from contaminated soil. To achieve this goal, oil-contaminated soil samples from the shoreline of the Arabian Gulf will be used to enrich in vitro cultures, in the presence of BZP as a sole source of carbon, which will lead to the isolation of BZP-degrading bacteria. Thereafter, using 16S rRNA sequencing and phylogenic analyses, bacterial species will be identified, and further studies will be carried out to assess bacterial ability to utilise BZP in various conditions of pH (3, 5,6,7, 8 and 9), temperature (30, 35, 37.5, 40, 45, 50 oC) and salinity (0, 2, 4 and 6% NaCl). For halophilic bacteria, salinity up to 20% NaCl will be tested. The second step of the project will be to quantify the utilisation of BZP, and to propose possible biochemical pathways of BZP degradation in these bacteria using gas chromatography and mass spectrometry (GC-MS). The third step of our work will be to assess the bioremediation potential of these bacteria in removing BZP, and other PAHs, in contaminated soil samples, in laboratory scale. This bioremediation investigation will also be extended to other bacteria (pyrene-, phenanthrene- and anthracene-degrading bacteria) that were isolated as part of our previous projects. Overall, this project will not only lead to the isolation and characterisation of BZP-degrading bacteria, but it will also contribute in generating data that will form the basis of the development of PAH-degrading bacteria as bioremediation products.