7 - Bacteria-mediated remediation: Restoring polycyclic aromatic hydrocarbon (PAHs) contaminated marine ecosystems

Abstract

Pollution caused by polycyclic aromatic hydrocarbons (PAHs) is considered a threat to the environment as it is toxic, carcinogenic, and mutagenic, affecting almost every living organism and its surroundings. PAH toxicity increases as their molecular weight rises. Due to their hydrophobic nature, such recalcitrant hydrocarbons settle down in the coastal environment. The marine ecosystem is severely affected by the toxicity created by various PAHs as it has become one of the main reservoirs of petroleum hydrocarbons. Sources of hydrocarbon contamination are discharge from petroleum industries, transportation of oil through ships, accidental oil spills, and dismantling ships at the shore, which allow the PAHs to enter the oceans and contaminate the coastal region. The adverse effect of PAHs not only kill marine organisms, but the PAHs also enter the food chain, which can cause severe health issues in humans. So, there is a constant need to remediate contaminated marine ecosystems. PAH remediation procedures employing physical and chemical modes are being used to ensure PAH-free surroundings. However, these solutions and their byproducts themselves come with their own side effects and give rise to new pollutants. Bioremediation is therefore considered a holistic approach to clean up the environment's contaminated areas. Bacteria-mediated degradation is one of the most enticing, effective, and ecofriendly bioremediation approaches. Under this, PAH breakdown occurs using a single microorganism or a consortium that consumes these pollutants as a carbon source and mineralizes these harmful molecules completely or partially into less hazardous forms. Thus, bacterial-based remediation has emerged as a prominent strategy to combat PAH contamination in coastal areas.