Alicycliphilus: current knowledge and potential for bioremediation of xenobiotics

Alicycliphilus is a promising candidate for participating in the development of novel xenobiotics bioremediation processes. Members of the Alicycliphilus genus are environmental bacteria mostly found in polluted sites such as landfills and contaminated watercourses, and in sewage sludges from wastewater treatment plants. They exhibit a versatile metabolism and the ability to use oxygen, nitrate and chlorate as terminal electron acceptors, which allow them to biodegrade xenobiotics under oxic or anoxic conditions. Pure cultures of Alicycliphilus strains are able to biodegrade some pollutants such as industrial solvents (acetone, cyclohexanol and N-methylpyrrolidone), aromatic hydrocarbons (benzene, toluene and anthracene), as well as polyurethane varnishes and foams, and they can even transform Cr(VI) to Cr(III). In addition, Alicycliphilus has also been identified in bacterial communities involved in wastewater treatment plants for denitrification, and the degradation of emerging pollutants such as triclosan, nonylphenol, N-heterocyclic aromatic compounds (indole and quinoline), and antibiotics (tetracycline and oxytetracycline). This work summarizes the current knowledge on the Alicycliphilus genus, describing its different metabolic characteristics, focusing on its xenobiotic biodegradation abilities and examining the distinct pathways and molecular bases that sustain them. We also discuss the progress made in genetic manipulation and 'omics' analyses, as well as Alicycliphilus participation in novel bioremediation strategies.