Pathways and functional enzyme-mediated mechanisms of tetracycline biodegradation by the marine microalgae Phaeodactylum tricornutum.

The widespread use of tetracycline and its consequent aquatic pollution pose significant risks to environmental and human health. Recently, microalgae have been demonstrated as a promising, environmentally friendly and non-chemical way to reduce tetracycline levels; however, biodegradation pathways and mechanisms remain elusive. Consequently, this study systematically investigated the pathways and functional enzyme-mediated mechanisms of tetracycline biodegradation by a marine model algal species (Phaeodactylum tricornutum). The results revealed that P. tricornutum exhibits reasonable physiological adaptation and tolerance to tetracycline exposure through cellular homeostasis and the activation of energy reallocation. Simultaneously, P. tricornutum was able to biodegrade tetracycline (e.g., 88.4% of a 4 mg/L tetracycline solution). It was also proposed that this diatom degrades tetracycline via C-N bond cleavage of metallo-beta-lactamase, demethylation by cytochrome P450, deamination by cytochrome P450 and ornithine cyclodeaminase, oxygenation by flavin adenine dinucleotide (FAD)-dependent monooxygenase, reduction and ring-opening by antibiotic biosynthesis monooxygenase. This study provides multidimensional theoretical and empirical support for addressing antibiotic pollution in aquatic ecosystems.