Exploring Tetraselmis chui microbiomes-functional metagenomics for novel catalases and superoxide dismutases

The focus on microalgae for applications in several fields, e.g. resources for biofuel, the food industry, cosmetics, nutraceuticals, biotechnology, and healthcare, has gained increasing attention over the last decades. In this study, we investigate the microbiome of the cultured microalga Tetraselmis chui (T. chui) to highlight their potential for health benefits. In this context, biomolecules like antioxidants play a crucial role in the well-being of living organisms as they metabolise harmful reactive oxygen species (ROS) to reduce oxidative stress. Impaired processing of ROS leads to damaged cells and increases the risk of cancer, inflammatory diseases, and diabetes, among others. Here, we identify, characterise, and test bacterial antioxidants derived from the T. chui microbiome metagenome dataset. We identified 258 genes coding for proteins with potential antioxidant activity. Of those, four novel enzymes are expressed and identified as two superoxide dismutases (SOD), TcJM_SOD2 and TcIK_SOD3, and two catalases (CAT), TcJM_CAT2 and TcIK_CAT3. Extensive analyses characterised all implemented enzymes as active even in concentrations down to 25 ng*ml^-1 for the SODs and 15 ng*ml^-1 for the CATs. Furthermore, sequence-based analyses assign TcJM_SOD2 and TcIK_SOD3 to iron superoxide dismutases (Fe SODs) and TcJM_CAT2 and TcIK_CAT3 to heme-containing catalases. These candidates are phylogenetically classified within the phylum Pseudomonadota. Regarding the biotechnological potential, a toxicity assay did not indicate any harmful effects. The introduced enzymes may benefit medical applications and expand the potential of microalgae microbiomes. KEY POINTS: • Omics-based discoveries of antioxidant enzymes from Tetraselmis chui microbiome • Two superoxide dismutases and two catalases are identified and tested for activity • Enzyme sensitivity highlights biotechnological potential of microalgae microbiomes.