Metagenomic Insights into Environmental Microbiome and Their Application in Food/Pharmaceutical Industry

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.

Microalgae in Terms of Biomedical Technology: Probiotics, Prebiotics, and Metabiotics

Green, red, brown, and diatomic algae, as well as cyanobacteria, have been in the focus of attention of scientists and technologists for over 5 decades. This is due to their importance as efficient and economical producers of food additives, cosmetics, pharmaceuticals, biofertilizers, biofuels, and wastewater bioremediation agents. Recently, the role of microalgae has increasingly been considered in terms of their probiotic function, i.e., of their ability to normalize the functioning of the microbiota of humans and agricultural animals and to produce biologically active substances, including hormones, neurotransmitters, and immunostimulators. A separate brief subsection of the review deals with the potential functions of microalgae with respect to the brain and psyche, i.e., as psychobiotics. Moreover, algal polysaccharides and some other compounds can be broken down to short fragments that will stimulate the development of useful intestinal microorganisms, i.e., function as efficient prebiotics. Finally, many components of microalgal cells and chemical agents produced by them can exert important health-promoting effects per se, which indicates that they are as potentially valuable metabiotics (the term preferred by late Prof. B.A. Shenderov), which are alternatively denoted as postbiotics in the literature.

Probiotics and Psychobiotics: the Role of Microbial Neurochemicals

In light of recent data, microorganisms should be construed as organisms that are capable of communication and collective behaviors. Microbial communication signals are involved both in interactions among microbial cells within microbial social systems, including the human body-inhabiting microconsortium, and the dialog between the microbiota and the host organism. The microbiota inhabits various niches of the host organism, especially the gastrointestinal (GI) tract. Microorganisms release diverse signal molecules and, in addition, specifically respond to host signals. This enables them to constantly interact with the nervous system including the brain and the immune system of the host organism. Evolutionarily conserved signals that are involved in the communication between microbiota and the host include neuroactive substances (neurochemicals) such as peptides, amino acids, biogenic amines, short-chain fatty acids, and gaseous substances. This ongoing dialog may either stabilize the host's physical and mental health state or, alternatively, cause serious health problems. Attempts are made to correct imbalances in the brain-gut-microbiota axis with probiotics including their subgroup called psychobiotics that release neuroactive substances directly influencing the human brain, psyche, and behavior. A number of recent review works address the microbiota-host system and its communication signals. Some of the publications focus on the involvement of neurochemicals in the bidirectional communication within the host-microbiota system. However, this work concentrates on the impact of bacterial cell components, metabolites, and signal molecules as promising alternatives to the currently widespread probiotics that have both advantages and disadvantages. Such biologically active agents of microbial origin are referred to as postbiotics or, alternatively, metabiotics (the term preferred in this work).