The vast biological and biochemical diversity of the global ocean is the driver behind marine bioprospecting for novel bioproducts. As Marine Biotechnology is gaining momentum as one of the main pillars of the ‘Brue Growth’ revolution, the ability to screen for novel compounds of interest in species with little or no genomic resources is paramount. With this respect, proteins, which are easily metabolised, can be synthetised using convenient DNA recombinant methods and can easily be modified to better meet the needs of human society, making them prized targets. Evidently, proteins that hold natural bioactivity and specificity such as toxins and other venom components, have long captured the focus of biotechnologists, leading to the merger between environmental omics and toxinology termed as ‘venomics’. Indeed, bioactive proteins such as conopeptides, conotoxins, turripeptides and others are long deemed important subjects of research. Even though current mainstream paradigms set the focus on secondary metabolites from marine organisms, transcriptomics and proteomics approaches and their combination are rising strategies for screening for thousands of proteins and peptides in non-conventional biological models, emphasising, but not limited to, marine invertebrate animals due to their abundance, biodiversity and uncanny biochemical strategies to cope with selective pressure in literally every known marine habitat. Untargeted approaches, such as RNA-Seq – based transcriptomics and tandem mass spectrometry – based proteomics, can circumvent limitations related with absent or reduced genomic annotation. The present review will outline the main contributions of ‘omics’ and computational approaches for bioprospecting for proteinaceous marine bioactives. Despite the relatively low number of ‘omics’ studies with the main purpose of discover novel compounds, there is already important literature showcasing pipelines and approaches for revolutionising the exploration of the ocean.

Most animal toxins evolved to interact with specific molecular targets, which makes them highly-prized bioactives for drug development. Marine toxins, in particular, due to their wide chemical diversity, offer a new range of possibilities, a few of which have already been translated into approved drugs. Glycera alba and Hediste diversicolor are sympatric Polychaeta with distinct ecology and behavior suspected to secrete toxins that evolved to interact with distinct molecular targets, thus with differential selectivity and potential applications in drug discovery. Comparative transcriptomics revealed that while G. alba's venom apparatus is localized in the proboscis and neurotoxins are secreted to overtake prey, H. diversicolor secretes fewer and less specific toxins that are seemingly a defense. Human interactome-directed analysis unraveled novel toxins and other bioactives with potential biomedical applications, like proteins from G. alba's venom that can regulate apoptosis, whereas H. diversicolor yielded proteins that may control inflammation and cell proliferation in humans. Omics and bioinformatics appear to be powerful tools for marine bioprospecting and drug discovery, enabling molecular mining through transcriptomes of non-model organisms and link their ecology and physiology with protein's specificity and bioreactivity. Interactome-directed analysis against the human proteome seems an efficient alternative to the design of synthetic drugs.

The current study investigates the venom-delivery system of green and red morphotypes of the sea anemone Actinia equina to disclose its potential as a source of bioactive compounds. We compared the two morphotypes using electron and optical microscopy, proteomics, and toxicity assessment on zebrafish embryos. Specialized venom-injecting cells (nematocysts) are equally distributed and found in the tentacles of both varieties. Proteomics revealed proteins of interest in both red and green Actinia, yielding the three most abundant Gene Ontology (GO) terms related to the biological processes “proteolysis”, “hemolysis in another organism” and “lipid catabolic process”. Neurotoxins and cytolytic toxins similar to known cnidarian toxins like PsTX-60A and AvTX-60A, for instance, were identified in both types. Extracts from green and red anemones were toxic to zebrafish embryos, with green anemone venom appearing to be more potent. The findings highlight the presence of proteinaceous toxins in A. equina and the potential for different varieties to possess distinct bioactive compounds. Notably, pore-forming toxins are suggested for molecular probes and immunotoxins, making them valuable assets for potential biotechnological and biomedical purposes.

To study the intricate toxicological mechanisms triggered by exposure to mixed pollutants, we exposed zebrafish embryos to legacy and emerging pollutants through binary mixtures of benzo[a]pyrene (B[a]P) and diclofenac (DFC). The combination of next-generation transcriptomics and toxicopathology disclosed instances where exposure to mixtures did not attain the expected sum of acute effects of individual toxicants, indicating potential antagonism. Despite overall higher mortality in DFC treatments, the same antagonistic trend was noted in genotoxicity and molecular pathways related to RNA turnover, cell proliferation, apoptosis and cell-cycle control. The formation of oedemas in the heart cavity and yolk sac can be an adverse outcome (AO) resulting from exposure to DFC isolated or combined, whose potential key events (KEs) may involve cell cycle arrest and apoptosis via p53 and MAPK pathways. From the findings it can be hypothesised that, rather than genotoxicity, the molecular initiating event (MIE) maybe inflammation triggered by oxidative stress. Nonetheless, the exact role of ROS in the process needs further clarification. Impaired eye function by action of DFC and B[a]P combined may be another AO, in the case caused by ocular degeneration following the suppression of biologic processes and molecular functions involved in eye development and its functionalities, possibly linked to hindered regulation of the expression of hsf4 and cryaa. Altogether, toxicopathology suggests predominance of antagonistic effects, but its integration with mechanism suggests that interactions between DFC and B[a]P in environmentally-relevant concentrations that may lead to hindrance of key functions such as the control of inflammation and cell cycle. These outcomes suggest potentially severe implications for health and survival, in case of prolonged chronic exposure to combined toxicants.

Alizarin is an anthraquinone red dye from natural or synthetic sources, widely used in textiles. Effluents of this activity can contain residual dyes, which may contaminate the aquatic environment. Studies report alizarin's aquatic toxicity, mutagenic, and carcinogenic effects. This study aimed to complement the aquatic toxicity evaluation and confirm its ability to cause genotoxicity in alternative models. Acute toxicity was performed with crustaceans, mussels, and fish embryos, while chronic toxicity was assessed in algae. Light effects on toxicity were evaluated using Daphnia similis . Histopathological effects on the gonads of Mytilus galloprovincialis and somatic mutations and sperm genotoxicity in Parhyale hawaiensis were investigated. Mutagenicity was confirmed using a miniaturized Ames test. The effect concentration 50% (EC ₅₀ ) for D. similis was 90.3, 105, and 68.6 μg L ⁻¹ for photoperiod (16 h light:8 h dark), light and dark, respectively. For Danio rerio embryos, the lethal concentration 50% (LC ₅₀ ) was 45.8 μg L ⁻¹ , and an EC ₁₀ of 20.8 μg L ⁻¹ was calculated for sublethal effects. In vivo exposures caused alterations in the digestive gland and gonads of M. galloprovincialis , even in a short‐term exposure, and increased the frequency of micronuclei and DNA damage in hemocytes and spermatozoids, respectively, of P. hawaiensis . It was mutagenic in the miniaturized Ames test using strain TA1537 (10% and 30% S9). Alizarin can be classified as a Category 1 acute aquatic toxicity according to the globally harmonized system (GHS). Due to adverse histopathological and DNA effects on reproductive systems in model organisms, it is considered a potential germ cell mutagen.

The immense biodiversity of marine invertebrates makes them high-value targets for the prospecting of novel bioactives. The present study investigated proteinaceous toxins secreted by the skin and proboscis of Glycera alba (Annelida: Polychaeta), whose congenerics G. tridactyla and G. dibranchiata are known to be venomous. Proteomics and bioinformatics enabled the detection of bioactive proteins that hold potential for biotechnological applications, including toxins like glycerotoxins (GLTx), which can interfere with neuromuscular calcium channels and therefore have value for the development of painkillers, for instance. We also identified proteins involved in the biosynthesis of toxins. Other proteins of interest include venom and toxin-related bioactives like cysteine-rich venom proteins, many of which are known to interfere with the nervous system. Ex vivo toxicity assays with mussel gills exposed to fractionated protein extracts from the skin and proboscis revealed that fractions potentially containing higher-molecular-mass venom proteins can exert negative effects on invertebrate prey. Histopathology, DNA damage and caspase-3 activity suggest significant cytotoxic effects that can be coadjuvated by permeabilizing enzymes such as venom metalloproteinases M12B. Altogether, these encouraging findings show that venomous annelids are important sources of novel bioactives, albeit illustrating the challenges of surveying organisms whose genomes and metabolisms are poorly understood.