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Marine-derived Bioactive Compounds: A Promising Frontier against Multidrug-resistant Microbial Infections.

The global escalation of Multidrug-Resistant (MDR) bacterial infections poses a serious and growing threat to public health, contributing to increased morbidity, mortality, and substantial economic burden worldwide. The widespread and often indiscriminate use of antibiotics in clinical and agricultural settings has accelerated the emergence of resistance, significantly diminishing the efficacy of conventional antimicrobial therapies. This pressing challenge necessitates the exploration of alternative sources for novel antibiotics. Marine ecosystems-renowned for their immense biodiversity and ecological complexity-have gained attention as a rich and largely untapped reservoir of bioactive natural products with potent antimicrobial activity. Marine organisms, such as sponges, tunicates, algae, and bacteria and fungi derived from marine sources, produce structurally diverse and pharmacologically active metabolites, including peptides, polyketides, alkaloids, terpenoids, sterols, lactones, and halogenated compounds. Many of these marine-derived molecules possess unique chemical scaffolds and novel mechanisms of action, offering the potential to circumvent existing resistance pathways. Some compounds have shown promising activity against MDR pathogens, including Staphylococcus aureus, Pseudomonas aeruginosa, and Acinetobacter baumannii. However, challenges such as low natural abundance, difficulty in cultivation, and structural complexity have limited their clinical translation. Recent advancements in marine biotechnology, genomics, metagenomics, and synthetic biology have opened new avenues for the discovery, biosynthesis, and structural optimization of these compounds. These innovative approaches not only facilitate sustainable production but also enhance the pharmacological properties.

Humans

Marine endophytes: biosynthetic engines for novel bioactive metabolites.

Marine endophytes are prolific sources of structurally diverse secondary metabolites with significant pharmaceutical potential, including anticancer, antimicrobial, and antioxidant agents. However, their commercial utilization is hindered by genomic instability in axenic cultures and inconsistent metabolite yields. While current studies focus on symbiotic interactions and compound discover, critical gaps persist in harnessing their biosynthetic capabilities. This review synthesizes knowledge on marine fungal metabolites and proposes a paradigm shift toward resource-driven research. It addresses strain improvement limitations and suggests strategies like mutagenesis, protoplast fusion, and metabolic engineering to bolster production stability and efficiency. The paper also discusses biological process optimization, including fermentation tuning, inducer and precursor addition, and adsorbent use, to enhance natural product synthesis. By identifying these research gaps and proposing a strategic roadmap, the review advances the stable and scalable production of bioactive metabolites, unlocking the commercial and therapeutic potential of marine endophytic fungi.

bioactive metabolites

Comparative characterization of six teleost piscidins reveals distinct antimicrobial, antibiofilm and stability profiles.

Piscidins are cationic α-helical antimicrobial peptides (AMPs) that constitute a key component of the innate immune defense of teleost fish, yet the relationship between their genomic organization, structural properties, and functional specialization remains incompletely understood. In this study, six piscidin peptides from Epinephelus akaara, Seriola dumerili, Thunnus maccoyii, Argyrosomus regius, Dicentrarchus labrax, and Epinephelus coioides were characterized through an integrated sequence-to-function approach combining comparative genomics, structural modeling, physicochemical analysis, and in vitro validation, with the aim of identifying candidates with potential for biomedical and biotechnological applications. All genes studied exhibited the conserved four-exon, three-intron architecture characteristic of teleost piscidins. Structural modeling and circular dichroism confirmed α-helical conformations under membrane-mimetic conditions, despite measurable differences in hydrophobicity, charge distribution, and predicted membrane insertion parameters. Antimicrobial assays revealed distinct functional profiles: Sd_FI25 and Epinecidin_1 displayed broad antibacterial activity against Gram-positive and Gram-negative pathogens, whereas Dl_FI22 showed selective activity with reduced temporal persistence associated with lower peptide stability. Ea_FF25 exhibited comparatively weak antibacterial potency. Antibiofilm activity varied among peptides and did not uniformly parallel planktonic MIC values. Computational predictions further suggested antiviral and antitumoral potential for several sequences, extending their prospective relevance beyond classical antibacterial roles. Conserved genomic architecture and α-helical structure coexist with pronounced functional diversification among teleost piscidins. These findings demonstrate that integrating structural prediction with experimental validation is an effective strategy for identifying fish-derived innate immune peptides as candidates for biomedical applications.

Antimicrobial activity

Discovery, biosynthesis, and bioactivities of peptidic natural products from marine sponges and sponge-associated bacteria.

Covering 2010 to 2025Sponges are benthic, sessile invertebrate metazoans that are some of the most prolific sources of natural products in the marine environment. Sponge-derived natural products are often endowed with favorable pharmaceutical bioactivities, and paired with their structural complexity, have long served as title compounds for chemical syntheses. Sponges are holobionts, in that the sponge host is associated with symbiotic and commensal microbiome. Natural products isolated from sponges can be produced by the sponge host, or the associated microbiome. Recent genomic studies have shed light on the sponge eukaryotic host as the true producer of several classes of sponge-derived peptidic natural products. In this review spanning years 2010-2025, we describe peptidic natural products isolated from the sponge hosts and the associated microbiome, detail their biosynthetic processes where known, and offer forward looking insights into future innovation in discovery and biosynthesis of peptidic natural products from marine sponges.

Porifera

Metagenomic insights and biosynthetic potential of Candidatus Entotheonella symbiont associated with Halichondria marine sponges.

Korea, being surrounded by the sea, provides a rich habitat for marine sponges, which have been a prolific source of bioactive natural products. Although a diverse array of structurally novel natural products has been isolated from Korean marine sponges, their biosynthetic origins remain largely unknown. To explore the biosynthetic potential of Korean marine sponges, we conducted metagenomic analyses of sponges inhabiting the East Sea of Korea. This analysis revealed a symbiotic association of Candidatus Entotheonella bacteria with Halichondria sponges. Here, we report a new chemically rich Entotheonella variant, which we named Ca. Entotheonella halido. Remarkably, this symbiont makes up 69% of the microbial community in the sponge Halichondira dokdoensis. Genome-resolved metagenomics enabled us to obtain a high-quality Ca. E. halido genome, which represents the largest (12 Mb) and highest quality among previously reported Entotheonella genomes. We also identified the biosynthetic gene cluster (BGC) of the known sponge-derived Halicylindramides from the Ca. E. halido genome, enabling us to determine their biosynthetic origin. This new symbiotic association expands the host diversity and biosynthetic potential of metabolically talented bacterial genus Ca. Entotheonella symbionts.IMPORTANCEOur study reports the discovery of a new bacterial symbiont Ca. Entotheonella halido associated with the Korean marine sponge Halichondria dokdoensis. Using genome-resolved metagenomics, we recovered a high-quality Ca. E. halido MAG (Metagenome-Assembled Genome), which represents the largest and most complete Ca. Entotheonella MAG reported to date. Pangenome and BGC network analyses revealed a remarkably high BGC diversity within the Ca. Entotheonella pangenome, with almost no overlapping BGCs between different MAGs. The cryptic and genetically unique BGCs present in the Ca. Entotheonella pangenome represents a promising source of new bioactive natural products.

Animals

Integration of genome mining and HiTES reveals secondary metabolic potential in marine-derived Aspergillus sp. WHUF0304.

AIMS: Marine-derived Aspergillus species are prolific producers of bioactive secondary metabolites, yet the majority of their biosynthetic gene clusters (BGCs) remain silent. This study aimed to integrate genome mining with high-throughput elicitor screening (HiTES) to unlock the metabolic potential of Aspergillus sp. WHUF0304 and identify elicitors that promote the accumulation of previously undetected metabolites. METHODS AND RESULTS: A high-quality genome of Aspergillus sp. WHUF0304 was assembled and annotated using multiple functional databases, revealing substantial secondary metabolic potential. antiSMASH analysis identified diverse BGCs, including NRPS/indole-related clusters potentially associated with indole diketopiperazine biosynthesis. A HiTES-inspired elicitor screening strategy was then applied to evaluate 42 small molecules for their ability to alter the metabolite profile of this strain. Among the tested elicitors, fluconazole was identified as the optimal inducer, triggering the production of several indole diketopiperazine-related differential metabolites. Subsequent activity-guided isolation led to the identification of a bioactive indole diketopiperazine dimer, cristatumin E, which exhibited antibacterial activity against Escherichia coli and Bacillus subtilis with minimum inhibitory concentrations (MICs) of 32 µg mL-1 and 256 µg mL-1, respectively. CONCLUSIONS: These findings demonstrate that integrating genomic and functional approaches effectively activates silent BGCs in marine fungi. The fluconazole-associated accumulation and subsequent isolation of cristatumin E, a bioactive indole diketopiperazine dimer, highlight the potential of elicitor-mediated activation to expand the detectable metabolite profile of Aspergillus sp. WHUF0304.

Aspergillus

Discovery and characterization of multifunctional bioactive peptides from Alaska Pollock (Gadus chalcogrammus) milt: hybrid in silico, in vitro, and proteomic approaches.

The growing demand for multifunctional bioactive peptides has sparked interest in underutilized marine by-products as sustainable bioresources. This study explored Alaska Pollock (Gadus chalcogrammus) milt protein as a novel source of peptides with anti-inflammatory, anti-hypertensive, and anti-diabetic effects. Protein composition was analyzed via LC-MS, followed by in silico digestion and bioactivity prediction. Molecular docking identified peptides targeting DPP-IV, α-glucosidase, ACE, GLP-1 receptor, COX-2, MuRF1, and the 20S proteasome. Among the candidates, a promising peptide (CLPPH) was synthesized and validated in vitro, demonstrating inhibitory effects on nitric oxide production, DPP-IV, ACE, and α-glucosidase. These results highlight CLPPH's potential as a multifunctional bioactive peptide and support the valorization of Alaska Pollock milt as a sustainable source for functional foods and nutraceutical applications.

Animals

Coating materials enhance urochordate primary cell culture adherence.

Marine invertebrate cell cultures are a potential source for diverse biotechnological applications, given the wide range of bioactive compounds they synthesize and accumulate. Yet, the number of established marine invertebrate cell culture systems remains limited compared with those of insects and vertebrates, particularly with respect to adherent cell cultures. Here we studied the in vitro adherence of circulating blood cells from the colonial ascidian Botryllus schlosseri. Two experimental approaches were employed, seeding blood cells either alone (setup 1) or in combination with tissue fragments (setup 2), using three basal media (DMEM, DMEM/F-12, RPMI) on culture plates coated with either Poly-L/D-lysine, gelatin, collagen, or laminin. Each experiment lasted for up to 3 d. Setup 1 results reveal that Botryllus cells remain viable and can adhere to coated surfaces in all tested media. Collagen- and laminin-coated plates supported longer-term cultures, whereas Poly-D (or L)-lysine coatings were more suitable for short-term studies. Among the basal media, RPMI and DMEM/F12 most effectively supported cell attachment. Setup 2 plates consistently showed higher cell adherence compared to setup 1, suggesting that tissue-derived factors may enhance attachment. Overall, circulating Botryllus cells demonstrate the capacity for substrate adhesion in vitro, offering a foundation for the development of adherent cell cultures.

Animals

Characterization of Dapalides D and E and Genomic Comparison of the Two Co-Occurring Dapalide-Producing Dapis spp.

Marine cyanobacteria are a rich source of diverse bioactive natural products, targeting proteins involved in many diseases. Here, we combined metagenomic analysis to enhance the structure elucidation process of two new cyclodepsipeptides named dapalides D (1) and E (2) from a collection of a cyanobacterial mat containing multiple Dapis species from Guam. Dapalides D/E are composed of 11 amino acids, including multiple identical units with different configurations. Enantioselective amino acid identification of the acid hydrolyzate established the identity of amino acids, including the configuration of α/β-stereogenic centers. Identification and analysis of the dapalides D/E biosynthetic gene cluster from a metagenome-assembled genome aided the elucidation of α-configuration and establishment of the order of individual building blocks, collectively revealing the total structure. Phylogenomic analysis indicates that the dapalides D/E producer belongs to Dapis sp. (Dapis sp. VPG23-80 MAG-2), which shares a 95.2% average nucleotide identity with Dapis sp. VPG23-80 MAG-1, the producer of dapalides A-C that cooccurs in the same assemblage. Dapalide D (1) showed moderate growth inhibitory activity against various cancer cell lines. This work expands the dapalide structure class and further highlights the use of combined chemical and metagenomic analyses for natural product structure elucidation.

Cyanobacteria

Whole-genome analysis of Brevibacterium sanguinis AZMABM HM27: a bacterial isolate from the sea anemone Radianthus magnifica and exhibiting promising multi-therapeutic properties.

BACKGROUND: The marine anemone Radianthus magnifica harbors symbiotic microbes with promising biomedical potential, yet their diversity and therapeutic properties remain underexplored. This study aimed to characterize a symbiotic bacterium isolated from R. magnifica collected from Samalona Island, Indonesia, and to evaluate its multi-therapeutic potential. METHODS: Strain AZMABM HM27 was characterized using whole-genome sequencing, functional annotation, biosynthetic gene cluster prediction, molecular docking, and in vitro bioactivity assays. RESULTS: Phylogenetic and genome-based analyses confirmed AZMABM HM27 as Brevibacterium sanguinis, with an OrthoANI value of 97.37% and a dDDH value of 76.50% against the type strain. The genome comprises a 3,834,082 bp chromosome encoding 3,362 protein-coding genes, including 95 genes involved in secondary metabolite biosynthesis. Five biosynthetic gene clusters were predicted, including those associated with ectoine, terpene, and siderophore production. The crude extract demonstrated antioxidant activity (IC₅₀ = 0.87 mg/mL), anti-inflammatory activity (up to 60% inhibition), antidiabetic activity through α-glucosidase inhibition (up to 40% inhibition), and dose-dependent antiproliferative activity against MCF-7 breast cancer cells (74.10% viability at 1 mg/mL). Molecular docking identified a lead compound, 8,9,9,10,10,11-hexafluoro-4,4-dimethyl-3,5-dioxatetracyclo [5.4.1.0(2,6)0.0(8,11)] dodecane, with strong binding affinities to selected therapeutic targets. CONCLUSIONS: B. sanguinis AZMABM HM27 represents a marine symbiotic strain associated with R. magnifica and a promising source of bioactive compounds with antioxidant, anti-inflammatory, antidiabetic, and antiproliferative potential. Further purification, structural elucidation, and in vivo studies are warranted to validate its therapeutic potential.

Animals

Growth response of the marine blue-green alga, Gomphosphaeria aponina, to inorganic nutrients and significance to management of Florida red tide.

A bioactive isolate from the blue-green alga Gomphosphaeria aponina is cytolytic towards the dinoflagellate, Gymnodinium breve, Florida's red tide organism. Batch and continuous cultures of G. aponina were used to determine nutrient limitation and to optimize mass-culture conditions. Iron and inorganic carbon were growth limiting; first-order saturation kinetics were observed for both substrates. For Fe3+, kinetic parameters were: Ks = 62 +/- 9 microgram 1(-1), and Ke max = 2.14 days-1. Maximum growth was observed at 150 micrograms Fe3+1(-1), with minimal growth below 10 microgram 1(-1). Cells colonized with increasing Fe3+ supplements, and time to reach maximum culture populations was inversely related to the concentration. For HCO3-,Ks = 62 +/- 4 mg1(-1) and Ke max = 1.3 day-1. Additions of NH4+ up to 200 micrograms 1(-1) were not stimulatory, whereas at 1.0 mg 1(-1) levels, Ke was 50% greater than for NO3- enriched medium. Concentrations greater than 25 micrograms PO4(3-) 1(-1) were stimulatory. However, at 1 mg1(-1), growth was less than in controls. Comparison of similar data available for G. breve would suggest that the inorganic nutrient requirements of G. aponina were minimal. Potential for natural control of G. breve by G. aponina is perhaps related to the efficiency of contact of the two organisms.

Animals

Canalesolide A, a Structurally Unique Polyhydroxy Macrolide from the Marine Cyanobacterium Okeania sp. with Potent Antitrypanosomal Activity.

The discovery of structurally novel natural products remains central to expanding biologically relevant chemical space, particularly within underexplored marine metabolite classes. Herein, we report the discovery and complete structural elucidation of canalesolide A, a new polyhydroxylated macrolide isolated from the marine cyanobacterium Okeania sp. The compound was identified through an integrated workflow combining phenotypic screening against Trypanosoma brucei and LC-MS/MS-based molecular networking, enabling rapid prioritization of bioactive fractions and dereplication of known metabolite families. Spectroscopic analysis revealed that canalesolide A belongs to the bastimolide-related class of macrolides but exhibits a distinct structural architecture. Its structure was established by integrating ultrahigh-resolution NMR spectroscopy, empirical configurational analysis of polyol systems, targeted model compound synthesis, and controlled chemical degradation and derivatization. This combined strategy resolved stereochemical motifs that were inaccessible by direct analysis of the intact macrolide alone, providing a transferable approach for assigning densely oxygenated marine macrolides. Genome mining identified the putative biosynthetic gene cluster and proposed biosynthetic pathway for a bastimolide-related macrolide. Canalesolide A displays potent, low nanomolar antitrypanosomal activity against human-infective subspecies of T. brucei with rapid elimination of parasites within 1 h at 1 μM. Although moderate mammalian cytotoxicity was observed, preliminary in vivo efficacy/toxicity studies in infected mice suggest a narrow therapeutic window highlighting the need for improved selectivity. This study expands the structural and biosynthetic diversity of polyhydroxylated macrolides and establishes a generalizable framework for resolving stereochemically complex natural products.

Macrolides

Artificial intelligence for anticancer drug discovery from natural products of macroalgae and sponges: A systematic review.

Marine natural products (MNPs) from macroalgae and marine sponges have inspired clinically important anticancer agents, including the cytarabine pharmacophore and the eribulin scaffold, while cyanobacterial dolastatin chemistry supplies the auristatin payloads of several marine-inspired antibody-drug conjugates (ADCs) such as brentuximab vedotin. Artificial intelligence (AI) methods, encompassing both classical machine learning (ML) with hand-engineered features and modern deep learning (DL) with many-layered neural networks, are increasingly supporting key decisions in natural-product anticancer drug discovery, including bioactivity prediction, target identification, absorption, distribution, metabolism, excretion and toxicity (ADMET) filtering, generative analogue design, and the selection of preclinical candidates. DL architectures relevant to this field include graph neural networks, transformer-based molecular generators, diffusion models for protein-ligand docking, and convolutional networks for mass spectrometry, while classical ML contributes interpretable fingerprint-based bioactivity models and molecular networking for dereplication. This review follows a systematic literature review methodology to organize the landscape of AI methods now applied to MNP anticancer discovery, distinguishing ML and DL approaches where relevant, situating them within the chemical context of macroalgal and sponge-derived oncology leads, and critically examining published case studies, including validation level (computational, in vitro, in vivo, clinical). The principal bottleneck for medical translation has shifted partly from algorithmic capability toward data infrastructure and experimental validation. Sparse, heterogeneous, and taxonomically biased bioactivity records limit what current models can learn and reduce the reliability of AI-prioritized candidates entering the preclinical pipeline. A roadmap is proposed that prioritizes open MNP-specific benchmarks, symbiont-aware modeling, and active learning loops with synthesizability and ADMET constraints. These AI workflows may accelerate the prioritization of marine-derived anticancer leads and support earlier, more evidence-based translational decisions in oncology drug development.

Biological Products

Rhodococcus dendrobeaniae sp. nov., an actinomycete isolated from an Arctic marine invertebrate exhibiting cytotoxic activity, and an emended description of Rhodococcus sovatensis.

A polyphasic study was conducted to establish the taxonomic status of strain T060T, an orange, aerobic, coccoid and non-motile actinomycete, isolated from a marine bryozoan (Dendrobeania sp.) collected in the Barents Sea. Phylogenetic analysis of the 16S rRNA gene sequences revealed Rhodococcus sovatensis DSM 102881T as the closest related species to strain T060T with a similarity of 99.54%. Phylogenomic analysis confirmed a close relationship between T060T and R. sovatensis DSM 102881T, while supporting their distinction. Digital DNA-DNA hybridization and average nucleotide identity values between strain T060T and R. sovatensis DSM 102881T were 26.4 and 84.3%, respectively, supporting the delineation of the isolate as a new species. Genomic characterization of the assembled genomes of T060T and R. sovatensis DSM 102881T showed genome sizes of 5.3 and 4.2 Mbp, with a G + C content of 64.38 and 65.01%, respectively. Genome analysis of strain T060T identified 15 biosynthetic gene clusters (BGCs) with low sequence similarity to known BGCs, indicating its capacity to produce unknown, potentially bioactive secondary metabolites. Furthermore, growth of T060T in eight different media revealed condition-dependent cytotoxic activity. The strongest cytotoxicity was observed for fractionated extracts from T060T grown in half-strength ISP 2 with filtered seawater against the human malignant cell lines MCF7 and A2058, and to a lesser extent against the non-malignant MRC5 cell line, highlighting its biotechnological potential. Based on the data from polyphasic taxonomy studies, it is proposed that strain T060T be classified in the genus Rhodococcus as Rhodococcus dendrobeaniae sp. nov. Additionally, the acquired data of R. sovatensis were used to amend its original description.

Rhodococcus

Divergent Lineage of Terpene Synthases Establishes Terpenoid Biosynthesis in Brown Macroalgae.

Brown algae of the order Dictyotales uniquely stand out among stramenopiles (heterokonts) as prolific producers of bioactive terpenoid molecules associated with chemical defense and antifouling. Although more than 200 sesquiterpenoids and diterpenoids have been reported, largely from the genera of Dictyota and Dictyopteris, their biosynthetic origin has remained unknown for decades. Leveraging de novo genome and transcriptome sequencing in the nonmodel alga Dictyota coriacea, we identified a brown algal-specific lineage of type I terpene synthases (TSs) that harbors novel catalytic motifs distinct from those characterized in plants, microbes, red algae, and metazoans. Across three brown algal species, we characterized 15 terpene synthases, including DcTS-2, which produces the diterpene alcohol dilophol, a proposed biosynthetic intermediate to the antifouling metabolite pachydictyol A. X-ray crystal structures of the monoterpene synthase DcTS-3 further revealed that the brown algal enzymes retain the canonical terpene synthase fold, and together with mutagenesis studies, suggest the catalytic role of the novel motifs defining this newly established evolutionary lineage. Brown algal terpene synthases separate into two subgroups, with mono- and diTSs containing putative chloroplast-targeting sequences while sesquiTSs lack them, suggesting convergent compartmentalization of terpene biosynthesis with land plants. Together, these findings establish the molecular basis of terpenoid biosynthesis in brown algae and highlight the challenges of adapting established biosynthetic logic to nonmodel marine algae.

Alkyl and Aryl Transferases