Chemistry, biosynthesis and biological activity of terpenoids and meroterpenoids in bacteria and fungi isolated from different marine habitats

Bacillus haimaensis sp. nov.: a novel cold seep-adapted bacterium with unique biosynthetic potential

Deep-sea cold seeps harbor unique microbial communities that play crucial roles in biogeochemical cycles and possess potential biotechnological applications. Herein, we report the isolation, characterization, and genomic analysis of a novel Bacillus species, Bacillus haimaensis sp. nov. (type strain CSS-39T, CCTCC M20241382), obtained from sediments collected at a depth of 1,350 m in the Haima cold seep, South China Sea. Phylogenomic analysis, revealing an average nucleotide identity of 87.78% and a digital DNA-DNA hybridization value of 34.0% with its closest relative B. tianshenii DSM 25879T, confirms the taxonomic novelty of the genus Bacillus. The complete 4.54 Mb genome of B. haimaensis reveals adaptations to the cold seep environment, including enhanced nutrient acquisition capabilities and stress response mechanisms. Comparative genomic analysis identifies 27 unique gene clusters related to spore germination and sulfate assimilation, suggesting specialized metabolic strategies for this extreme habitat. Furthermore, six biosynthetic gene clusters, including a novel lassopeptide cluster, indicate a potential for secondary metabolite production. Phenotypic characterization demonstrates the strain's ability to utilize diverse carbon sources and tolerate a wide range of environmental conditions. Our findings provide insights into microbial adaptations to deep-sea cold seeps and highlight the potential of B. haimaensis for biotechnological applications in bioremediation and natural product discovery. This study expands our understanding of microbial diversity in extreme marine environments and offers a new model bacterium for investigating bacterial adaptations to deep-sea ecosystems.IMPORTANCEThe discovery of Bacillus haimaensis sp. nov. in the Haima cold seep of the South China Sea represents a significant advancement in our understanding of microbial adaptations to extreme marine environments. This novel species exhibits remarkable metabolic versatility and unique genomic features, providing insights into bacterial survival strategies in nutrient-variable, high-pressure deep-sea ecosystems. Comprehensive genomic analysis reveals distinctive biosynthetic gene clusters, suggesting untapped potential for discovering novel natural product. Furthermore, B. haimaensis exhibits promising capabilities for aromatic compound degradation, indicating potential applications in marine bioremediation. This work not only expands our knowledge of microbial diversity in understudied deep-sea habitats but also highlights the biotechnological promise of extremophiles. The adaptive mechanisms elucidated in B. haimaensis, particularly those related to sporulation and sulfate assimilation, contribute to our broader understanding of microbial ecology in cold seeps and may inform future research on climate change impacts on deep-sea ecosystems.

Identification of SIRT3 modulating compounds in deep-sea fungi metabolites: Insights from molecular docking and MD simulations

SIRT3, a crucial deacetylase that plays a key role in regulating mitochondrial acetylation, is tightly linked to metabolic processes and is essential for the maintenance of eukaryotic life. SIRT3 is a potential therapeutic target due to its key role in various diseases, including ageing, heart disease, cancer, and metabolic disorders. In this work, we aimed to identify potential SIRT3 inhibitors from the deep-sea fungal metabolites by employing molecular docking and ADMET analysis. Based on the binding affinities, ten compounds were selected whose docking scores were in the range of -9.693 to -8.327 kcal/mol. Further, four compounds Penipanoid C, Penicillactam, Quinolonimide, and Brevianamide R were selected based on the ADMET properties and subjected to Molecular dynamics simulations to assess the stability of these molecules with target. The stability analysis indicated that the selected compounds could act as lead compounds during in vitro assays to advance these drug candidates towards clinical drug development.

Marine Natural Products in Inflammation-Related Diseases: Opportunities and Challenges

In recent decades, the potentiality of marine natural products (MNPs) in the medical field has been increasingly recognized. Natural compounds derived from marine microorganisms, algae, and invertebrates have shown significant promise for treating inflammation-related diseases. In this review, we cover the three primary sources of MNPs and their diverse and unique chemical structures and bioactivities. This review aims to summarize the progress of MNPs in combating inflammation-related diseases. Moreover, we cover the functions and mechanisms of MNPs in diseases, highlighting their functions in regulating inflammatory signaling pathways, cellular stress responses, and gut microbiota, among others. Meanwhile, we focus on key technologies and scientific methods to address the current limitations and challenges in MNPs.

Newly isolated terpenoids (covering 2019-2024) from Aspergillus species and their potential for the discovery of novel antimicrobials

The rapid emergence of drug-resistant microbial pathogens has posed challenges to global health in the twenty-first century. This development has significantly made most antibiotics ineffective in the treatment of infections they cause, resulting in increasing treatment costs and annual death rates. To address the challenge posed by these pathogens, we explore the potential of secondary metabolites from Aspergillus species as a source of new and effective therapeutic agents to treat drug-resistant infections. Terpenoids, a distinct group of natural products, are extensively distributed in plants and fungi, and have been attributed with significant antibacterial, anticancer, and antiviral activities. In this review, we present an overview of Aspergillus species, and review the novel terpenoids isolated from them from 2019 to April 2024, highlighting anti-infective activity against members of the ESKAPE pathogens. We further focus on the strategies through which the structural framework of these new terpenoids could be modified and/or optimized to feed a pipeline of new lead compounds targeting microbial pathogens. Overall, this review provides insight into the therapeutic applications of terpenoids sourced from Aspergillus species and the potential for the discovery of new compounds from these fungi to combat antimicrobial resistance.

What Factors Determine the Brevione B Desaturation Mechanism in the Nonheme Iron Dioxygenase BrvJ?

The natural product synthesis of brevione J undergoes a cascade of reactions including an oxidative desaturation and a ring-expansion. The C1-C2 desaturation of brevione B is catalyzed by the nonheme iron dioxygenase BrvJ using one molecule of O2 and α-ketoglutarate (αKG). However, whether the subsequent oxidative ring expansion reaction is also catalyzed by the same enzyme is unknown and remains controversial. To gain insight into the mechanism of brevione J biosynthesis a computational study is reported here using molecular dynamics and density functional theory approaches. The work predicts that both cycles can proceed in the same protein structure on an iron center with O2 and αKG for each cycle. The rate-determining step is a hydrogen atom abstraction step in both reaction cycles. Interestingly, the OH rebound barriers are high in energy in cycle 1 due to stereochemical interactions and substrate positioning that enable an efficient desaturation reaction.

Heterologous Biosynthesis of Terpenoids in Saccharomyces cerevisiae

Terpenoids are widely distributed in nature and have various applications in healthcare products, pharmaceuticals, and fragrances. Despite the significant potential that terpenoids possess, traditional production methods, such as plant extraction and chemical synthesis, face challenges in meeting current market demand. With the advancement of synthetic biology and metabolic engineering, it becomes feasible to construct efficient microbial cell factories for large-scale production of terpenoids. This article primarily centers on the heterologous expression of terpenoids in Saccharomyces cerevisiae, detailing the expression of terpenoid biosynthesis pathways through the utilization of cellular microcompartments, strategies for the efficient expression of key P450 enzymes in the synthesis pathway, and the regulation and optimization of host metabolism to enhance flux to terpenoids synthesis. Additionally, we analyze current challenges and propose solutions to further refine yeast chassis for more effective terpenoids production.

Streptomyces yaizuensis sp. nov., a berninamycin C-producing actinomycete isolated from sponge

While screening for antibiotics in a marine sample, we discovered a berninamycin C-producing actinomycete, designated YSPA8T, isolated from a sponge. A polyphasic approach was used to determine the taxonomic position of the strain. Strain YSPA8T formed sympodially branched aerial mycelia that ultimately segment into chains of spores. Comparative and phylogenetic analyses of the 16S rRNA gene sequence showed that strain YSPA8T were closely related to Streptomyces clavuligerus ATCC 27064T (99.66%), Streptomyces amakusaensis NRRL B-3351T (98.69%), Streptomyces inusitatus NBRC 13601T (98.48%), and 'Streptomyces jumonjinensis' JCM 4947 (98.41%). The phylogenetic tree using the 16S rRNA gene sequences, and both phylogenomic trees suggested that the closest relative of strain YSPA8T was S. clavuligerus ATCC 27064T. The average nucleotide identity, digital DNA-DNA hybridization, and average amino acid identity values between strain YSPA8T and S. clavuligerus ATCC 27064T were 84.1%, 28.9%, and 82.5%, respectively, which were below the thresholds of 95%, 70%, and 95% for a prokaryotic conspecific assignment. The G + C of the strain YSPA8T was 72.6%. Whole-cell hydrolysates of strain YSPA8T contained LL-diaminopimelic acid. The predominant menaquinones were MK-9(H6) (49%) and MK-9(H8) (48%), and the major fatty acids were C16:0 (26.8%), C16:1 ω7c/ω6c (17.2%), iso-C16:0 (16.0%), and iso-C15:0 (12.5%). The major phospholipids were diphosphatidylglycerol, phosphatidylethanolamine, and other unidentified phospholipids. Based on the phenotypic, phylogenetic, genomic, and chemotaxonomic data, strain YSPA8T represents a novel species of the genus Streptomyces, and the proposed name for this species is Streptomyces yaizuensis sp. nov. The type strain is YSPA8T (=NBRC 115866T = TBRC 17196T).

A new anthraquinone derivative from the marine fish-derived fungus Alternaria sp. X112

A new anthraquinone, altermodinacid A (1), and five known derivatives, pachybasic acid (2), emodic acid (3), emodin (4), phomarin (5), and 1,7-dihydroxy-3-methylanthracene-9,10-dione (6), were discovered from a halotolerant fungus Alternaria sp. X112 isolated from a marine fish Gadus macrocephalus. Their structures were determined by analysing MS and NMR data. The cytotoxic effect, antiagricultural pathogens activity, antibacterial activity and quorum sensing inhibitory potential of new compound 1 were evaluated.

Biosynthesis of a bacterial meroterpenoid reveals a non-canonical class II meroterpenoid cyclase

Meroterpenoids are hybrid natural products that arise from the integration of terpenoid and non-terpenoid biosynthetic pathways. While the biosynthesis of fungal meroterpenoids typically follows a well-established sequence of prenylation, epoxidation, and cyclization, the pathways for bacterial perhydrophenanthrene meroterpenoids remain poorly understood. In this study, we report the construction of an engineered metabolic pathway in Streptomyces for the production of the bacterial meroterpenoid, atolypene A (1). Our research reveals a novel biosynthetic pathway wherein the structure of 1 is assembled through a distinct sequence of epoxidation, prenylation, and cyclization, divergent from its fungal counterparts. We demonstrate that the noncanonical class II meroterpenoid cyclase (MTC) AtoE initiates cyclization by protonating the epoxide via the E314 residue, which acts as a Brønsted acid within the characteristic xxxE314TAE motif. Additionally, bioinformatic analysis of biosynthetic gene clusters (BGCs) that contain AtoE-like MTCs supports that bacteria have the potential to produce a wide array of meroterpenoids.

Terpenoids, a Rising Star in Bioactive Constituents for Alleviating Food Allergy: A Review about the Potential Mechanism, Preparation, and Application

Food allergies affect approximately 2.5% of the global population, with a notable increase in prevalence observed each year. Terpenoids, a class of natural bioactive constituents, have been widely utilized in the management of immune- and inflammation-related disorders, and their potential in alleviating food allergies is increasingly being recognized. This article summarizes various terpenoids derived from plant, fungal, and marine sources. Among them, triterpenoids, such as oleanolic acid, ursolic acid, and lupeol, possess the highest proportion and bioactivity in alleviating food allergy. Additionally, the mechanisms by which terpenoids may mitigate allergic diseases were categorically outlined, focusing on their roles in epithelial mucosal barrier function, immunomodulatory effects during the sensitization phase, inhibition of effector cells, oxidative stress, and regulation of microbial homeostasis. Finally, the advantages and limitations of natural extraction and artificial synthesis methods were compared, and the application of terpenoids in the food industry were also discussed. This article serves as a useful reference for the development of methods or functional foods based on terpenoids, which could represent a promising avenue for alleviating food allergy.

Discovery of Bioactive Terpenes Derived from a Polar Fungus

Polar fungi play a vital role as prolific sources of unique chemical structures and diverse bioactive compounds. Eutypella sp. D-1 is a fungus isolated from the Arctic, and six compounds were extracted from the fermentation broth. Their structures are elucidated from HRESIMS, NMR spectroscopy, and ECD calculations. Compounds 1-5 are newly discovered compounds, with compound 1 possessing a rare peroxide-bridge structure. Compounds 1-4 are categorized as pimarane-type diterpenes, while compounds 5 and 6 belong to the eudesmanolide sesquiterpenes. Compound 4 demonstrates anti-inflammatory activity by inhibiting lipopolysaccharide-induced nitric oxide release in RAW264.7 cells. Compounds 4 and 5 show antibacterial activity against Escherichia coli and Staphylococcus aureus.

Comprehensive genome analysis of two novel Saccharopolyspora strains-Saccharopolyspora montiporae sp. nov. and Saccharopolyspora galaxeae sp. nov. isolated from stony corals in Hainan

Marine actinomycetes exhibit a high level of biodiversity and possess significant potential for the production of high-value secondary metabolites. During the course of investigation of marine actinobacteria from corals, two Saccharopolyspora strains, namely, HNM0983T and HNM0986T, were isolated from stony corals collected from the coastal area of Hainan Island. The 16S ribosomal RNA (rRNA) gene sequence analysis revealed that these two strains are putative novel taxa of the genus Saccharopolyspora. Whole-genome sequencing comparisons further confirmed the two strains as belonging to two novel Saccharopolyspora species, which can be distinguished phenotypically and chemically from their current closest phylogenetic relatives. Some genomic information of the genus Saccharopolyspora was compared for evaluating the production capacity of secondary metabolites. A total of 519 biosynthetic gene clusters (BGCs) from the genus Saccharopolyspora were used for analysis, and terpene BGCs were found to be widespread and most abundant in this genus. In addition, abundant novel BGCs in the genus Saccharopolyspora are not clustered with the known BGCs in the database, indicating that the metabolites of the genus Saccharopolyspora deserve further exploration. On the basis of these presented results, Saccharopolyspora montiporae sp. nov. (type strain = HNM0983T = CCTCC AA 2020014T = KCTC 49526T) and Saccharopolyspora galaxeae sp. nov. (type strain = HNM0986T = CCTCC AA 2020011T = KCTC 49524T) are proposed as the names for the new strains, respectively.

Regioselective synthesis of 2-aminophenols from N-arylhydroxylamines

A novel strategy for the synthesis of 2-aminophenols in the absence of metals and oxidants was described. The 2-aminophenols were efficiently obtained through a cascade [3,3]-sigmatropic rearrangement and in situ hydrolysis process by using readily available N-arylhydroxylamines and the in situ-generated methyl chlorosulfonate from commercially available sulfuryl chloride and methanol under mild conditions. This method could be scaled up and has a wide substrate scope with great functional group tolerance and high regioselectivity. The 2-aminophenol products could be readily converted into structurally diverse functional molecules in good yields under various conditions.

Datasets of fungal diversity and pseudo-chromosomal genomes of mangrove rhizosphere soil in China

With climate change and anthropic influence on the coastal ecosystems, mangrove ecosystems are disappearing at an alarming rate. Accordingly, it becomes important to track, study, record and store the mangrove microbial community considering their ecological importance and potential for biotechnological applications. Here, we provide information on mangrove fungal community composition and diversity in mangrove ecosystems with different plant species and from various locations differing in relation to anthropic influences. We describe twelve newly assembled genomes, including four chromosomal-level genomes of fungal isolates from the mangrove ecosystems coupled with functional annotations. We envisage that these data will be of value for future studies including comparative genome analysis and large-scale temporal and/or spatial research to elucidate the potential mechanisms by which mangrove fungal communities assemble and evolve. We further anticipate that the genomes represent valuable resources for bioprospecting related to industrial or clinical uses.

Recent Advances in Marine-Derived Compounds as Potent Antibacterial and Antifungal Agents: A Comprehensive Review

The increase in antimicrobial resistance (AMR) in microorganisms is a significant global health concern. Various factors contribute to AMR, including alterations in cell membrane permeability, increased efflux pump activity, enzymatic modification or inactivation of antibiotics, target site changes, alternative metabolic pathways, and biofilm formation. Marine environments, with their extensive biodiversity, provide a valuable source of natural products with a wide range of biological activities. Marine-derived antimicrobial compounds show significant potential against drug-resistant bacteria and fungi. This review discusses the current knowledge on marine natural products such as microorganisms, sponges, tunicates and mollusks with antibacterial and antifungal properties effective against drug-resistant microorganisms and their ecological roles. These natural products are classified based on their chemical structures, such as alkaloids, amino acids, peptides, polyketides, naphthoquinones, terpenoids, and polysaccharides. Although still in preclinical studies, these agents demonstrate promising in vivo efficacy, suggesting that marine sources could be pivotal in developing new drugs to combat AMR, thereby fulfilling an essential medical need. This review highlights the ongoing importance of marine biodiversity exploration for discovering potential antimicrobial agents.

A Close View of the Production of Bioactive Fungal Metabolites Mediated by Chromatin Modifiers

Secondary metabolites produced by fungi are well known for their biological properties, which play important roles in medicine. These metabolites aid in managing infections and treating chronic illnesses, thereby contributing substantially to human health improvement. Despite this extensive knowledge, the vast biodiversity and biosynthetic potential of fungi is still largely unexplored, highlighting the need for further research in natural products. In this review, several secondary metabolites of fungal origin are described, emphasizing novel structures and skeletons. The detection and characterization of these metabolites have been significantly facilitated by advancements in analytical systems, particularly modern hyphenated liquid chromatography/mass spectrometry. These improvements have primarily enhanced sensitivity, resolution, and analysis flow velocity. Since the in vitro production of novel metabolites is often lower than the re-isolation of known metabolites, understanding chromatin-based alterations in fungal gene expression can elucidate potential pathways for discovering new metabolites. Several protocols for inducing metabolite production from different strains are discussed, demonstrating the need for uniformity in experimental procedures to achieve consistent biosynthetic activation.

Discovery of Kebanmycins with Antibacterial and Cytotoxic Activities from the Mangrove-Derived Streptomyces sp. SCSIO 40068

Mangrove derived actinomycetes are a rich reservoir of bioactive natural products and play important roles in pharmaceutical chemistry. In a screen of actinomycetes from mangrove rhizosphere sedimental environments, the isolated strain Streptomyces sp. SCSIO 40068 displayed strong antibacterial activity. Further fractionation of the extract yielded four new compounds kebanmycins A-D (1-4) and two known analogues FD-594 (5) and the aglycon (6). The structures of 1-6 were determined based on extensive spectroscopic data and single-crystal X-ray diffraction analysis. 1-3 featured a fused pyranonaphthaxanthene as an integral part of a 6/6/6/6/6/6 polycyclic motif, and showed bioactivity against a series of Gram-positive bacteria and cytotoxicity to several human tumor cells. In addition, the kebanmycins biosynthetic gene cluster (keb) was identified in Streptomyces sp. SCSIO 40068, and KebMT2 was biochemically characterized as a tailoring sugar-O-methyltransferase, leading to a proposed biosynthetic route to 1-6. This study paves the way to further investigate 1 as a potential lead compound.

Genome Mining Reveals a UbiA-Type Prenyltransferase Access to Farnesylation of Diketopiperazines

UbiA-type prenyltransferases (PTases) are significant enzymes that lead to structurally diverse meroterpenoids. Herein, we report the identification and characterization of an undescribed UbiA-type PTase, FtaB, that is responsible for the farnesylation of indole-containing diketopiperazines (DKPs) through genome mining. Heterologous expression of the fta gene cluster and non-native pathways result in the production of a series of new C2-farnesylated DKPs. This study broadens the reaction scope of UbiA-type PTases and expands the chemical diversity of meroterpenoids.

Regulatory functions of homeobox domain transcription factors in fungi

Homeobox domain (HD) proteins present a crucial involvement in morphological differentiation and other functions in eukaryotes. Most HD genes encode transcription factors (TFs) that orchestrate a regulatory role in cellular and developmental decisions. In fungi, multiple studies have increased our understanding of these important HD regulators in recent years. These reports have revealed their role in fungal development, both sexual and asexual, as well as their importance in governing other biological processes in these organisms, including secondary metabolism, pathogenicity, and sensitivity to environmental stresses. Here, we provide a comprehensive review of the current knowledge on the regulatory roles of HD-TFs in fungi, with a special focus on Aspergillus species.

Bacteria-targeted magnolol-loaded multifunctional nanocomplexes for antibacterial and anti-inflammatory treatment

Natural plant-derived small molecules have shown great potential for their antimicrobial and anti-inflammatory properties. In this study, we successfully developed a nanocomplex consisting of magnolol (Mag), a surfactant with an 18 carbon hydrocarbon chain and multi-amine head groups (C18N3), and a peptide (cyclic 9-amino acid peptide (CARG)) with targeting capabilities forStaphylococcus aureus(S. aureus). The obtained Mag/C18N3/CARG nanocomplexes exhibited strong antibacterial activity againstS. aureus. Furthermore, they demonstrated anti-inflammatory effects by reducing the secretion of pro-inflammatory cytokines such as TNF-α, IL-6, and IL-1βfrom macrophage inflammatory cells. This was achieved through downregulating the activation of NF-κB, KEAP1, and NRF2 signaling pathways. In a murine skin infection model, the Mag/C18N3/CARG nanocomplexes effectively suppressed the growth ofS. aureusin the infected area and promoted wound healing. Additionally, in a mouse model of acute kidney injury (AKI), the nanocomplexes significantly reduced the levels of blood urea nitrogen and creatinine, leading to a decrease in mortality rate. These findings demonstrate the potential of combining natural plant-derived small molecules with C18N3/CARG assemblies as a novel approach for the development of effective and safe antibacterial agents.

Genome-resolved metagenomics of Venice Lagoon surface sediment bacteria reveals high biosynthetic potential and metabolic plasticity as successful strategies in an impacted environment

Bacteria living in sediments play essential roles in marine ecosystems and deeper insights into the ecology and biogeochemistry of these largely unexplored organisms can be obtained from 'omics' approaches. Here, we characterized metagenome-assembled-genomes (MAGs) from the surface sediment microbes of the Venice Lagoon (northern Adriatic Sea) in distinct sub-basins exposed to various natural and anthropogenic pressures. MAGs were explored for biodiversity, major marine metabolic processes, anthropogenic activity-related functions, adaptations at the microscale, and biosynthetic gene clusters. Starting from 126 MAGs, a non-redundant dataset of 58 was compiled, the majority of which (35) belonged to (Alpha- and Gamma-) Proteobacteria. Within the broad microbial metabolic repertoire (including C, N, and S metabolisms) the potential to live without oxygen emerged as one of the most important features. Mixotrophy was also found as a successful lifestyle. Cluster analysis showed that different MAGs encoded the same metabolic patterns (e.g., C fixation, sulfate oxidation) thus suggesting metabolic redundancy. Antibiotic and toxic compounds resistance genes were coupled, a condition that could promote the spreading of these genetic traits. MAGs showed a high biosynthetic potential related to antimicrobial and biotechnological classes and to organism defense and interactions as well as adaptive strategies for micronutrient uptake and cellular detoxification. Our results highlighted that bacteria living in an impacted environment, such as the surface sediments of the Venice Lagoon, may benefit from metabolic plasticity as well as from the synthesis of a wide array of secondary metabolites, promoting ecosystem resilience and stability toward environmental pressures.

Supplementary Information

The online version contains supplementary material available at 10.1007/s42995-023-00192-z.

Microbiome variation at the clam-sediment interface may explain changes in local productivity of Chamelea gallina in the North Adriatic sea

BACKGROUND

The clam Chamelea gallina is an ecologically and economically important marine species in the Northwestern Adriatic Sea, which currently suffers from occasional, and still unexplained, widespread mortality events. In order to provide some glimpses in this direction, this study explores the connections between microbiome variations at the clam-sediment interface and the nutritional status of clams collected at four Italian production sites along the Emilia Romagna coast, with different mortality incidence, higher in the Northern sites and lower in the Southern sites.

RESULTS

According to our findings, each production site showed a peculiar microbiome arrangement at the clam-sediment interface, with features that clearly differentiate the Northern and Southern sites, with the latter also being associated with a better nutritional status of the animal. Interestingly, the C. gallina digestive gland microbiome from the Southern sites was enriched in some health-promoting microbiome components, capable of supplying the host with essential nutrients and defensive molecules. Furthermore, in experiments conducted under controlled conditions in aquaria, we provided preliminary evidence of the prebiotic action of sediments from the Southern sites, allowing to boost the acquisition of previously identified health-promoting components of the digestive gland microbiome by clams from the Northern sites.

CONCLUSIONS

Taken together, our findings may help define innovative microbiome-based management strategies for the preservation of the productivity of C. gallina clams in the Adriatic Sea, through the identification and maintenance of a probiotic niche at the animal-sediment interface.

Synthesis and application of a compound microbial inoculant for effective soil remediation

Currently, there is a noticeable scarcity of applications that harness composite microbial inoculants to stimulate straw decomposition, nitrogen fixation, and crop growth. This study addresses this gap by selecting and coculturing three bacterial strains to create a composite microbial inoculant named HY-1. This innovative inoculant exhibits multifunctional capabilities, including nitrogen fixation, straw decomposition, and crop growth promotion. Furthermore, we aimed to explore its impact on soil microbial communities. The results showed that the optimal preparation conditions for the compound microbial inoculant HY-1 were 28.5 ± 0.6 °C, pH = 7.34 ± 0.40, and bacteriophage ratio 1:2:1 (Microbacterium: Streptomyces fasciatus: Bacillus amyloliquefaciens). Compared to single strains, the combination exhibited higher levels of cellulose-degrading and nitrogen-fixing enzyme activity, increased the straw degradation rate by 37.91% within 180 days, and significantly promoted the growth of corn seedlings. Under the condition of straw return, the compound bio-fungicide HY-1 effectively improved the soil microbial diversity. At that time, the soil had the highest number of unique bacterial operational taxonomic units (166), and the abundance of Proteobacteria in the soil increased by 7.24%, while that of Acidobacteriota decreased by 2.27%. The biosynthetic function of the cell wall/membrane/periplasm and the metabolic function of transporting inorganic ions were significantly enhanced. In this study, we discovered that employing coculturing techniques to produce the composite microbial inoculant HY-1 and applying it in the field effectively compensates for the limitations of single-strain inoculants, which often exhibit fewer functions and less pronounced effects. This approach demonstrates significant potential for enhancing the quality of agricultural soils.

Anticancer Activity of Natural Products and Related Compounds

Nature has always been a precious source of bioactive molecules which are used for the treatment of various diseases [...].

Biochar-assisted degradation of oxytetracycline by Achromobacter denitrificans and underlying mechanisms

Contamination of the environment with large amounts of residual oxytetracycline (OTC) and the corresponding resistance genes poses a potential threat to natural ecosystems and human health. In this study, an effective OTC-degrading strain, identified as Achromobacter denitrificans OTC-F, was isolated from activated sludge. In the degradation experiment, the degradation rates of OTC in the degradation systems with and without biochar addition were 95.01-100% and 73.72-99.66%, respectively. Biochar promotes the biodegradation of OTC, particularly under extreme environmental conditions. Toxicity evaluation experiments showed that biochar reduced biotoxicity and increased the proportion of living cells by 17.36%. Additionally, biochar increased the activity of antioxidant enzymes by 34.1-91.0%. Metabolomic analysis revealed that biochar promoted the secretion of antioxidant substances such as glutathione and tetrahydrofolate, which effectively reduced oxidative stress induced by OTC. This study revealed the mechanism at the molecular level and provided new strategies for the bioremediation of OTC in the environment.

New Insights on Biological Activities, Chemical Compositions, and Classifications of Marine Actinomycetes Antifouling Agents

Biofouling is the assemblage of undesirable biological materials and macro-organisms (barnacles, mussels, etc.) on submerged surfaces, which has unfavorable impacts on the economy and maritime environments. Recently, research efforts have focused on isolating natural, eco-friendly antifouling agents to counteract the toxicities of synthetic antifouling agents. Marine actinomycetes produce a multitude of active metabolites, some of which acquire antifouling properties. These antifouling compounds have chemical structures that fall under the terpenoids, polyketides, furanones, and alkaloids chemical groups. These compounds demonstrate eminent antimicrobial vigor associated with antiquorum sensing and antibiofilm potentialities against both Gram-positive and -negative bacteria. They have also constrained larval settlements and the acetylcholinesterase enzyme, suggesting a strong anti-macrofouling activity. Despite their promising in vitro and in vivo biological activities, scaled-up production of natural antifouling agents retrieved from marine actinomycetes remains inapplicable and challenging. This might be attributed to their relatively low yield, the unreliability of in vitro tests, and the need for optimization before scaled-up manufacturing. This review will focus on some of the most recent marine actinomycete-derived antifouling agents, featuring their biological activities and chemical varieties after providing a quick overview of the disadvantages of fouling and commercially available synthetic antifouling agents. It will also offer different prospects of optimizations and analysis to scale up their industrial manufacturing for potential usage as antifouling coatings and antimicrobial and therapeutic agents.

Distribution, abundance, and ecogenomics of the Palauibacterales, a new cosmopolitan thiamine-producing order within the Gemmatimonadota phylum

The phylum Gemmatimonadota comprises mainly uncultured microorganisms that inhabit different environments such as soils, freshwater lakes, marine sediments, sponges, or corals. Based on 16S rRNA gene studies, the group PAUC43f is one of the most frequently retrieved Gemmatimonadota in marine samples. However, its physiology and ecological roles are completely unknown since, to date, not a single PAUC43f isolate or metagenome-assembled genome (MAG) has been characterized. Here, we carried out a broad study of the distribution, abundance, ecotaxonomy, and metabolism of PAUC43f, for which we propose the name of Palauibacterales. This group was detected in 4,965 16S rRNA gene amplicon datasets, mainly from marine sediments, sponges, corals, soils, and lakes, reaching up to 34.3% relative abundance, which highlights its cosmopolitan character, mainly salt-related. The potential metabolic capabilities inferred from 52 Palauibacterales MAGs recovered from marine sediments, sponges, and saline soils suggested a facultative aerobic and chemoorganotrophic metabolism, although some members may also oxidize hydrogen. Some Palauibacterales species might also play an environmental role as N2O consumers as well as suppliers of serine and thiamine. When compared to the rest of the Gemmatimonadota phylum, the biosynthesis of thiamine was one of the key features of the Palauibacterales. Finally, we show that polysaccharide utilization loci (PUL) are widely distributed within the Gemmatimonadota so that they are not restricted to Bacteroidetes, as previously thought. Our results expand the knowledge about this cryptic phylum and provide new insights into the ecological roles of the Gemmatimonadota in the environment. IMPORTANCE Despite advances in molecular and sequencing techniques, there is still a plethora of unknown microorganisms with a relevant ecological role. In the last years, the mostly uncultured Gemmatimonadota phylum is attracting scientific interest because of its widespread distribution and abundance, but very little is known about its ecological role in the marine ecosystem. Here we analyze the global distribution and potential metabolism of the marine Gemmatimonadota group PAUC43f, for which we propose the name of Palauibacterales order. This group presents a saline-related character and a chemoorganoheterotrophic and facultatively aerobic metabolism, although some species might oxidize H2. Given that Palauibacterales is potentially able to synthesize thiamine, whose auxotrophy is the second most common in the marine environment, we propose Palauibacterales as a key thiamine supplier to the marine communities. This finding suggests that Gemmatimonadota could have a more relevant role in the marine environment than previously thought.

Homeobox transcription factor HbxA influences expression of over one thousand genes in the model fungus Aspergillus nidulans

In fungi, conserved homeobox-domain proteins are transcriptional regulators governing development. In Aspergillus species, several homeobox-domain transcription factor genes have been identified, among them, hbxA/hbx1. For instance, in the opportunistic human pathogen Aspergillus fumigatus, hbxA is involved in conidial production and germination, as well as virulence and secondary metabolism, including production of fumigaclavines, fumiquinazolines, and chaetominine. In the agriculturally important fungus Aspergillus flavus, disruption of hbx1 results in fluffy aconidial colonies unable to produce sclerotia. hbx1 also regulates production of aflatoxins, cyclopiazonic acid and aflatrem. Furthermore, transcriptome studies revealed that hbx1 has a broad effect on the A. flavus genome, including numerous genes involved in secondary metabolism. These studies underline the importance of the HbxA/Hbx1 regulator, not only in developmental processes but also in the biosynthesis of a broad number of fungal natural products, including potential medical drugs and mycotoxins. To gain further insight into the regulatory scope of HbxA in Aspergilli, we studied its role in the model fungus Aspergillus nidulans. Our present study of the A. nidulans hbxA-dependent transcriptome revealed that more than one thousand genes are differentially expressed when this regulator was not transcribed at wild-type levels, among them numerous transcription factors, including those involved in development as well as in secondary metabolism regulation. Furthermore, our metabolomics analyses revealed that production of several secondary metabolites, some of them associated with A. nidulans hbxA-dependent gene clusters, was also altered in deletion and overexpression hbxA strains compared to the wild type, including synthesis of nidulanins A, B and D, versicolorin A, sterigmatocystin, austinol, dehydroaustinol, and three unknown novel compounds.

Screening of marine sediment-derived microorganisms and their bioactive metabolites: a review

Marine sediments are one of the largest habitats on Earth, and their unique ecology, such as high salinity, high pressure, and hypoxia, may activate certain silent genes in marine microbes, resulting in microbes, enzymes, active products, and specific metabolic pathways that can adapt to these specific ecological environments. Marine sediment-derived microorganisms and their bioactive metabolites are of great significance and have potential commercial development prospects for food, pharmaceutical, chemical industries, agriculture, environmental protection and human nutrition and health. In recent years, although there have been numerous scientific reports surrounding marine sediment-derived microorganisms and their bioactive metabolites, a comprehensive review of their research progress is lacking. This paper presents the development and renewal of traditional culture-dependent and omics analysis techniques and their application to the screening of marine sediment-derived microorganisms producing bioactive substances. It also highlights recent research advances in the last five years surrounding the types, functional properties and potential applications of bioactive metabolites produced by marine sediment-derived microorganisms. These bioactive metabolites mainly include antibiotics, enzymes, enzyme inhibitors, sugars, proteins, peptides, and some other small molecule metabolites. In addition, the review ends with concluding remarks on the challenges and future directions for marine sediment-derived microorganisms and their bioactive metabolites. The review report not only helps to deepen the understanding of marine sediment-derived microorganisms and their bioactive metabolites, but also provides some useful information for the exploitation and utilization of marine microbial resources and the mining of new compounds with potential functional properties.

Recent Advances in Using Natural Antibacterial Additives in Bioactive Wound Dressings

Wound care is a global health issue with a financial burden of up to US $96.8 billion annually in the USA alone. Chronic non-healing wounds which show delayed and incomplete healing are especially problematic. Although there are more than 3000 dressing types in the wound management market, new developments in more efficient wound dressings will require innovative approaches such as embedding antibacterial additives into wound-dressing materials. The lack of novel antibacterial agents and the misuse of current antibiotics have caused an increase in antimicrobial resistance (AMR) which is estimated to cause 10 million deaths by 2050 worldwide. These ongoing challenges clearly indicate an urgent need for developing new antibacterial additives in wound dressings targeting microbial pathogens. Natural products and their derivatives have long been a significant source of pharmaceuticals against AMR. Scrutinising the data of newly approved drugs has identified plants as one of the biggest and most important sources in the development of novel antibacterial drugs. Some of the plant-based antibacterial additives, such as essential oils and plant extracts, have been previously used in wound dressings; however, there is another source of plant-derived antibacterial additives, i.e., those produced by symbiotic endophytic fungi, that show great potential in wound dressing applications. Endophytes represent a novel, natural, and sustainable source of bioactive compounds for therapeutic applications, including as efficient antibacterial additives for chronic wound dressings. This review examines and appraises recent developments in bioactive wound dressings that incorporate natural products as antibacterial agents as well as advances in endophyte research that show great potential in treating chronic wounds.

Biodegradation of polystyrene (PS) by marine bacteria in mangrove ecosystem

Plastics pollution poses a new threat to marine ecosystems. Mangrove locating at estuary worldwide is probably the most heavily polluted area trapping various plastics transported from terrestrial and nearby marine aquaculture. Expanded polystyrene (EPS) is one of most common plastic debris therein and even in the plastic garbage. Here we showed the bacterial diversity of the polystyrene-degrading microbial community from EPS waste sites from a subtropical mangrove area. After enrichment with EPS, the degradation consortia were obtained. They shared a similar community structure dominated by bacteria of Sphingomonadaceae, Rhodanobacteraceae, Rhizobiaceae, Dermacoccaceae, Rhodocyclaceae, Hyphomicrobiaceae, and Methyloligellaceae. Diverse bacteria standing for the first member of the genera of Novosphingobium, Gordonia, Stappia, Mesobacillus, Alcanivorax, Flexivirga, Cytobacillus, Thioclava, and Thalassospira showed PS degradation capability as a pure culture. Further, PS biodegradation of Gordonia sp. and Novosphingobium sp. was quantified by weight loss, in addition to obvious morphological and structural changes of the PS films observed by SEM, ATR-FTIR, and contact angle analysis. The formation of new oxygen-containing functional groups implied the degradation pathway of oxidation. Although the degradation rates ranged from 2.7% to 7.7% after one month in lab and possibly lower in situ, their role in EPS removal is unneglectable.

Marine-derived fungi as biocatalysts

Marine microorganisms account for over 90% of ocean biomass and their diversity is believed to be the result of their ability to adapt to extreme conditions of the marine environment. Biotransformations are used to produce a wide range of high-added value materials, and marine-derived fungi have proven to be a source of new enzymes, even for activities not previously discovered. This review focuses on biotransformations by fungi from marine environments, including bioremediation, from the standpoint of the chemical structure of the substrate, and covers up to September 2022.

Anti-Tumor Secondary Metabolites Originating from Fungi in the South China Sea's Mangrove Ecosystem

A mangrove is a unique ecosystem with abundant resources, in which fungi are an indispensable microbial part. Numerous mangrove fungi-derived secondary metabolites are considerable sources of novel bioactive substances, such as polyketides, terpenoids, alkaloids, peptides, etc., which arouse people's interest in the search for potential natural anti-tumor drugs. This review includes a total of 44 research publications that described 110 secondary metabolites that were all shown to be anti-tumor from 39 mangrove fungal strains belonging to 18 genera that were acquired from the South China Sea between 2016 and 2022. To identify more potential medications for clinical tumor therapy, their sources, unique structures, and cytotoxicity qualities were compiled. This review could serve as a crucial resource for the research status of mangrove fungal-derived natural products deserving of further development.

Furaquinocins K and L: Novel Naphthoquinone-Based Meroterpenoids from Streptomyces sp. Je 1-369

Actinomycetes are the most prominent group of microorganisms that produce biologically active compounds. Among them, special attention is focused on bacteria in the genus Streptomyces. Streptomycetes are an important source of biologically active natural compounds that could be considered therapeutic agents. In this study, we described the identification, purification, and structure elucidation of two new naphthoquinone-based meroterpenoids, furaquinocins K and L, from Streptomyces sp. Je 1-369 strain, which was isolated from the rhizosphere soil of Juniperus excelsa (Bieb.). The main difference between furaquinocins K and L and the described furaquinocins was a modification in the polyketide naphthoquinone skeleton. In addition, the structure of furaquinocin L contained an acetylhydrazone fragment, which is quite rare for natural compounds. We also identified a furaquinocin biosynthetic gene cluster in the Je 1-369 strain, which showed similarity (60%) with the furaquinocin B biosynthetic gene cluster from Streptomyces sp. KO-3988. Furaquinocin L showed activity against Gram-positive bacteria without cytotoxic effects.

Ecological and Oceanographic Perspectives in Future Marine Fungal Taxonomy

Marine fungi are an ecological rather than a taxonomic group that has been widely researched. Significant progress has been made in documenting their phylogeny, biodiversity, ultrastructure, ecology, physiology, and capacity for degradation of lignocellulosic compounds. This review (concept paper) summarizes the current knowledge of marine fungal diversity and provides an integrated and comprehensive view of their ecological roles in the world's oceans. Novel terms for 'semi marine fungi' and 'marine fungi' are proposed based on the existence of fungi in various oceanic environments. The major maritime currents and upwelling that affect species diversity are discussed. This paper also forecasts under-explored regions with a greater diversity of marine taxa based on oceanic currents. The prospects for marine and semi-marine mycology are highlighted, notably, technological developments in culture-independent sequencing approaches for strengthening our present understanding of marine fungi's ecological roles.

Polyhydroxyalkanoate (PHA) Biopolymer Synthesis by Marine Bacteria of the Malaysian Coral Triangle Region and Mining for PHA Synthase Genes

Polyhydroxyalkanoate (PHA), a biodegradable and plastic-like biopolymer, has been receiving research and industrial attention due to severe plastic pollution, resource depletion, and global waste issues. This has spurred the isolation and characterisation of novel PHA-producing strains through cultivation and non-cultivation approaches, with a particular interest in genes encoding PHA synthesis pathways. Since sea sponges and sediment are marine benthic habitats known to be rich in microbial diversity, sponge tissues (Xestospongia muta and Aaptos aaptos) and sediment samples were collected in this study from Redang and Bidong islands located in the Malaysian Coral Triangle region. PHA synthase (phaC) genes were identified from sediment-associated bacterial strains using a cultivation approach and from sponge-associated bacterial metagenomes using a non-cultivation approach. In addition, phylogenetic diversity profiling was performed for the sponge-associated bacterial community using 16S ribosomal ribonucleic acid (16S rRNA) amplicon sequencing to screen for the potential presence of PHA-producer taxa. A total of three phaC genes from the bacterial metagenome of Aaptos and three phaC genes from sediment isolates (Sphingobacterium mizutaii UMTKB-6, Alcaligenes faecalis UMTKB-7, Acinetobacter calcoaceticus UMTKB-8) were identified. Produced PHA polymers were shown to be composed of 5C to nC monomers, with previously unreported PHA-producing ability of the S. mizutaii strain, as well as a 3-hydroxyvalerate-synthesising ability without precursor addition by the A. calcoaceticus strain.

Indispensable role of microbes in anticancer drugs and discovery trends

Recent years have seen an increased focus on the advancement of naturally derived products for the treatment of cancer. Since the beginning of recorded history, nature has provided a variety of medicinal agents, and an overwhelming number of drugs that we have today are derived from natural sources. Such natural agents are prominently used to treat several diseases such as diabetes, malaria, Alzheimer's, pulmonary disorders, etc. with cancer being the highlight of this review. Due to the rapid development of resistance to chemotherapeutic drugs, the hunt for effective novel drugs is still a paramount concern in cancer treatment. Moreover, many chemotherapy drugs typically have high toxicity and adverse side effects, which necessitates the need to develop anti-tumor drugs that can be employed to treat deadly tumors with fewer negative effects on health and better efficacy. Isolation of several chemotherapeutic drugs has been conducted from a wide range of natural sources which include plants, microbes, fungi, and marine microorganisms. Considering the trends of previous decades, microbial diversity has grown to play a significant role in the formulation of pharmaceuticals and drugs, especially antibiotics and anti-cancer medications. Microbe-derived antitumor antibiotics such as anthracycline, epothilones, bleomycin, actinomycin, and staurosporine are amongst the widely used cancer chemotherapeutic agents. This review deals majorly with microbe-derived anticancer drugs taking into account their derivatives, mechanism of action, isolation procedures, limitations, and tumors targeted by them. This article also reports the phase of clinical study these drugs are undergoing. Moreover, it intends to portray the indispensable part that these microbes have been playing since time immemorial in the odyssey of chemotherapeutic agents. KEY POINTS: • Microbial diversity contributes heavily towards the formulation of anticancer drugs. • Polypeptides, carbohydrates, and alkaloids are prevalent microbe-based drug classes. • Microbe-derived anticancer agents target various sarcomas, carcinomas, and lymphomas.

Brasilterpenes A-E, Bergamotane Sesquiterpenoid Derivatives with Hypoglycemic Activity from the Deep Sea-Derived Fungus Paraconiothyrium brasiliense HDN15-135

Five bergamotane sesquiterpenoid derivatives, brasilterpenes A-E (1-5), bearing an unreported spiral 6/4/5 tricyclic ring system, were isolated from the deep sea-derived ascomycete fungus Paraconiothyrium brasiliense HDN15-135. Their structures, including absolute configurations, were established by extensive spectroscopic methods complemented by single-crystal X-ray diffraction analyses, electronic circular dichroism (ECD), and density-functional theory (DFT) calculations of nuclear magnetic resonance (NMR) data including DP4+ analysis. The hypoglycemic activity of these compounds was assessed using a diabetic zebrafish model. Brasilterpenes A (1) and C (3) significantly reduced free blood glucose in hyperglycemic zebrafish in vivo by improving insulin sensitivity and suppressing gluconeogenesis. Moreover, the hypoglycemic activity of compound 3 was comparable to the positive control, anti-diabetes drug rosiglitazone. These results suggested brasilterpene C (3) had promising anti-diabetes potential.

A Fungal Promiscuous UbiA Prenyltransferase Expands the Structural Diversity of Chrodrimanin-Type Meroterpenoids

Prenyltransferases play important roles in the diversification of natural products and the improvement of biological activities. A UbiA-type prenyltransferase CdnC with substrate promiscuity was identified as the pivotal builder of the noncanonical chrodrimanin skeletons, which carry a benzo-cyclohexanone structure as the nonterpene part. In vitro and heterologous expression studies with CdnC led to the production of a series of novel chrodrimanin-like structures. The discovery of CdnC offers a referable strategy for the biosynthesis and structural diversification of farnesyl-derived meroterpenoids.

Repurposing non-oncology small-molecule drugs to improve cancer therapy: Current situation and future directions

Drug repurposing or repositioning has been well-known to refer to the therapeutic applications of a drug for another indication other than it was originally approved for. Repurposing non-oncology small-molecule drugs has been increasingly becoming an attractive approach to improve cancer therapy, with potentially lower overall costs and shorter timelines. Several non-oncology drugs approved by FDA have been recently reported to treat different types of human cancers, with the aid of some new emerging technologies, such as omics sequencing and artificial intelligence to overcome the bottleneck of drug repurposing. Therefore, in this review, we focus on summarizing the therapeutic potential of non-oncology drugs, including cardiovascular drugs, microbiological drugs, small-molecule antibiotics, anti-viral drugs, anti-inflammatory drugs, anti-neurodegenerative drugs, antipsychotic drugs, antidepressants, and other drugs in human cancers. We also discuss their novel potential targets and relevant signaling pathways of these old non-oncology drugs in cancer therapies. Taken together, these inspiring findings will shed new light on repurposing more non-oncology small-molecule drugs with their intricate molecular mechanisms for future cancer drug discovery.

Genome mining methods to discover bioactive natural products

Covering: 2016 to 2021With genetic information available for hundreds of thousands of organisms in publicly accessible databases, scientists have an unprecedented opportunity to meticulously survey the diversity and inner workings of life. The natural product research community has harnessed this breadth of sequence information to mine microbes, plants, and animals for biosynthetic enzymes capable of producing bioactive compounds. Several orthogonal genome mining strategies have been developed in recent years to target specific chemical features or biological properties of bioactive molecules using biosynthetic, resistance, or transporter proteins. These "biosynthetic hooks" allow researchers to query for biosynthetic gene clusters with a high probability of encoding previously undiscovered, bioactive compounds. This review highlights recent case studies that feature orthogonal approaches that exploit genomic information to specifically discover bioactive natural products and their gene clusters.

A Chiral-Pool-Based Strategy to Access trans-syn-Fused Drimane Meroterpenoids: Chemoenzymatic Total Syntheses of Polysin, N-Acetyl-polyveoline and the Chrodrimanins

trans-syn-Fused drimane meroterpenoids are unique natural products that arise from contra-thermodynamic polycyclizations of their polyene precursors. Herein we report the first total syntheses of four trans-syn-fused drimane meroterpenoids, namely polysin, N-acetyl-polyveoline, chrodrimanin C, and verruculide A, in 7-18 steps from sclareolide. The trans-syn-fused drimane unit is accessed through an efficient acid-mediated C9 epimerization of sclareolide. Subsequent applications of enzymatic C-H oxidation and contemporary annulation methodologies install the requisite C3 hydroxyl group and enable rapid generation of structural complexity to provide concise access to these natural products.

Biotechnological potential of fungi from a mangrove ecosystem: Enzymes, salt tolerance and decolorization of a real textile effluent

The mangrove is an ecosystem bounded by the line of the largest tide in size that occurs in climatic and subtropical regions. In this environment, microorganisms and their enzymes are involved in a series of transformations and nutrient cycling. To evaluate the biotechnological potential of fungi from a mangrove ecosystem, samples from mangrove trees were collected at the Paranaguá Estuarine Complex in Brazil and 40 fungal isolates were obtained, cultivated, and screened for hydrolytic and ligninolytic enzymes production, adaptation to salinity and genetic diversity. The results showed a predominance of hydrolytic enzymes and fungal tolerance to ≤ 50 g L^-1 sodium chloride (NaCl) concentration, a sign of adaptive halophilia. Through morphological and molecular analyses, the isolates were identified as: Trichoderma atroveride, Microsphaeropsis arundinis, Epicoccum sp., Trichoderma sp., Gliocladium sp., Geotrichum sp. and Cryphonectria sp. The ligninolytic enzymatic potential of the fungi was evaluated in liquid cultures in the presence and absence of seawater and the highest activity of laccase among isolates was observed in the presence of seawater with M. arundinis (LB07), which produced 1,037 U L^-1. Enzymatic extracts of M. arundinis fixed at 100 U L^-1 of laccase partially decolorized a real textile effluent in a reaction without pH adjustment and chemical mediators. Considering that mangrove fungi are still few explored, the results bring an important contribution to the knowledge about these microorganisms, as their ability to adapt to saline conditions, biodegradation of pollutants, and enzymatic potential, which make them promising candidates in biotechnological processes.

Marine Bacterial Secondary Metabolites: A Treasure House for Structurally Unique and Effective Antimicrobial Compounds

The prevalence of antimicrobial resistance reduces the effectiveness of antimicrobial drugs in preventing and treating infectious diseases caused by pathogenic organisms, such as bacteria, fungi, and viruses. Because of the burgeoning growth of microbes with antimicrobial-resistant traits, there is a dire need to identify and develop novel and effective antimicrobial agents to treat infections from antimicrobial-resistant strains. The marine environment is rich in ecological biodiversity and can be regarded as an untapped resource for prospecting novel bioactive compounds. Therefore, exploring the marine environment for antimicrobial agents plays a significant role in drug development and biomedical research. Several earlier scientific investigations have proven that bacterial diversity in the marine environment represents an emerging source of structurally unique and novel antimicrobial agents. There are several reports on marine bacterial secondary metabolites, and many are pharmacologically significant and have enormous promise for developing effective antimicrobial drugs to combat microbial infections in drug-resistant pathogens. In this review, we attempt to summarize published articles from the last twenty-five years (1996–2020) on antimicrobial secondary metabolites from marine bacteria evolved in marine environments, such as marine sediment, water, fauna, and flora.

Culturable Microorganisms Associated with Sea Cucumbers and Microbial Natural Products

Sea cucumbers are a class of marine invertebrates and a source of food and drug. Numerous microorganisms are associated with sea cucumbers. Seventy-eight genera of bacteria belonging to 47 families in four phyla, and 29 genera of fungi belonging to 24 families in the phylum Ascomycota have been cultured from sea cucumbers. Sea-cucumber-associated microorganisms produce diverse secondary metabolites with various biological activities, including cytotoxic, antimicrobial, enzyme-inhibiting, and antiangiogenic activities. In this review, we present the current list of the 145 natural products from microorganisms associated with sea cucumbers, which include primarily polyketides, as well as alkaloids and terpenoids. These results indicate the potential of the microorganisms associated with sea cucumbers as sources of bioactive natural products.

Meroterpenoids: A Comprehensive Update Insight on Structural Diversity and Biology

Meroterpenoids are secondary metabolites formed due to mixed biosynthetic pathways which are produced in part from a terpenoid co-substrate. These mixed biosynthetically hybrid compounds are widely produced by bacteria, algae, plants, and animals. Notably amazing chemical diversity is generated among meroterpenoids via a combination of terpenoid scaffolds with polyketides, alkaloids, phenols, and amino acids. This review deals with the isolation, chemical diversity, and biological effects of 452 new meroterpenoids reported from natural sources from January 2016 to December 2020. Most of the meroterpenoids possess antimicrobial, cytotoxic, antioxidant, anti-inflammatory, antiviral, enzyme inhibitory, and immunosupressive effects.

Peculiarities of meroterpenoids and their bioproduction

Meroterpenoids are a class of terpenoid-containing hybrid natural products with impressive structural architectures and remarkable pharmacological activities. Remarkable advances in enzymology and synthetic biology have greatly contributed to the elucidation of the molecular basis for their biosynthesis. Here, we review structurally unique meroterpenoids catalyzed by novel enzymes and unusual enzymatic reactions over the period of last 5 years. We also discuss recent progress on the biomimetic synthesis of chrome meroterpenoids and synthetic biology-driven biomanufacturing of tropolone sesquiterpenoids, merochlorins, and plant-derived meroterpenoid cannabinoids. In particular, we focus on the novel enzymes involved in the biosynthesis of polyketide-terpenoids, nonribosomal peptide-terpenoids, terpenoid alkaloids, and meroterpenoid with unique structures. The biological activities of these meroterpenoids are also discussed. The information reviewed here might provide useful clues and lay the foundation for developing new meroterpenoid-derived drugs. KEY POINTS: • Meroterpenoids possess intriguing structural features and relevant biological activities. • Novel enzymes are involved in the biosynthesis of meroterpenoids with unique structures. • Biomimetic synthesis and synthetic biology enable the construction and manufacturing of complex meroterpenoids.