Panning for chemical gold: marine bacteria as a source of new therapeutics

Biosynthetic potential of the sediment microbial subcommunities of an unexplored karst ecosystem and its ecological implications

Microbial communities from various environments have been studied in the quest for new natural products with a broad range of applications in medicine and biotechnology. We employed an enrichment method and genome mining tools to examine the biosynthetic potential of microbial communities in the sediments of a coastal sinkhole within the karst ecosystem of the Yucatán Peninsula, Mexico. Our investigation led to the detection of 203 biosynthetic gene clusters (BGCs) and 55 secondary metabolites (SMs) within 35 high-quality metagenome-assembled genomes (MAGs) derived from these subcommunities. The most abundant types of BGCs were Terpene, Nonribosomal peptide-synthetase, and Type III polyketide synthase. Some of the in silico identified BGCs and SMs have been previously reported to exhibit biological activities against pathogenic bacteria and fungi. Others could play significant roles in the sinkhole ecosystem, such as iron solubilization and osmotic stress protection. Interestingly, 75% of the BGCs showed no sequence homology with bacterial BGCs previously reported in the MiBIG database. This suggests that the microbial communities in this environment could be an untapped source of genes encoding novel specialized compounds. The majority of the BGCs were identified in pathways found in the genus Virgibacillus, followed by Sporosarcina, Siminovitchia, Rhodococcus, and Halomonas. The latter, along with Paraclostridium and Lysinibacillus, had the highest number of identified BGC types. This study offers fresh insights into the potential ecological role of SMs from sediment microbial communities in an unexplored environment, underscoring their value as a source of novel natural products.

An organic extract from ascidian Ciona robusta induces cytotoxic autophagy in human malignant cell lines

The last decades have seen an increase in the isolation and characterization of anticancer compounds derived from marine organisms, especially invertebrates, and their use in clinical trials. In this regard, ascidians, which are included in the subphylum Tunicata, represent successful examples with two drugs, Aplidine© and Yondelis© that reached the market as orphan drugs against several malignancies. Here, we report that an organic extract prepared from homogenized tissues of the Mediterranean ascidian Ciona robusta inhibited cell proliferation in HT-29, HepG2, and U2OS human cells with the former being the most sensitive to the extract (EC50 = 250 μg/mL). We demonstrated that the ascidian organic extract was not cytotoxic on HT-29 cells that were induced to differentiate with sodium butyrate, suggesting a preference for the mixture for the malignant phenotype. Finally, we report that cell death induced by the organic extract was mediated by the activation of a process of cytotoxic autophagy as a result of the increased expression of the LC3-II marker and number of autophagic vacuoles, which almost doubled in the treated HT-29 cells. In summary, although the detailed chemical composition of the Ciona robusta extract is still undetermined, our data suggest the presence of bioactive compounds possessing anticancer activity.

Exploring the biosynthetic gene clusters in Brevibacterium: a comparative genomic analysis of diversity and distribution

Exploring Brevibacterium strains from various ecosystems may lead to the discovery of new antibiotic-producing strains. Brevibacterium sp. H-BE7, a strain isolated from marine sediments from Northern Patagonia, Chile, had its genome sequenced to study the biosynthetic potential to produce novel natural products within the Brevibacterium genus. The genome sequences of 98 Brevibacterium strains, including strain H-BE7, were selected for a genomic analysis. A phylogenomic cladogram was generated, which divided the Brevibacterium strains into four major clades. A total of 25 strains are potentially unique new species according to Average Nucleotide Identity (ANIb) values. These strains were isolated from various environments, emphasizing the importance of exploring diverse ecosystems to discover the full diversity of Brevibacterium. Pangenome analysis of Brevibacterium strains revealed that only 2.5% of gene clusters are included within the core genome, and most gene clusters occur either as singletons or as cloud genes present in less than ten strains. Brevibacterium strains from various phylogenomic clades exhibit diverse BGCs. Specific groups of BGCs show clade-specific distribution patterns, such as siderophore BGCs and carotenoid-related BGCs. A group of clade IV-A Brevibacterium strains possess a clade-specific Polyketide synthase (PKS) BGCs that connects with phenazine-related BGCs. Within the PKS BGC, five genes, including the biosynthetic PKS gene, participate in the mevalonate pathway and exhibit similarities with the phenazine A BGC. However, additional core biosynthetic phenazine genes were exclusively discovered in nine Brevibacterium strains, primarily isolated from cheese. Evaluating the antibacterial activity of strain H-BE7, it exhibited antimicrobial activity against Salmonella enterica and Listeria monocytogenes. Chemical dereplication identified bioactive compounds, such as 1-methoxyphenazine in the crude extracts of strain H-BE7, which could be responsible of the observed antibacterial activity. While strain H-BE7 lacks the core phenazine biosynthetic genes, it produces 1-methoxyphenazine, indicating the presence of an unknown biosynthetic pathway for this compound. This suggests the existence of alternative biosynthetic pathways or promiscuous enzymes within H-BE7's genome.

Emerging pharmaceutical therapies of Ascidian-derived natural products and derivatives

In a growing multidrug-resistant environment, the identification of potential new drug candidates with an acceptable safety profile is a substantial crux in pharmaceutical discovery. This review discusses several aspects and properties of approved marine natural products derived from ascidian sources (phylum Chordata, subphylum Tunicata) and/or their deduced analogues including their biosynthetic origin, (bio)chemical preclinical assessments and known efficacy-safety profiles, clinical status in trials, but also translational developments, opportunities and final conclusions. The review also describes the preclinical assessments of a large number of other ascidian compounds that have not been involved in clinical trials yet. Finally, the emerging research on the connectivity of the ascidian hosts and their independent or obligate symbiotic guests is discussed. The review covers the latest information on the topic of ascidian-derived marine natural products over the last two decades including 2022, with the majority of publications published in the last decade.

Cytotoxicity and apoptosis induction of the marine Conus flavidus venom in HepG2 cancer cell line

Cancer is still an area of continuous research for finding more effective and selective agents, so our study aimed to explore new anticancer medicines from Cone snails' venoms as marine natural products with promising biological activities. Venoms from seven cone snails collected from two locations on the Red Sea coast (Marsa Alam (Ma) and Hurghada (Hu)) were extracted and subjected to SDS for protein concentrations. The venoms of C. vexillum (Ma), C. vexillum (Hu), and C. flavidus were found to have the highest protein concentrations (2.66, 2.618, and 2.611 mg/mL, respectively). The venom of C. vexillum (Ma) was found to be cytotoxic against the lung cancer cell line A549 (IC50 = 4.511 ± 0.03 µg/mL). On the other hand, the venom of C. flavidus showed a strong cytotoxic effect on both liver and lung cancer cell lines (IC50 = 1.593 ± 0.05 and 7.836 ± 0.4 µg/mL, respectively) when compared to their normal cell lines. Investigating the apoptotic cell death of C. flavidus venom on HepG2 cell lines, it showed total apoptotic cell death by 22.42-fold compared to untreated control and arresting the cell cycle at G2/M phase. Furthermore, its apoptotic cell death in HepG2 cells was confirmed through the upregulation of pro-apoptotic markers and down-regulation of Bcl-2 in both gene and protein expression levels. These findings confirmed the cytotoxic activity of C. flavidus venom through apoptotic cell death in HepG2 cells. So, a detailed study highlighting its structure and molecular target for developing new anticancer agents from natural sources is required.Communicated by Ramaswamy H. Sarma.

MariClus: Your One-Stop Platform for Information on Marine Natural Products, Their Gene Clusters and Producing Organisms

BACKGROUND

The marine environment hosts the vast majority of living species and marine microbes that produce natural products with great potential in providing lead compounds for drug development. With over 70% of Earth's surface covered in water and the high interaction rate associated with liquid environments, this has resulted in many marine natural product discoveries. Our improved understanding of the biosynthesis of these molecules, encoded by gene clusters, along with increased genomic information will aid us in uncovering even more novel compounds.

RESULTS

We introduce MariClus (https://www.mariclus.com), an online user-friendly platform for mining and visualizing marine gene clusters. The first version contains information on clusters and the predicted molecules for over 500 marine-related prokaryotes. The user-friendly interface allows scientists to easily search by species, cluster type or molecule and visualize the information in table format or graphical representation.

CONCLUSIONS

This new online portal simplifies the exploration and comparison of gene clusters in marine species for scientists and assists in characterizing the bioactive molecules they produce. MariClus integrates data from public sources, like GenBank, MIBiG and PubChem, with genome mining results from antiSMASH. This allows users to access and analyze various aspects of marine natural product biosynthesis and diversity.

Antifungal and Antibacterial Activities of Isolated Marine Compounds

To combat the ineffectiveness of currently available pharmaceutical medications, caused by the emergence of increasingly resistant bacterial and fungal strains, novel antibacterial and antifungal medications are urgently needed. Novel natural compounds with antimicrobial activities can be obtained by exploring underexplored habitats such as the world's oceans. The oceans represent the largest ecosystem on earth, with a high diversity of organisms. Oceans have received some attention in the past few years, and promising compounds with antimicrobial activities were isolated from marine organisms such as bacteria, fungi, algae, sea cucumbers, sea sponges, etc. This review covers 56 antifungal and 40 antibacterial compounds from marine organisms. These compounds are categorized according to their chemical structure groups, including polyketides, alkaloids, ribosomal peptides, and terpenes, and their organismal origin. The review provides the minimum inhibitory concentration MIC values and the bacterial/fungal strains against which these chemical compounds show activity. This study shows strong potential for witnessing the development of new novel antimicrobial drugs from these natural compounds isolated and evaluated for their antimicrobial activities.

Marine Natural Products with Activities against Prostate Cancer: Recent Discoveries

Prostate cancer is the most common cancer in men, with over 52,000 new cases diagnosed every year. Diagnostics and early treatment are potentially hindered by variations in screening protocols, still largely reliant on serum levels of acid phosphatase and prostate-specific antigen, with tumour diagnosis and grading relying on histopathological examination. Current treatment interventions vary in terms of efficacy, cost and severity of side effects, and relapse can be aggressive and resistant to the current standard of care. For these reasons, the scientific community is looking for new chemotherapeutic agents. This review reports compounds and extracts derived from marine organisms as a potential source of new drugs against prostate cancer. Whilst there are several marine-derived compounds against other cancers, such as multiple myeloma, leukemia, breast and lung cancer, already available in the market, the presently collated findings show how the marine environment can be considered to hold potential as a new drug source for prostate cancer, as well. This review presents information on compounds presently in clinical trials, as well as new compounds/extracts that may enter trials in the future. We summarise information regarding mechanisms of action and active concentrations.

Marine-Inspired Drugs and Biomaterials in the Perspective of Pancreatic Cancer Therapies

Despite its low prevalence, pancreatic cancer (PC) is one of the deadliest, typically characterised as silent in early stages and with a dramatically poor prognosis when in its advanced stages, commonly associated with a high degree of metastasis. Many efforts have been made in pursuing innovative therapeutical approaches, from the search for new cytotoxic drugs and other bioactive compounds, to the development of more targeted approaches, including improved drug delivery devices. Marine biotechnology has been contributing to this quest by providing new chemical leads and materials originating from different organisms. In this review, marine biodiscovery for PC is addressed, particularly regarding marine invertebrates (namely sponges, molluscs, and bryozoans), seaweeds, fungi, and bacteria. In addition, the development of biomaterials based on marine-originating compounds, particularly chitosan, fucoidan, and alginate, for the production of advanced cancer therapies, is also discussed. The key role that drug delivery can play in new cancer treatments is highlighted, as therapeutical outcomes need to be improved to give further hope to patients.

Exploring the Antibiotic Production Potential of Heterotrophic Bacterial Communities Isolated from the Marine Sponges Crateromorpha meyeri, Pseudaxinella reticulata, Farrea similaris, and Caulophacus arcticus through Synergistic Metabolomic and Genomic Analyses

The discovery of novel secondary metabolites is actively being pursued in new ecosystems. Sponge-associated bacteria have been in the limelight in recent years on account of their ability to produce bioactive compounds. In this study, heterotrophic bacteria associated with four sponge species were isolated, taxonomically identified, and subjected to screening for the production of bioactive entities against a panel of nine microorganisms, including Gram-positive and negative bacteria, as well as yeast and fungi. Of the 105 isolated strains, 66% were represented by Proteobacteria, 16% by Bacteriodetes, 7% by Actinobacteria, and 11% by Firmicutes. Bioactivity screening revealed that 40% of the total isolated strains showed antimicrobial activity against one or more of the target microorganisms tested. Further, active extracts from selective species were narrowed down by bioassay-guided fractionation and subsequently identified by HR-ESI-MS analyses to locate the active peaks. Presumably responsible compounds for the observed bioactivities were identified as pentadecenoic acid, oleic acid, and palmitoleic acid. One isolate, Qipengyuania pacifica NZ-96T, based on 16S rRNA novelty, was subjected to comparative metabolic reconstruction analysis with its closest phylogenetic neighbors, revealing 79 unique functional roles in the novel isolate. In addition, genome mining of Qipengyuania pacifica NZ-96T revealed three biosynthetic gene clusters responsible for the biosynthesis of terpene, beta lactone, lasso peptide, and hserlactone secondary metabolites. Our results demonstrate the ability to target the sponge microbiome as a potential source of novel microbial life with biotechnological potential.

Exploring Newer Biosynthetic Gene Clusters in Marine Microbial Prospecting

Marine microbes genetically evolved to survive varying salinity, temperature, pH, and other stress factors by producing different bioactive metabolites. These microbial secondary metabolites (SMs) are novel, have high potential, and could be used as lead molecule. Genome sequencing of microbes revealed that they have the capability to produce numerous novel bioactive metabolites than observed under standard in vitro culture conditions. Microbial genome has specific regions responsible for SM assembly, termed biosynthetic gene clusters (BGCs), possessing all the necessary genes to encode different enzymes required to generate SM. In order to augment the microbial chemo diversity and to activate these gene clusters, various tools and techniques are developed. Metagenomics with functional gene expression studies aids in classifying novel peptides and enzymes and also in understanding the biosynthetic pathways. Genome shuffling is a high-throughput screening approach to improve the development of SMs by incorporating genomic recombination. Transcriptionally silent or lower level BGCs can be triggered by artificially knocking promoter of target BGC. Additionally, bioinformatic tools like antiSMASH, ClustScan, NAPDOS, and ClusterFinder are effective in identifying BGCs of existing class for annotation in genomes. This review summarizes the significance of BGCs and the different approaches for detecting and elucidating BGCs from marine microbes.

The Immune System of Marine Organisms as Source for Drugs against Infectious Diseases

The high proliferation of microorganisms in aquatic environments has allowed their coevolution for billions of years with other living beings that also inhabit these niches. Among the different existing types of interaction, the eternal competition for supremacy between the susceptible species and their pathogens has selected, as part of the effector division of the immune system of the former ones, a vast and varied arsenal of efficient antimicrobial molecules, which is highly amplified by the broad biodiversity radiated, above any others, at the marine habitats. At present, the great recent scientific and technological advances already allow the massive discovery and exploitation of these defense compounds for therapeutic purposes against infectious diseases of our interest. Among them, antimicrobial peptides and antimicrobial metabolites stand out because of the wide dimensions of their structural diversities, mechanisms of action, and target pathogen ranges. This revision work contextualizes the research in this field and serves as a presentation and scope identification of the Special Issue from Marine Drugs journal “The Immune System of Marine Organisms as Source for Drugs against Infectious Diseases”.

Identification of a Novel Metallo-β-Lactamase, VAM-1, in a Foodborne Vibrio alginolyticus Isolate from China

A multidrug-resistant Vibrio alginolyticus isolate recovered from a shrimp sample with reduced carbapenem susceptibility produced a novel metallo-β-lactamase (MBL), VAM-1. That carbapenemase shared 67% to 70% amino acid identity with several VMB family subclass B1 MBLs, which were recently reported among some marine bacteria including Vibrio, Glaciecola, and Thalassomonas. The blaVAM-1 gene was located in a novel conjugative plasmid, namely, pC1579, and multiple copies of blaVAM-1 via an unusual mechanism of gene amplification were detected in pC1579. These findings underline the emergence of marine organisms acting as natural reservoirs for MBL genes and the importance of continuous bacterial antibiotic resistance surveillance.

Marine-derived pipeline anticancer natural products: a review of their pharmacotherapeutic potential and molecular mechanisms

Background

Cancer is a complex and most widespread disease and its prevalence is increasing worldwide, more in countries that are witnessing urbanization and rapid industrialization changes. Although tremendous progress has been made, the interest in targeting cancer has grown rapidly every year. This review underscores the importance of preventive and therapeutic strategies.

Main text

Natural products (NPs) from various sources including plants have always played a crucial role in cancer treatment. In this growing list, numerous unique secondary metabolites from marine sources have added and gaining attention and became potential players in drug discovery and development for various biomedical applications. Many NPs found in nature that normally contain both pharmacological and biological activity employed in pharmaceutical industry predominantly in anticancer pharmaceuticals because of their enormous range of structure entities with unique functional groups that attract and inspire for the creation of several new drug leads through synthetic chemistry. Although terrestrial medicinal plants have been the focus for the development of NPs, however, in the last three decades, marine origins that include invertebrates, plants, algae, and bacteria have unearthed numerous novel pharmaceutical compounds, generally referred as marine NPs and are evolving continuously as discipline in the molecular targeted drug discovery with the inclusion of advanced screening tools which revolutionized and became the component of antitumor modern research.

Conclusions

This comprehensive review summarizes some important and interesting pipeline marine NPs such as Salinosporamide A, Dolastatin derivatives, Aplidine/plitidepsin (Aplidin®) and Coibamide A, their anticancer properties and describes their mechanisms of action (MoA) with their efficacy and clinical potential as they have attracted interest for potential use in the treatment of various types of cancers.

Bioactive Secondary Metabolites from Marine Streptomyces griseorubens f8: Isolation, Identification and Biological Activity Assay

Marine actinomycetes are a potential source of a wide variety of bioactive natural products. Herein, four cyclic dipeptides, namely, cyclo(L-Val-L-Pro) (compound 1), cyclo(L-Pro-L-Leu) (compound 2), cyclo(L-Pro-L-Tyr) (compound 3) and cyclo(L-Pro-L-Phe) (compound 5), and an N-acetyltyramine (compound 4) were first isolated and identified as products of the marine Streptomyces griseorubens f8. Compounds 3 and 5 exhibit antibacterial activity against Staphylococcus aureus, Klebsiella aerogenes and Proteus vulgaris. The minimum inhibitory concentrations (MICs) against Staphylococcus aureus, Klebsiella aerogenes and Proteus vulgaris are 160 µg/mL, 100 µg/mL, 120 µg/mL for the compound 3 and 180 µg/mL, 130 µg/mL 150 µg/mL for the compound 5, respectively. In addition, compounds 1, 2, 3 and 5 was first found to have the ability to inhibit the invasion and migration of A549 cells (lung cancer cells), which exhibited the potentiality for these compounds to be used as novel anticancer drugs. This study provides a novel production strain for compounds 1, 2, 3 and 5, and four potential promising anticancer agents.

Promising Activities of Marine Natural Products against Hematopoietic Malignancies

According to the WHO classification of tumors, more than 150 typologies of hematopoietic and lymphoid tumors exist, and most of them remain incurable diseases that require innovative approaches to improve therapeutic outcome and avoid side effects. Marine organisms represent a reservoir of novel bioactive metabolites, but they are still less studied compared to their terrestrial counterparts. This review is focused on marine natural products with anticancer activity against hematological tumors, highlighting recent advances and possible perspectives. Until now, there are five commercially available marine-derived compounds for the treatment of various hematopoietic cancers (e.g., leukemia and lymphoma), two molecules in clinical trials, and series of compounds and/or extracts from marine micro- and macroorganisms which have shown promising properties. In addition, the mechanisms of action of several active compounds and extracts are still unknown and require further study. The continuous upgrading of omics technologies has also allowed identifying enzymes with possible bioactivity (e.g., l-asparaginase is currently used for the treatment of leukemia) or the enzymes involved in the synthesis of bioactive secondary metabolites which can be the target of heterologous expression and genetic engineering.

Antiangiogenic molecules from marine actinomycetes and the importance of using zebrafish model in cancer research

Blood vessel sprouting from pre-existing vessels or angiogenesis plays a significant role in tumour progression. Development of novel biomolecules from marine natural sources has a promising role in drug discovery specifically in the area of antiangiogenic chemotherapeutics. Symbiotic actinomycetes from marine origin proved to be potent and valuable sources of antiangiogenic compounds. Zebrafish represent a well-established model for small molecular screening and employed to study tumour angiogenesis over the last decade. Use of zebrafish has increased in the laboratory due to its various advantages like rapid embryo development, optically transparent embryos, large clutch size of embryos and most importantly high genetic conservation comparable to humans. Zebrafish also shares similar physiopathology of tumour angiogenesis with humans and with these advantages, zebrafish has become a popular model in the past decade to study on angiogenesis related disorders like diabetic retinopathy and cancer. This review focuses on the importance of antiangiogenic compounds from marine actinomycetes and utility of zebrafish in cancer angiogenesis research.

The Marine Sponge Petrosia ficiformis Harbors Different Cyanobacteria Strains with Potential Biotechnological Application

Marine cyanobacteria are a source of bioactive natural compounds, with a wide range of biotechnological applications. However, information on sponge-associated cyanobacteria are relatively scarce to date. In this paper, we carried out the morphological and molecular characterization of eight cyanobacterial strains, previously isolated from the Mediterranean sponge Petrosia ficiformis, and evaluated their biological activities on epithelial- and neuron-like cultured cells of human and murine origin. The new analysis allowed maintaining the assignment of three strains (Cyanobium sp., Leptolyngbya ectocarpi, and Synechococcus sp.), while two strains previously identified as Synechococcus sp. and Leptolyngbya sp. were assigned to Pseudanabaena spp. One strain, i.e., ITAC104, and the ITAC101 strain corresponding to Halomicronema metazoicum, shared extremely high sequence identity, practically representing two clones of the same species. Finally, for only one strain, i.e., ITAC105, assignment to a specific genus was not possible. Concerning bioactivity analyses, incubation of cyanobacterial aqueous cell supernatants induced variable responses in cultured cells, depending on cell type, with some of them showing toxic activity on human epithelial-like cells and no toxic effects on human and rat neuron-like cells. Future investigations will allow to better define the bioactive properties of these cyanobacteria strains and to understand if they can be useful for (a) therapeutic purpose(s).

Deciphering Biosynthetic Enzymes Leading to 4-Chloro-6-Methyl-5,7-Dihydroxyphenylglycine, a Non-Proteinogenic Amino Acid in Totopotensamides

Totopotensamide A (TPM A, 1) is a polyketide-peptide glycoside featuring a nonproteinogenic amino acid 4-chloro-6-methyl-5,7-dihydroxyphenylglycine (ClMeDPG). The biosynthetic gene cluster (BGC) of totopotensamides (tot) was previously activated by manipulating transcription regulators in marine-derived Streptomyces pactum SCSIO 02999. Herein, we report the heterologous expression of the tot BGC in Streptomyces lividans TK64, and the production improvement of TPM A via in-frame deletion of two negative regulators totR5 and totR3. The formation of ClMeDPG was proposed to require six enzymes, including four enzymes TotC1C2C3C4 for 3,5-dihydroxyphenylglycine (DPG) biosynthesis and two modifying enzymes TotH (halogenase) and TotM (methyltransferase). Heterologous expression of the four-gene cassette totC1C2C3C4 led to production of 3,5-dihydroxyphenylglyoxylate (DPGX). The aminotransferase TotC4 was biochemically characterized to convert DPGX to S-DPG. Inactivation of totH led to a mutant accumulated a deschloro derivative TPM H1, and the ΔtotHi/ΔtotMi double mutant afforded two deschloro-desmethyl products TPMs HM1 and HM2. A hydrolysis experiment demonstrated that the DPG moiety in TPM HM2 was S-DPG, consistent with that of the TotC4 enzymatic product. These results confirmed that TotH and TotM were responsible for ClMeDPG biosynthesis. Bioinformatics analysis indicated that both TotH and TotM might act on thiolation domain-tethered substrates. This study provided evidence for deciphering enzymes leading to ClMeDPG in TPM A, and unambiguously determined its absolute configuration as S.

A metal-, oxidant-, and fluorous solvent-free synthesis of α-indolylketones enabled by an umpolung strategy

We have developed the first transition metal-, oxidant-, and fluorous solvent-free α-indolization of ketones using ammonium salts and enamines.

Bioactive Streptoglutarimides A-J from the Marine-Derived Streptomyces sp. ZZ741

The new streptoglutarimides A-J (1-10) and the known streptovitacin A (11) were isolated from a marine-derived actinomycete, Streptomyces sp. ZZ741. Structures of the isolated compounds were elucidated based on their HRESIMS data, extensive NMR spectroscopic analyses, ECD calculations, Mosher's method, and a single-crystal X-ray diffraction experiment. Streptoglutarimide H (8) and streptovitacin A (11) showed potent antiproliferative activity against human glioma U87MG and U251 cells with IC₅₀ values of 1.5-3.8 μM for 8 and 0.05-0.22 μM for 11. All isolated compounds exhibited antimicrobial activity with MIC values of 9-11 μg/mL against methicillin-resistant Staphylococcus aureus, 8-12 μg/mL against Escherichia coli, and 8-20 μg/mL against Candida albicans.

Computational modeling of culture media for enhanced production of fibrinolytic enzyme from marine bacterium Fictibacillus sp. strain SKA27 and in vitro evaluation of fibrinolytic activity

The present study reports the optimized production and purification of an extremely active fibrinolytic enzyme from newly isolated marine bacterium Fictibacillus sp. strain SKA27, with a specific activity of 125,107.85 U/mg and an apparent molecular weight of 28 kDa on SDS-PAGE. Wheat bran extract used for submerged production proved to be highly beneficial and enhanced fibrinolytic enzyme production when combined with yeast extract and CaCl₂. Optimization of culture media by response surface methodology (RSM) resulted in high root mean square error (RMSE), which led to the training of a back propagation multilayer artificial neural network (ANN) with 3-5-1 topology for better prediction quality. The prediction and optimization capabilities of regression and ANN were critically examined and ANN displayed higher proficiency with R ² of 0.99 and RMSE of 2.0 compared to 0.98 R ² and 48.9 RMSE of the regression model. An adept ANN linked genetic algorithm (GA) optimized the medium components to achieve 1.8-fold higher enzyme production (4175.41 U/mL). Further, a new and improved in vitro qualitative analysis displayed high specificity of purified enzyme to fibrin.

Streptomyces monashensis sp. nov., a novel mangrove soil actinobacterium from East Malaysia with antioxidative potential

A new Streptomyces species discovered from Sarawak mangrove soil is described, with the proposed name - Streptomyces monashensis sp. nov. (strain MUSC 1JT). Taxonomy status of MUSC 1JT was determined via polyphasic approach. Phylogenetic and chemotaxonomic properties of strain MUSC 1JT were in accordance with those known for genus Streptomyces. Based on phylogenetic analyses, the strains closely related to MUSC 1JT were Streptomyces corchorusii DSM 40340T (98.7%), Streptomyces olivaceoviridis NBRC 13066T (98.7%), Streptomyces canarius NBRC 13431T (98.6%) and Streptomyces coacervatus AS-0823T (98.4%). Outcomes of DNA-DNA relatedness between strain MUSC 1JT and its closely related type strains covered from 19.7 ± 2.8% to 49.1 ± 4.3%. Strain MUSC 1JT has genome size of 10,254,857 bp with DNA G + C content of 71 mol%. MUSC 1JT extract exhibited strong antioxidative activity up to 83.80 ± 4.80% in the SOD assay, with significant cytotoxic effect against colon cancer cell lines HCT-116 and SW480. Streptomyces monashensis MUSC 1JT (=DSM 103626T = MCCC 1K03221T) could potentially be a producer of novel bioactive metabolites; hence discovery of this new species may be highly significant to the biopharmaceutical industry as it could lead to development of new and useful chemo-preventive drugs.

New Approaches to Detect Biosynthetic Gene Clusters in the Environment

Microorganisms in the environment can produce a diverse range of secondary metabolites (SM), which are also known as natural products. Bioactive SMs have been crucial in the development of antibiotics and can also act as useful compounds in the biotechnology industry. These natural products are encoded by an extensive range of biosynthetic gene clusters (BGCs). The developments in omics technologies and bioinformatic tools are contributing to a paradigm shift from traditional culturing and screening methods to bioinformatic tools and genomics to uncover BGCs that were previously unknown or transcriptionally silent. Natural product discovery using bioinformatics and omics workflow in the environment has demonstrated an extensive distribution of BGCs in various environments, such as soil, aquatic ecosystems and host microbiome environments. Computational tools provide a feasible and culture-independent route to find new secondary metabolites where traditional approaches cannot. This review will highlight some of the advances in the approaches, primarily bioinformatic, in identifying new BGCs, especially in environments where microorganisms are rarely cultured. This has allowed us to tap into the huge potential of microbial dark matter.

Jellyfish-Associated Microbiome in the Marine Environment: Exploring Its Biotechnological Potential

Despite accumulating evidence of the importance of the jellyfish-associated microbiome to jellyfish, its potential relevance to blue biotechnology has only recently been recognized. In this review, we emphasize the biotechnological potential of host⁻microorganism systems and focus on gelatinous zooplankton as a host for the microbiome with biotechnological potential. The basic characteristics of jellyfish-associated microbial communities, the mechanisms underlying the jellyfish-microbe relationship, and the role/function of the jellyfish-associated microbiome and its biotechnological potential are reviewed. It appears that the jellyfish-associated microbiome is discrete from the microbial community in the ambient seawater, exhibiting a certain degree of specialization with some preferences for specific jellyfish taxa and for specific jellyfish populations, life stages, and body parts. In addition, different sampling approaches and methodologies to study the phylogenetic diversity of the jellyfish-associated microbiome are described and discussed. Finally, some general conclusions are drawn from the existing literature and future research directions are highlighted on the jellyfish-associated microbiome.

Medicinal Purposes: Bioactive Metabolites from Marine-derived Organisms

The environment of marine occupies about 95% biosphere of the world and it can be a critical source of bioactive compounds for humans to be explored. Special environment such as high salt, high pressure, low temperature, low nutrition and no light, etc. has made the production of bioactive substances different from terrestrial organisms. Natural ingredients secreted by marine-derived bacteria, fungi, actinomycetes, Cyanobacteria and other organisms have been separated as active pharmacophore. A number of evidences have demonstrated that bioactive ingredients isolated from marine organisms can be other means to discover novel medicines, since enormous natural compounds from marine environment were specified to be anticancer, antibacterial, antifungal, antitumor, cytotoxic, cytostatic, anti-inflammatory, antiviral agents, etc. Although considerable progress is being made within the field of chemical synthesis and engineering biosynthesis of bioactive compounds, marine environment still remains the richest and the most diverse sources for new drugs. This paper reviewed the natural compounds discovered recently from metabolites of marine organisms, which possess distinct chemical structures that may form the basis for the synthesis of new drugs to combat resistant pathogens of human life. With developing sciences and technologies, marine-derived bioactive compounds are still being found, showing the hope of solving the problems of human survival and sustainable development of resources and environment.

Hexaricins, Pradimicin-like Polyketides from a Marine Sediment-Derived Streptosporangium sp. and Their Antioxidant Effects

Seven pradimicin-like polyketides were isolated from the dichloromethane extract of the marine sediment-derived Streptosporangium sp. CGMCC 4.7309, including five new hexaricins, D-H (1-5), and known hexaricins A (6) and C (7). Their structures were determined by HRESIMS, 1D and 2D NMR, and other spectroscopic analyses. The absolute configurations of compounds 1-5 were determined on the basis of circular dichroism and specific rotation data. All isolated compounds 1-7 were tested for their antioxidant capacities by DPPH^• scavenging, ^•OH scavenging, and ^•O₂̅ scavenging assays. Compounds 3 and 4 displayed stronger antioxidant activities than the positive control ( tert-butylhydroquinone). The relationship between structure and antioxidant activity is discussed. These compounds could be effective natural antioxidants with considerable pharmaceutical value.

Reproductive System Symbiotic Bacteria Are Conserved between Two Distinct Populations of Euprymna scolopes from Oahu, Hawaii

In this study, we examined the reproductive ANG symbiosis found in two genetically isolated populations of the Hawaiian bobtail squid, Euprymna scolopes. The stability of the community reported here provides support for the hypothesis that this symbiosis is under strong selective pressure, while the observed differences suggest that some level of local adaptation may have occurred. These two host populations are frequently used interchangeably as source populations for research. Euprymna scolopes is an important model organism and offers the opportunity to examine the interplay between a binary and a consortial symbiosis in a single model host. Understanding the inherent natural variability of this association will aid in our understanding of the conservation, function, transmission, and development of the ANG symbiosis.

Female Hawaiian bobtail squid, Euprymna scolopes, harbor a symbiotic bacterial community in a reproductive organ, the accessory nidamental gland (ANG). This community is known to be stable over several generations of wild-caught bobtail squid but has, to date, been examined for only one population in Maunalua Bay, Oahu, HI. This study assessed the ANG and corresponding egg jelly coat (JC) bacterial communities for another genetically isolated host population from Kaneohe Bay, Oahu, HI, using 16S amplicon sequencing. The bacterial communities from the ANGs and JCs of the two populations were found to be similar in richness, evenness, phylogenetic diversity, and overall community composition. However, the Kaneohe Bay samples formed their own subset within the Maunalua Bay ANG/JC community. An Alteromonadaceae genus, BD2-13, was significantly higher in relative abundance in the Kaneohe Bay population, and several Alphaproteobacteria taxa also shifted in relative abundance between the two groups. This variation could be due to local adaptation to differing environmental challenges, to localized variability, or to functional redundancy among the ANG taxa. The overall stability of the community between the populations further supports a crucial functional role that has been hypothesized for this symbiosis.

IMPORTANCE In this study, we examined the reproductive ANG symbiosis found in two genetically isolated populations of the Hawaiian bobtail squid, Euprymna scolopes. The stability of the community reported here provides support for the hypothesis that this symbiosis is under strong selective pressure, while the observed differences suggest that some level of local adaptation may have occurred. These two host populations are frequently used interchangeably as source populations for research. Euprymna scolopes is an important model organism and offers the opportunity to examine the interplay between a binary and a consortial symbiosis in a single model host. Understanding the inherent natural variability of this association will aid in our understanding of the conservation, function, transmission, and development of the ANG symbiosis.

Growth Promotion and Disease Suppression Ability of a Streptomyces sp. CB-75 from Banana Rhizosphere Soil

An actinomycete strain, CB-75, was isolated from the soil of a diseased banana plantation in Hainan, China. Based on phenotypic and molecular characteristics, and 99.93% sequence similarity with Streptomyces spectabilis NBRC 13424 (AB184393), the strain was identified as Streptomyces sp. This strain exhibited broad-spectrum antifungal activity against 11 plant pathogenic fungi. Type I polyketide synthase (PKS-I) and non-ribosomal peptide synthetase (NRPS) were detected, which were indicative of the antifungal compounds that Streptomyces sp. CB-75 could produce. An ethyl acetate extract from the strain exhibited the lowest minimum inhibitory concentration (MIC) against Colletotrichum musae (ATCC 96167) (0.78 μg/ml) and yielded the highest antifungal activity against Colletotrichum gloeosporioides (ATCC 16330) (50.0 μg/ml). Also, spore germination was significantly inhibited by the crude extract. After treatment with the crude extract of Streptomyces sp. CB-75 at the concentration 2 × MIC, the pathogenic fungi showed deformation, shrinkage, collapse, and tortuosity when observed by scanning electron microscopy (SEM). By gas chromatography-mass spectrometry (GC-MS) of the crude extract, 18 chemical constituents were identified; (Z)-13-docosenamide was the major constituent. Pot experiments showed that the incidence of banana seedlings was reduced after using Streptomyces sp. CB-75 treatment. The disease index was 10.23, and the prevention and control effect was 83.12%. Furthermore, Streptomyces sp. CB-75 had a growth-promoting effect on banana plants. The chlorophyll content showed 88.24% improvement, the leaf area, root length, root diameter, plant height, and stem showed 88.24, 90.49, 136.17, 61.78, and 50.98% improvement, respectively, and the shoot fresh weight, root fresh weight, shoot dry weight, and root dry weight showed 82.38, 72.01, 195.33, and 113.33% improvement, respectively, compared with treatment of fermentation broth without Streptomyces sp. CB-75. Thus, Streptomyces sp. CB-75 is an important microbial resource as a biological control against plant pathogenic fungi and for promoting banana growth.

An Overview on Marine Sponge-Symbiotic Bacteria as Unexhausted Sources for Natural Product Discovery

Microbial symbiotic communities of marine macro-organisms carry functional metabolic profiles different to the ones found terrestrially and within surrounding marine environments. These symbiotic bacteria have increasingly been a focus of microbiologists working in marine environments due to a wide array of reported bioactive compounds of therapeutic importance resulting in various patent registrations. Revelations of symbiont-directed host specific functions and the true nature of host-symbiont interactions, combined with metagenomic advances detecting functional gene clusters, will inevitably open new avenues for identification and discovery of novel bioactive compounds of biotechnological value from marine resources. This review article provides an overview on bioactive marine symbiotic organisms with specific emphasis placed on the sponge-associated ones and invites the international scientific community to contribute towards establishment of in-depth information of the environmental parameters defining selection and acquisition of true symbionts by the host organisms.

Biodiversity of Actinobacteria from the South Pacific and the Assessment of Streptomyces Chemical Diversity with Metabolic Profiling

Recently, bioprospecting in underexplored habitats has gained enhanced focus, since new taxa of marine actinobacteria can be found, and thus possible new metabolites. Actinobacteria are in the foreground due to their versatile production of secondary metabolites that present various biological activities, such as antibacterials, antitumorals and antifungals. Chilean marine ecosystems remain largely unexplored and may represent an important source for the discovery of bioactive compounds. Various culture conditions to enrich the growth of this phylum were used and 232 bacterial strains were isolated. Comparative analysis of the 16S rRNA gene sequences led to identifying genetic affiliations of 32 genera, belonging to 20 families. This study shows a remarkable culturable diversity of actinobacteria, associated to marine environments along Chile. Furthermore, 30 streptomycete strains were studied to establish their antibacterial activities against five model strains, Staphylococcus aureus, Listeria monocytogenes, Salmonella enterica, Escherichia coli and Pseudomonas aeruginosa, demonstrating abilities to inhibit bacterial growth of Gram-positive bacteria. To gain insight into their metabolic profiles, crude extracts were submitted to liquid chromatography-high resolution mass spectrometry (LC-HRMS) analysis to assess the selection of streptomycete strains with potentials of producing novel bioactive metabolites. The combined approach allowed for the identification of three streptomycete strains to pursue further investigations. Our Chilean marine actinobacterial culture collection represents an important resource for the bioprospection of novel marine actinomycetes and its metabolites, evidencing their potential as producers of natural bioproducts.

Evaluating Nitrogen-Containing Biosynthetic Products Produced by Saltwater Culturing of Several California Littoral Zone Gram-Negative Bacteria

The biosynthetic potential of marine-sediment-derived Gram-negative bacteria is poorly understood. Sampling of California near-shore marine environments afforded isolation of numerous Gram-negative bacteria in the Proteobacteria and Bacteriodetes phyla, which were grown in the laboratory to provide extracts whose metabolites were identified by comparative analyses of LC-mass spectrometry and MSn data. Overall, we developed an assemblage of seven bacterial strains grown in five different media types designed to coax out unique secondary metabolite production as a function of varying culture conditions. The changes in metabolite production patterns were tracked using the GNPS MS2 fragmentation pattern analysis tool. A variety of nitrogen-rich metabolites were visualized from the different strains grown in different media, and strikingly, all of the strains examined produced the same new, proton-atom-deficient compound, 1-methyl-4-methylthio-β-carboline (1), C13H12N2S. Scale-up liquid culture of Achromobacter spanius (order: Burkholderiales; class: Betaproteobacteria) provided material for the final structure elucidation. The methods successfully combined in this work should stimulate future studies of molecules from marine-derived Gram-negative bacteria.

An Updated Review on Marine Anticancer Compounds: The Use of Virtual Screening for the Discovery of Small-Molecule Cancer Drugs

Marine secondary metabolites are a promising source of unexploited drugs that have a wide structural diversity and have shown a variety of biological activities. These compounds are produced in response to the harsh and competitive conditions that occur in the marine environment. Invertebrates are considered to be among the groups with the richest biodiversity. To date, a significant number of marine natural products (MNPs) have been established as antineoplastic drugs. This review gives an overview of MNPs, both in research or clinical stages, from diverse organisms that were reported as being active or potentially active in cancer treatment in the past seventeen years (from January 2000 until April 2017) and describes their putative mechanisms of action. The structural diversity of MNPs is also highlighted and compared with the small-molecule anticancer drugs in clinical use. In addition, this review examines the use of virtual screening for MNP-based drug discovery and reveals that classical approaches for the selection of drug candidates based on ADMET (absorption, distribution, metabolism, excretion, and toxicity) filtering may miss potential anticancer lead compounds. Finally, we introduce a novel and publically accessible chemical library of MNPs for virtual screening purposes.

Streptomyces colonosanans sp. nov., A Novel Actinobacterium Isolated from Malaysia Mangrove Soil Exhibiting Antioxidative Activity and Cytotoxic Potential against Human Colon Cancer Cell Lines

Streptomyces colonosanans MUSC 93J^T, a novel strain isolated from mangrove forest soil located at Sarawak, Malaysia. The bacterium was noted to be Gram-positive and to form light yellow aerial and vivid yellow substrate mycelium on ISP 2 agar. The polyphasic approach was used to determine the taxonomy of strain MUSC 93J^T and the strain showed a range of phylogenetic and chemotaxonomic properties consistent with those of the members of the genus Streptomyces. Phylogenetic and 16S rRNA gene sequence analysis indicated that closely related strains include Streptomyces malachitofuscus NBRC 13059^T (99.2% sequence similarity), Streptomyces misionensis NBRC 13063^T (99.1%), and Streptomyces phaeoluteichromatogenes NRRL 5799^T (99.1%). The DNA–DNA relatedness values between MUSC 93J^T and closely related type strains ranged from 14.4 ± 0.1 to 46.2 ± 0.4%. The comparison of BOX-PCR fingerprints indicated MUSC 93J^T exhibits a unique DNA profile. The genome of MUSC 93J^T consists of 7,015,076 bp. The DNA G + C content was determined to be 69.90 mol%. The extract of strain MUSC 93J^T was demonstrated to exhibit potent antioxidant activity via ABTS, metal chelating, and SOD assays. This extract also exhibited anticancer activity against human colon cancer cell lines without significant cytotoxic effect against human normal colon cells. Furthermore, the chemical analysis of the extract further emphasizes the strain is producing chemo-preventive related metabolites. Based on this polyphasic study of MUSC 93J^T, it is concluded that this strain represents a novel species, for which the name Streptomyces colonosanans sp. nov. is proposed. The type strain is MUSC 93J^T (= DSM 102042^T = MCCC 1K02298^T).

Comparative Genomics of DNA Recombination and Repair in Cyanobacteria: Biotechnological Implications

Cyanobacteria are fascinating photosynthetic prokaryotes that are regarded as the ancestors of the plant chloroplast; the purveyors of oxygen and biomass for the food chain; and promising cell factories for an environmentally friendly production of chemicals. In colonizing most waters and soils of our planet, cyanobacteria are inevitably challenged by environmental stresses that generate DNA damages. Furthermore, many strains engineered for biotechnological purposes can use DNA recombination to stop synthesizing the biotechnological product. Hence, it is important to study DNA recombination and repair in cyanobacteria for both basic and applied research. This review reports what is known in a few widely studied model cyanobacteria and what can be inferred by mining the sequenced genomes of morphologically and physiologically diverse strains. We show that cyanobacteria possess many E. coli-like DNA recombination and repair genes, and possibly other genes not yet identified. E. coli-homolog genes are unevenly distributed in cyanobacteria, in agreement with their wide genome diversity. Many genes are extremely well conserved in cyanobacteria (mutMS, radA, recA, recFO, recG, recN, ruvABC, ssb, and uvrABCD), even in small genomes, suggesting that they encode the core DNA repair process. In addition to these core genes, the marine Prochlorococcus and Synechococcus strains harbor recBCD (DNA recombination), umuCD (mutational DNA replication), as well as the key SOS genes lexA (regulation of the SOS system) and sulA (postponing of cell division until completion of DNA reparation). Hence, these strains could possess an E. coli-type SOS system. In contrast, several cyanobacteria endowed with larger genomes lack typical SOS genes. For examples, the two studied Gloeobacter strains lack alkB, lexA, and sulA; and Synechococcus PCC7942 has neither lexA nor recCD. Furthermore, the Synechocystis PCC6803 lexA product does not regulate DNA repair genes. Collectively, these findings indicate that not all cyanobacteria have an E. coli-type SOS system. Also interestingly, several cyanobacteria possess multiple copies of E. coli-like DNA repair genes, such as Acaryochloris marina MBIC11017 (2 alkB, 3 ogt, 7 recA, 3 recD, 2 ssb, 3 umuC, 4 umuD, and 8 xerC), Cyanothece ATCC51142 (2 lexA and 4 ruvC), and Nostoc PCC7120 (2 ssb and 3 xerC).

Differential genotoxicity and cytotoxicity of phomoxanthone A isolated from the fungus Phomopsis longicolla in HL60 cells and peripheral blood lymphocytes

Phomoxanthone A (PhoA) is a compound isolated from the endophytic fungus Phomopsis longicolla, associated with marine algae Bostrychia radicans. Although this metabolite was previously described regarding its high biological potential, there are no reports concerning the effects of this compound on DNA integrity. This study aimed to evaluate, in lymphocytes and promyelocytic leukemia HL60 cells, the cytotoxicity of this compound through MTT and neutral red (NR) assays, as well as its genotoxicity and mutagenicity by alkaline comet assay and cytokinesis-block micronucleus cytome assay (CBMN-Cyt), respectively. Cells were treated with PhoA concentrations ranging from 0.01 to 100.0μg/mL, and the results show that this molecule did not exhibit cytotoxicity, genotoxicity or mutagenicity in lymphocytes at any tested concentration. Furthermore, PhoA was highly cytotoxic, genotoxic and mutagenic to HL60 cells, establishing a differential response of this natural product in normal and cancer cells. PhoA was highly selective towards HL60 compared to lymphocytes, causing no damage in the latter cell line, suggesting that this compound could be a promising compound in antitumoral drug development.

Streptomyces antioxidans sp. nov., a Novel Mangrove Soil Actinobacterium with Antioxidative and Neuroprotective Potentials

A novel strain, Streptomyces antioxidans MUSC 164^T was recovered from mangrove forest soil located at Tanjung Lumpur, Malaysia. The Gram-positive bacterium forms yellowish-white aerial and brilliant greenish yellow substrate mycelium on ISP 2 agar. A polyphasic approach was used to determine the taxonomy status of strain MUSC 164^T. The strain showed a spectrum of phylogenetic and chemotaxonomic properties consistent with those of the members of the genus Streptomyces. The cell wall peptidoglycan was determined to contain LL-diaminopimelic acid. The predominant menaquinones were identified as MK-9(H₆) and MK-9(H₈), while the identified polar lipids consisted of aminolipid, diphosphatidylglycerol, glycolipid, hydroxyphosphatidylethanolamine, phospholipid, phosphatidylinositol, phosphatidylethanolamine, phosphatidylglycerol and lipid. The cell wall sugars consist of galactose, glucose and ribose. The predominant cellular fatty acids (>10.0%) were identified as iso-C_15:0 (34.8%) and anteiso-C_15:0(14.0%). Phylogenetic analysis identified that closely related strains for MUSC 164^T as Streptomyces javensis NBRC 100777^T (99.6% sequence similarity), Streptomyces yogyakartensis NBRC 100779^T (99.6%) and Streptomyces violaceusniger NBRC 13459^T (99.6%). The DNA–DNA relatedness values between MUSC 164^T and closely related type strains ranged from 23.8 ± 0.3% to 53.1 ± 4.3%. BOX-PCR fingerprints comparison showed that MUSC 164^T exhibits a unique DNA profile, with DNA G + C content determined to be 71.6 mol%. Based on the polyphasic study of MUSC 164^T, it is concluded that this strain represents a novel species, for which the name Streptomyces antioxidans sp. nov. is proposed. The type strain is MUSC 164^T (=DSM 101523^T = MCCC 1K01590^T). The extract of MUSC 164^T showed potent antioxidative and neuroprotective activities against hydrogen peroxide. The chemical analysis of the extract revealed that the strain produces pyrazines and phenolic-related compounds that could explain for the observed bioactivities.

Antioxidant activity of 1-hydroxy-1-norresistomycin derived from Streptomyces variabilis KP149559 and evaluation of its toxicity against zebra fish Danio rerio

Extraction of bioactive compounds from marine actinomycetes and its antimicrobial activity.

Antitumor Effects and Related Mechanisms of Penicitrinine A, a Novel Alkaloid with a Unique Spiro Skeleton from the Marine Fungus Penicillium citrinum

Penicitrinine A, a novel alkaloid with a unique spiro skeleton, was isolated from a marine-derived fungus Penicillium citrinum. In this study, the isolation, structure and biosynthetic pathway elucidation of the new compound were described. This new compound showed anti-proliferative activity on multiple tumor types. Among them, the human malignant melanoma cell A-375 was confirmed to be the most sensitive. Morphologic evaluation, apoptosis rate analysis, Western blot and real-time quantitative PCR (RT-qPCR) results showed penicitrinine A could significantly induce A-375 cell apoptosis by decreasing the expression of Bcl-2 and increasing the expression of Bax. Moreover, we investigated the anti-metastatic effects of penicitrinine A in A-375 cells by wound healing assay, trans-well assay, Western blot and RT-qPCR. The results showed penicitrinine A significantly suppressed metastatic activity of A-375 cells by regulating the expression of MMP-9 and its specific inhibitor TIMP-1. These findings suggested that penicitrinine A might serve as a potential antitumor agent, which could inhibit the proliferation and metastasis of tumor cells.

The antimicrobial activity of heterotrophic bacteria isolated from the marine sponge Erylus deficiens (Astrophorida, Geodiidae)

Interest in the study of marine sponges and their associated microbiome has increased both for ecological reasons and for their great biotechnological potential. In this work, heterotrophic bacteria associated with three specimens of the marine sponge Erylus deficiens, were isolated in pure culture, phylogenetically identified and screened for antimicrobial activity. The isolation of bacteria after an enrichment treatment in heterotrophic medium revealed diversity in bacterial composition with only Pseudoalteromonas being shared by two specimens. Of the 83 selected isolates, 58% belong to Proteobacteria, 23% to Actinobacteria and 19% to Firmicutes. Diffusion agar assays for bioactivity screening against four bacterial strains and one yeast, revealed that a high number of the isolated bacteria (68.7%) were active, particularly against Candida albicans and Vibrio anguillarum. Pseudoalteromonas, Microbacterium, and Proteus were the most bioactive genera. After this preliminary screening, the bioactive strains were further evaluated in liquid assays against C. albicans, Bacillus subtilis and Escherichia coli. Filtered culture medium and acetone extracts from three and 5 days-old cultures were assayed. High antifungal activity against C. albicans in both aqueous and acetone extracts as well as absence of activity against B. subtilis were confirmed. Higher levels of activity were obtained with the aqueous extracts when compared to the acetone extracts and differences were also observed between the 3 and 5 day-old extracts. Furthermore, a low number of active strains was observed against E. coli. Potential presence of type-I polyketide synthases (PKS-I) and non-ribosomal peptide synthetases (NRPSs) genes were detected in 17 and 30 isolates, respectively. The high levels of bioactivity and the likely presence of associated genes suggest that Erylus deficiens bacteria are potential sources of novel marine bioactive compounds.

The marine actinomycete genus Salinispora: a model organism for secondary metabolite discovery

This review covers the initial discovery of the marine actinomycete genus Salinispora through its development as a model for natural product research. A focus is placed on the novel chemical structures reported with reference to their biological activities and the synthetic and biosynthetic studies they have inspired. The time line of discoveries progresses from more traditional bioassay-guided approaches through the application of genome mining and genetic engineering techniques that target the products of specific biosynthetic gene clusters. This overview exemplifies the extraordinary biosynthetic diversity that can emanate from a narrowly defined genus and supports future efforts to explore marine taxa in the search for novel natural products.

In-vitro antimicrobial activity of marine actinobacteria against multidrug resistance Staphylococcus aureus

OBJECTIVE

To investigate the antibacterial activity of marine actinobacteria against multidrug resistance Staphylococcus aureus (MDRSA).

METHODS

Fifty one actinobacterial strains were isolated from salt pans soil, costal area in Kothapattanam, Ongole, Andhra Pradesh. Primary screening was done using cross-streak method against MDRSA. The bioactive compounds are extracted from efficient actinobacteria using solvent extraction. The antimicrobial activity of crude and solvent extracts was performed using Kirby-Bauer method. MIC for ethyl acetate extract was determined by modified agar well diffusion method. The potent actinobacteria are identified using Nonomura key, Shirling and Gottlieb 1966 with Bergey's manual of determinative bacteriology.

RESULTS

Among the fifty one isolates screened for antibacterial activity, SRB25 were found efficient against MDRSA. The ethyl acetate extracts showed high inhibition against test organism. MIC test was performed with the ethyl acetate extract against MDRSA and found to be 1 000 µg/mL. The isolated actinobacteria are identified as Streptomyces sp with the help of Nonomura key.

CONCLUSIONS

The current investigation reveals that the marine actinobacteria from salt pan environment can be able to produce new drug molecules against drug resistant microorganisms.

Production of polysaccharide-based bioflocculant for the synthesis of silver nanoparticles by Streptomyces sp

Polysaccharide-based bioflocculants have attracted considerable attention in recent years due to their biodegradable, harmless and negligible secondary pollution. Bioflocculants are organic macromolecular substances secreted by microorganisms. A simple, cost-effective and green method was developed for the biosynthesis of silver nanoparticles using polysaccharides as reducing and stabilizing agents. In this paper, we report on the production and optimization of polysaccharide-based bioflocculant for the green synthesis of silver nanoparticles by Streptomyces sp. MBRC-91. Medium composition and culture conditions for polysaccharide-based bioflocculants were statistically optimized by response surface methodology (RSM). The bioflocculant production was statistically optimized with most significant factors, namely palm jaggery (18.73g/L), yeast extract (2.07g/L), K2HPO4 (3.74g/L) and NaCl (0.38g/L), respectively. The biosynthesized silver nanoparticles were characterized by UV-vis spectroscopy, XRD, FTIR, FESEM, EDXA and HRTEM. The biosynthesized silver nanoparticles revealed strong antibacterial activity in sewage water and this result could make a new avenue in the wastewater treatment. Therefore, the biosynthesized silver nanoparticles can be extended as an alternative for the development of new bactericidal bionanomaterials for wastewater treatment and biotechnological applications.

Metaphylogenomic and potential functionality of the limpet Patella pellucida's gastrointestinal tract microbiome

This study investigated the microbial diversity associated with the digestive tract of the seaweed grazing marine limpet Patella pellucida. Using a modified indirect DNA extraction protocol and performing metagenomic profiling based on specific prokaryotic marker genes, the abundance of bacterial groups was identified from the analyzed metagenome. The members of three significantly abundant phyla of Proteobacteria, Firmicutes and Bacteroidetes were characterized through the literature and their predicted functions towards the host, as well as potential applications in the industrial environment assessed.

Streptomyces bohaiensis sp. nov., a novel actinomycete isolated from Scomberomorus niphonius in the Bohai Sea

A novel actinomycete strain, designated 11A07(T), was isolated from young Scomberomorus niphonius in the Bohai Sea. Basic local alignment search tool analyses showed that this isolate had the highest 16S rRNA gene sequence similarity of 97.41% with Streptomyces rimosus subsp. paromomycinus DSM 41429(T). Phylogenetic tree revealed that strain 11A07(T) formed a distinct lineage clustered with Streptomyces panacagri Gsoil 519(T), Streptomyces sodiiphilus YIM 80305(T) and Streptomyces albus subsp. albus NRRL B-2365(T) having similarities of 97.30%, 97.10% and 96.83%, respectively. Multilocus sequence analysis further demonstrated that the new isolate was different from the selected representatives of Streptomyces as a separate phylogenetic line. Strain 11A07(T) produced straight or rectiflexibile spore chains with smooth surface, white aerial mycelia and brown diffusible pigments on international streptomyces project 2 medium. Maximum tolerated NaCl concentration for growth was 11.0%. Whole-cell sugars were mannose, ribose, glucose, galactose and xylose. The predominant menaquinones were MK-9(H2), MK-9(H4) and MK-9 (H6). The fatty-acid profile contained iso-C16:0, C18:0 10-methyl (tuberculostearic acid) and anteiso-C17:0 as the major compositions. The polar lipids consisted of diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylinositol, phosphatidylinositol mannoside and an unknown phospholipid. The G+C content of the genomic DNA was 71.4 mol%. These morphological, phenotypic and chemotaxonomic properties showed that strain 11A07(T) could be readily distinguished from the most closely related members of the genus Streptomyces. Thus, based on the polyphasic taxonomic data, strain 11A07(T) (=JCM 19630(T)=CCTCC AA 2013020(T)=KCTC 29263(T)) represents a novel species within the genus Streptomyces, for which the name Streptomyces bohaiensis sp. nov. is proposed.

Indimicins A-E, Bisindole Alkaloids from the Deep-Sea-Derived Streptomyces sp. SCSIO 03032

Five new bisindole alkaloids, indimicins A-E (1-5), bearing a unique 1',3'-dimethyl-2'-hydroindole moiety, were isolated from the marine-derived Streptomyces sp. SCSIO 03032, along with two new compounds, lynamicins F and G (6 and 7). Their planar structures were elucidated by detailed interpretation of their MS and NMR spectroscopic data, and the absolute configurations were determined by X-ray crystallographic analysis (for 1), comparison of CD spectra (for 2-4), and quantum chemical calculations (for 5). Indimicin B (2) exhibited moderate cytotoxic activity toward the MCF-7 cell line.