Antimicrobial compounds from seaweeds-associated bacteria and fungi

Characterization of Chitosan Hydrogels Obtained through Phenol and Tripolyphosphate Anionic Crosslinking

Chitosan is a deacetylated polymer of chitin that is extracted mainly from the exoskeleton of crustaceans and is the second-most abundant polymer in nature. Chitosan hydrogels are preferred for a variety of applications in bio-related fields due to their functional properties, such as antimicrobial activity and wound healing effects; however, the existing hydrogelation methods require toxic reagents and exhibit slow gelation times, which limit their application in biological fields. Therefore, a mild and rapid gelation method is necessary. We previously demonstrated that the visible light-induced gelation of chitosan obtained through phenol crosslinking (ChPh) is a rapid gelation method. To further advance this method (<10 s), we propose a dual-crosslinked chitosan hydrogel obtained by crosslinking phenol groups and crosslinking sodium tripolyphosphate (TPP) and the amino groups of chitosan. The chitosan hydrogel was prepared by immersing the ChPh hydrogel in a TPP solution after phenol crosslinking via exposure to visible light. The physicochemical properties of the dual-crosslinked hydrogels, including Young's moduli and water retentions, were subsequently investigated. Young's moduli of the dual-crosslinked hydrogels were 20 times higher than those of the hydrogels without TPP ion crosslinking. The stiffness could be manipulated by varying the immersion time, and the water retention properties of the ChPh hydrogel were improved by TPP crosslinking. Ion crosslinking could be reversed using an iron chloride solution. This method facilitates chitosan hydrogel use for various applications, particularly tissue engineering and drug delivery.

Natural Products and Pharmacological Properties of Symbiotic Bacillota (Firmicutes) of Marine Macroalgae

The shift from the terrestrial to the marine environment to discover natural products has given rise to novel bioactive compounds, some of which have been approved for human medicine. However, the ocean, which makes up nearly three-quarters of the Earth's surface, contains macro- and microorganisms whose natural products are yet to be explored. Among these underexplored marine organisms are macroalgae and their symbiotic microbes, such as Bacillota, a phylum of mostly Gram-positive bacteria previously known as Firmicutes. Macroalgae-associated Bacillota often produce chemical compounds that protect them and their hosts from competitive and harmful rivals. Here, we summarised the natural products made by macroalgae-associated Bacillota and their pharmacological properties. We discovered that these Bacillota are efficient producers of novel biologically active molecules. However, only a few macroalgae had been investigated for chemical constituents of their Bacillota: nine brown, five red and one green algae. Thus, Bacillota, especially from the marine habitat, should be investigated for potential pharmaceutical leads. Moreover, additional diverse biological assays for the isolated molecules of macroalgae Bacillota should be implemented to expand their bioactivity profiles, as only antibacterial properties were tested for most compounds.

No bacterial-mediated alleviation of thermal stress in a brown seaweed suggests the absence of ecological bacterial rescue effects

While microbiome alterations are increasingly proposed as a rapid mechanism to buffer organisms under changing environmental conditions, studies of these processes in the marine realm are lagging far behind their terrestrial counterparts. Here, we used a controlled laboratory experiment to examine whether the thermal tolerance of the brown seaweed Dictyota dichotoma, a common species in European coastal ecosystems, could be enhanced by the repeated addition of bacteria from its natural environment. Juvenile algae from three genotypes were subjected for two weeks to a temperature gradient, spanning almost the entire thermal range that can be tolerated by the species (11-30 °C). At the start of the experiment and again in the middle of the experiment, the algae were inoculated with bacteria from their natural environment or left untouched as a control. Relative growth rate was measured over the two-week period, and we assessed bacterial community composition prior to and at the end of the experiment. Since the growth of D. dichotoma over the full thermal gradient was not affected by supplementing bacteria, our results indicate no scope for bacterial-mediated stress alleviation. The minimal changes in the bacterial communities linked to bacterial addition, particularly at temperatures above the thermal optimum (22-23 °C), suggest the existence of a barrier to bacterial recruitment. These findings indicate that ecological bacterial rescue is unlikely to play a role in mitigating the effects of ocean warming on this brown seaweed.

Microbial Natural Products with Antiviral Activities, Including Anti-SARS-CoV-2: A Review

The SARS-CoV-2 virus, which caused the COVID-19 infection, was discovered two and a half years ago. It caused a global pandemic, resulting in millions of deaths and substantial damage to the worldwide economy. Currently, only a few vaccines and antiviral drugs are available to combat SARS-CoV-2. However, there has been an increase in virus-related research, including exploring new drugs and their repurposing. Since discovering penicillin, natural products, particularly those derived from microbes, have been viewed as an abundant source of lead compounds for drug discovery. These compounds treat bacterial, fungal, parasitic, and viral infections. This review incorporates evidence from the available research publications on isolated and identified natural products derived from microbes with anti-hepatitis, anti-herpes simplex, anti-HIV, anti-influenza, anti-respiratory syncytial virus, and anti-SARS-CoV-2 properties. About 131 compounds with in vitro antiviral activity and 1 compound with both in vitro and in vivo activity have been isolated from microorganisms, and the mechanism of action for some of these compounds has been described. Recent reports have shown that natural products produced by the microbes, such as aurasperone A, neochinulin A and B, and aspulvinone D, M, and R, have potent in vitro anti-SARS-CoV-2 activity, targeting the main protease (M^pro). In the near and distant future, these molecules could be used to develop antiviral drugs for treating infections and preventing the spread of disease.

Alterations in Epiphytic Bacterial Communities during the Occurrence of Green Rot Disease in Saccharina japonica Seedlings

Bacteria are one of the causes of green rot disease (GRD) in Saccharina japonica mariculture, which may lead to complete failure of seedling production. However, the association between bacterial community and host disease severity remains largely unknown. Therefore, in this study, the bacterial communities associated with GRD-infected seedlings with naturally varying disease severity from two seedling hatcheries in Northern China were analyzed to investigate the interactions between bacterial communities and GRD. The results indicated incorrect nutrient supply in both sites. Gammaproteobacteria, Alphaproteobacteria, and Bacteroidetes were prevalent in all samples. Significant structural alterations were detected for epibacterial communities, which were further evidenced by differently abundant bacterial taxa associated with seedlings with varying disease severity. The predicted pathways of bacterial adhesion and antimicrobial compounds biosynthesis were significantly enriched in less severely diseased seedlings, whereas glutathione metabolism and lipopolysaccharide biosynthesis were significantly increased in more severely diseased seedlings. The predicted categories of a two-component system, flagellar assembly, bacterial chemotaxis, and biofilm formation were significantly enriched in the bacterioplankton in more severely infected seawater. The differential bacterial community compositions and predicted functions provide new clues to elucidate the mechanism underlying the interaction between GRD occurrence and bacterial communities.

Composition and Functional Diversity of Epiphytic Bacterial and Fungal Communities on Marine Macrophytes in an Intertidal Zone

Marine macrophytes (seagrasses and macroalgae) and their epiphytic microorganisms play an important role in the ecological and biochemical processes of coastal oceans. However, simultaneous comparative studies on the biodiversity and functions of epiphytic bacteria and fungi associated with marine macrophytes have not been conducted. In this study, high-throughput sequencing technology was used to describe the epiphytic bacterial and fungal communities of 11 common macroalgae and 2 seagrasses from an intertidal zone of northern China and compare them with seawater communities. The results showed that Proteobacteria and Bacteroidota were the dominant bacterial phyla in marine macrophytes, whereas Ascomycota, Chytridiomycota, and Basidiomycota were the dominant fungal phyla. The alpha diversity of the bacterial and fungal communities in seagrasses was the highest of all macrophyte samples. This may have been related to their ability to recruit microorganisms from multiple sources. Host phylogeny may influence bacterial community structure, and geographical differences may influence fungal community structure. The FAPROTAX data indicated that C metabolic microbes were enriched in marine macrophytes, while the FUNGuild data indicated that undefined saprotroph, which participated in organic matter degradation, were also enriched in marine macrophytes. These findings provide a theoretical basis regarding the epiphytic microorganisms of macrophytes and may offer new insights to support the improved ecological restoration of seagrass and macroalgae beds.

Seaweeds' pigments and phenolic compounds with antimicrobial potential

Recently, there has been increased interest in the development of novel antimicrobial compounds for utilization in a variety of sectors, including pharmaceutical, biomedical, textile, and food. The use, overuse, and misuse of synthetic compounds or derivatives have led to an increase of pathogenic microorganisms gaining resistance to the traditional antimicrobial therapies, which has led to an increased need for alternative therapeutic strategies. Seaweed are marine organisms that can be cultivated sustainably, and they are a source of polar molecules, such as pigments and phenolic compounds, which demonstrated antimicrobial potential. This review focuses on current knowledge about pigments and phenolic compounds isolated from seaweeds, their chemical characteristics, antimicrobial bioactivity, and corresponding mechanism of action.

Optimization and Characterization of Antimicrobial Agents Produced by Marine Aspergillus terreus She05 against Aeromonas hydrophila and other Applications

Seven morphologically distinct marine fungi were isolated from sediment and Seawater samples at different sites along Alexandria seashore. Antagonism effect against Aeromonas hydrophila on purpose and other pathogen was estimated. The most promising isolate giving the highest antibacterial activity (14 mm) against A. hydrophila was morphologically and genetically identified as Aspergillus terreus SHE05 and the corresponding sequence was recorded in the GenBank database with accession no. MW772239. Time course production of the antibacterial agents by A. terreus SHE05 against A. hydrophila was studied showing the highest productivity after 5 days incubation. Multi-factorial design in terms of Placket Burman design was implemented to predict the critical factors influencing the production of the antibacterial agents by A. terreus SHE05 against A. hydrophila. The obtained results showed that malt extract, pH and temperature were the key factors affecting the antimicrobial activity. Consequently, Box-Behnken design was applied to estimate the optimized levels of each independent variable showing that the optimized conditions were malt extract, 3 (g/l); peptone, 0.75 (g/l); salinity, 50%; pH, 4; culture age, 4 days; inoculum size, 0.5 ml; temperature 30°C and incubation time 5 days, which caused an increase in the antimicrobial activity to 25 mm, which denotes an approximately 1.8 fold increase comparing with the pre-optimized conditions. The potentiality of chloroform, hexane, petroleum ether and ethyl acetate for extraction of the active compounds was tested showing that ethyl acetate was the best. The extracted bioactive metabolites using ethyl acetate were tested as antimicrobial, anticancer, antiviral and antioxidant agents. Results showed reasonable activities. GC-MS was used to recognize the active components in the ethyl acetate extract, showing that the major compound was the Dodecanamine, N,N-Dimethyl with RT 11.95, molecular weight 213, area % (55.46) and molecular formula C14H31N.

Evaluation of antimicrobial activity of bacterial symbionts isolated from wild field cockroach Blattella vaga from Saudi Arabia

Drug-resistant pathogens form the main threat to global health during the current century. Annually, a lot of patients die in hospitals due to infection with one or more drug-resistant bacteria especially Staphylococcus aureus (MRSA). In the absence of new effective antimicrobial drugs, the number of deaths said to be increased. Searching for new antibiotics in our backyard form a part of scientist strategies to solve such serious health problem. Insects consider one of such interesting sources of the new era of antimicrobial drugs. Cockroaches as an example can live and adapt in a polluted area for a long time, so through this work field cockroach, Blattella vaga was collected from two semi-wild areas around Riyadh, Saudi Arabia for isolation of gut bacteria searching for new antimicrobial agents. Three species of bacteria were identified from field cockroach gut: Bacillus licheniformis, Bacillus subtilis, and Kocuria rosea. The three species were isolated, purified, and tested for their antimicrobial activity against four drug-resistant pathogens (three bacteria: Salmonella enterica (ATCC25566), Staphylococcus aureus (MRSA) (Clinical strain), and Streptococcus mutans (RCMB 017(1) ATCC ® 25175™) and one fungus: Candida albicans (RCMB005003(1) ATCC® 10231™)). The results show no antimicrobial activity of Bacillus subtilis and very good activity Bacillus licheniformis and Kocuria rosea. Bacillus licheniformis gives very effective activity against Candida albicans while Kocuria rosea is effective against MRSA and Streptococcus mutans. None of the gut isolated bacteria show any activity against Salmonella enterica. Such results revealed that the metabolites of these bacteria could be used as substitutes to the already used antibiotics to overcome the problem of multidrug-resistant human pathogens.

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.

The Brown Seaweeds of Scotland, Their Importance and Applications

More than 50% of the UK coastline is situated in Scotland under legislative jurisdiction; therefore, there is a great opportunity for regionally focused economic development by the rational use of sustainable marine bio-sources. We review the importance of seaweeds in general, and more specifically, wrack brown seaweeds which are washed from the sea and accumulated in the wrack zone and their economic impact. Rules and regulations governing the harvesting of seaweed, potential sites for harvesting, along with the status of industrial application are discussed. We describe extraction and separation methods of natural products from these seaweeds along with their phytochemical profiles. Many potential applications for these derivatives exist in agriculture, energy, nutrition, biomaterials, waste treatment (composting), pharmaceuticals, cosmetics and other applications. The chemical diversity of the natural compounds present in these seaweeds is an opportunity to further investigate a range of chemical scaffolds, evaluate their biological activities, and develop them for better pharmaceutical or biotechnological applications. The key message is the significant opportunity for the development of high value products from a seaweed processing industry in Scotland, based on a sustainable resource, and locally regulated.

Current Understanding on Adhesion and Biofilm Development in Actinobacteria

Biofilm formation and microbial adhesion are two related and complex phenomena. These phenomena are known to play an important role in microbial life and various functions with positive and negative aspects. Actinobacteria have wide distribution in aquatic and terrestrial ecosystems. This phylum is very large and diverse and contains two important genera Streptomyces and Mycobacteria. The genus Streptomyces is the most biotechnologically important, while the genus Mycobacteria contains the pathogenic species of Mycobacteriaceae. According to the literature, the majority of studies carried out on actinomycetes are focused on the detection of new molecules. Despite the well-known diversity and metabolic activities, less attention has been paid to this phylum. Research on adhesion and biofilm formation is not well developed. In the present review, an attempt has been made to review the literature available on the different aspects on biofilm formation and adhesion of Actinobacteria. We focus especially on the genus Streptomyces. Furthermore, a brief overview about the molecules and structures involved in the adhesion phenomenon in the most relevant genus is summarized. We mention the mechanisms of quorum sensing and quorum quenching because of their direct association with biofilm formation.

Diversity, Ecological Role and Biotechnological Potential of Antarctic Marine Fungi

The Antarctic Ocean is one of the most remote and inaccessible environments on our planet and hosts potentially high biodiversity, being largely unexplored and undescribed. Fungi have key functions and unique physiological and morphological adaptations even in extreme conditions, from shallow habitats to deep-sea sediments. Here, we summarized information on diversity, the ecological role, and biotechnological potential of marine fungi in the coldest biome on Earth. This review also discloses the importance of boosting research on Antarctic fungi as hidden treasures of biodiversity and bioactive molecules to better understand their role in marine ecosystem functioning and their applications in different biotechnological fields.

Marine endophytic fungi associated with Halopteris scoparia (Linnaeus) Sauvageau as producers of bioactive secondary metabolites with potential dermocosmetic application

Marine fungi and, particularly, endophytic species have been recognised as one of the most prolific sources of structurally new and diverse bioactive secondary metabolites with multiple biotechnological applications. Despite the increasing number of bioprospecting studies, very few have already evaluated the cosmeceutical potential of marine fungal compounds. Thus, this study focused on a frequent seaweed in the Portuguese coast, Halopteris scoparia, to identify the endophytic marine fungi associated with this host, and assess their ability to biosynthesise secondary metabolites with antioxidative, enzymatic inhibitory (hyaluronidase, collagenase, elastase and tyrosinase), anti-inflammatory, photoprotective, and antimicrobial (Cutibacterium acnes, Staphylococcus epidermidis and Malassezia furfur) activities. The results revealed eight fungal taxa included in the Ascomycota, and in the most representative taxonomic classes in marine ecosystems (Eurotiomycetes, Sordariomycetes and Dothideomycetes). These fungi were reported for the first time in Portugal and in association with H. scoparia, as far as it is known. The screening analyses showed that most of these endophytic fungi were producers of compounds with relevant biological activities, though those biosynthesised by Penicillium sect. Exilicaulis and Aspergillus chevalieri proved to be the most promising ones for being further exploited by dermocosmetic industry. The chemical analysis of the crude extract from an isolate of A. chevalieri revealed the presence of two bioactive compounds, echinulin and neoechinulin A, which might explain the high antioxidant and UV photoprotective capacities exhibited by the extract. These noteworthy results emphasised the importance of screening the secondary metabolites produced by these marine endophytic fungal strains for other potential bioactivities, and the relevance of investing more efforts in understanding the ecology of halo/osmotolerant fungi.

The microbiota of intertidal macroalgae Fucus distichus is site-specific and resistant to change following transplant

It is unclear how host-associated microbial communities will be affected by future environmental change. Characterizing how microbiota differ across sites with varying environmental conditions and assessing the stability of the microbiota in response to abiotic variation are critical steps towards predicting outcomes of environmental change. Intertidal organisms are valuable study systems because they experience extreme variation in environmental conditions on tractable timescales such as tide cycles and across small spatial gradients in the intertidal zone. Here we show a widespread intertidal macroalgae, Fucus distichus, hosts site-specific microbiota over small (meters to kilometres) spatial scales. We demonstrate stability of site-specific microbial associations by manipulating the host environment and microbial species pool with common garden and reciprocal transplant experiments. We hypothesized that F. distichus microbiota would readily shift to reflect the contemporary environment due to selective filtering by abiotic conditions and/or colonization by microbes from the new environment or nearby hosts. Instead, F. distichus microbiota was stable for days after transplantation in both the laboratory and field. Our findings expand the current understanding of microbiota dynamics on an intertidal foundation species. These results may also point to adaptations for withstanding short-term environmental variation, in hosts and/or microbes, facilitating stable host-microbial associations.

Antagonistic Activity of Antimicrobial Metabolites Produced from Seaweed-Associated Bacillus amyloliquefaciens MTCC 10456 Against Malassezia spp

Members of the genus Malassezia are known to be opportunistic pathogens responsible for causing skin disorders such as seborrheic dermatitis or dandruff, pityriasis versicolor, folliculitis, atopic dermatitis, and psoriasis. Due to the side effects caused by prolonged use of current topical antifungal agents, development of an alternative treatment is necessary. Fermentative production of antimicrobial metabolites from Bacillus amyloliquefaciens MTCC 10456 was carried out, and their antagonistic activity against Malassezia furfur and Malassezia globosa was evaluated. The antifungal metabolites were isolated by acid precipitation, and bioassay-guided simultaneous separation of the antimicrobial compounds was done by reversed-phase high-performance liquid chromatography (RP-HPLC). The fraction which demonstrated antifungal activity consisted of bacilysin, homologues of bacillomycin D, and members of the macrolactin family. The presence of bacilysin was detected using specific inhibitor assays and homologues of bacillomycin D, and macrolactins were identified using liquid chromatography/high-resolution electrospray ionization-mass spectrometry (LC/HRESI-MS/MS) analysis. Synergism among the identified compounds was observed which enhanced the antagonistic activity against Malassezia spp. To our knowledge, this is the first study to report the co-production and separation of members of macrolactin antibiotics, lipopeptides such as bacillomycin D and dipeptide antibiotic bacilysin, by any Bacillus strain from marine environment. Activity of individual compounds against Malassezia has been reported which may facilitate their application in the field of dermatology and in cosmetic products.

Bioassay-Guided Fractionation and Antimicrobial Activities of Padina australis Extracts

Background: Marine seaweeds synthesize different metabolites with various biological activities, including antimicrobial effects. Objectives: The main object of this study was to fractionate the seaweed Padina australis and analyze the antimicrobial activities of these fractions to isolate the bioactive compounds. Methods: Padina australis was collected from the Persian Gulf and extracted by maceration with methanol-ethyl acetate solvent. The extract was evaporated and partitioned by the Kupchan method to yield hexane, dichloromethane, water, and butanol partitions. Dichloromethane partition was further fractionated by MPLC, and antimicrobial activity of the crude extracts and all fractions were investigated using disc diffusion and agar plate count methods. The MIC values of hexane, dichloromethane, chloroform, and butanol partitions and all fractions were calculated. Results: Fraction numbers 11, 4, and 7 showed the highest inhibitory effect with MIC value of 87 µg/mL, 156 µg/mL, and 156 µg/mL against E. coli, P. aeruginosa, and S. aureus, respectively. Conclusions: This study reveals that different fractions of P. australis have antimicrobial activities against various microorganisms.

Determinación de la capacidad antioxidante total de alimentos y plasma humano por fotoquimioluminiscencia: Correlación con ensayos fluorométricos (ORAC) y espectrofotométricos (FRAP)

La determinación de la capacidad antioxidante es útil para valorar la calidad de un alimento, la cantidad de antioxidantes presentes en un sistema, o la biodisponibilidad de compuestos antioxidantes en el cuerpo humano. Los métodos disponibles realizan la determinación del efecto potencial de las sustancias antioxidantes, presentes en los alimentos y en el organismo humano, contra las reacciones de oxidación. El objetivo fue comparar los resultados de la detección de la capacidad antioxidante total (CAT) en muestras de alimentos y plasma humano, mediante la quimioluminiscencia por fotosensibilización (PCL), en contraste con métodos que cuantifican la capacidad de absorbancia del radical de oxígeno (ORAC) y el poder antioxidante reductor del hierro (FRAP). Se obtuvieron extractos hidrosolubles y liposolubles de salvado de arroz estabilizado (SAE) y de harina de Ulva clathrata (HUC). El plasma se obtuvo de muestras de sangre humana (PHU). Se procesaron tres muestras en cada caso. Los resultados se analizaron mediante análisis de varianza de una vía y correlación de Pearson, p < 0.05. La CAT determinada mediante PCL fue: SAE 246.37 ± 5.37, HUC 21.05 ± 0.41 y PHU 90.59 ± 1.17 equivalentes Trolox (ET) μmol /100 g ó 100 mL, p < 0.05; ORAC: SAE 5015.62 ± 12.83, HUC 852.37 ± 3.45 y PHU 2563.31 ± 39.47 ET μmol /100 g ó 100 mL, p < 0.05. FRAP: SAE 519.37 ± 0.04, HUC 52.78 ± 0.01 y PHU 90.26 ± 0.01 equivalentes Fe2+ (EFe2+) µmol /100 g ó 100 mL. Se observaron correlaciones entre PCL y ORAC, r = 0.99; y la PCL y FRAP, r = 0.94, ambas estadísticamente significativas (p < 0.05). La PCL mostró ser un método confiable y alternativo para cuantificar la CAT, que se puede aplicar en estudios de alimentos y de intervenciones en salud.

Novel effective antibacterial small-molecules against Staphylococcus and Enterococcus strains

Background: Resistance developments against established antibiotics are an emerging problem for antibacterial therapies. Novel antibiotics are urgently needed. Materials & methods: We developed novel small-molecule antibacterials which are easily accessible in a simple one-pot synthesis. The central cyclopentaindole core is substituted with two indole residues. Various indole and cyclopentane substituents have been introduced. Additionally, first indole substituted propene compounds as ring-open variants of the cyclopentaindoles have been yielded and evaluated as antibacterials against Staphylococcus aureus and Enterococcus strains. Results: Most effective compounds have been those with a bromo cyclopentane and a chloro indole substitution. First lead compounds were identified with promising activities similar to that observed in vitro for last resort antibiotics, so that the novel compounds enriche the pool of perspective small-molecule antibacterial drug candidates.

The Screening and Evaluation of Fucus serratus and Fucus vesiculosus Extracts against Current Strains of MRSA Isolated from a Clinical Hospital Setting

Antimicrobial resistant strains of infection are afflicting clinical settings, driving the search for novel antimicrobial compounds. Naturally sourced bioactives, for instance those from seaweeds, have the potential to ameliorate this issue. As such, solvent extracts from the edible Irish seaweeds Fucus serratus and Fucus vesiculosus were screened for antimicrobial activity against 28 clinically isolated strains of MRSA, including one GISA (glycopeptide intermediate S. aureus) and two mecC gene containing strains. The water extract of F. vesiculosus was the most promising extract went on to be tested for biofilm prevention and disruption activity. The disk diffusion method was used to investigate the inhibition of the bacterial pathogens tested while MIC, MBC and biofilm disruption and prevention analyses were performed spectroscopically and by plate counts, respectively. Solvent extracts were found to have a wide array of antimicrobial activity against the strains tested, with the water extract from Fucus vesiculosus being the most promising. This extract was also found to both prevent and disrupt MRSA biofilms indicating the potential extract as new antimicrobials, and raising the possibility of their possible use in therapeutics.

Antitumor Potential of Seaweed Derived-Endophytic Fungi

The marine environment presents a high biodiversity and a valuable source of bioactive compounds with therapeutic and biotechnological potential. Among the organisms present in marine environment, the endophytic fungi isolated from seaweed stand out. These microorganisms have aroused interest in the scientific community regarding its various activities such as antiviral, antimicrobial, antioxidant, photoprotective, cytotoxic, genotoxic, anti-inflammatory, and anticancer, besides establishing important ecological relations with its hosts. Anticancer molecules derived from marine natural sources are a promising target against different types of cancer. The disease's high rates of morbidity and mortality affect millions of people world wild and the search for new therapeutic alternatives is needed. Thus, this review partially summarizes the methodologies for the isolation of seaweed-derived endophytic fungi, as well as describes the anticancer compounds isolated from such microorganisms, reported in the literature from 2009 to the present. In addition, it describes how some biotechnological processes can help in the discovery of bioactive compounds, especially with anticancer activity.

Chemically-Mediated Interactions Between Macroalgae, Their Fungal Endophytes, and Protistan Pathogens

Filamentous fungi asymptomatically colonize the inner tissues of macroalgae, yet their ecological roles remain largely underexplored. Here, we tested if metabolites produced by fungal endophytes might protect their host against a phylogenetically broad spectrum of protistan pathogens. Accordingly, the cultivable fungal endophytes of four brown algal species were isolated and identified based on LSU and SSU sequencing. The fungal metabolomes were tested for their ability to reduce the infection by protistan pathogens in the algal model Ectocarpus siliculosus. The most active metabolomes effective against the oomycetes Eurychasma dicksonii and Anisolpidium ectocarpii, and the phytomixid Maullinia ectocarpii were further characterized chemically. Several pyrenocines isolated from Phaeosphaeria sp. AN596H efficiently inhibited the infection by all abovementioned pathogens. Strikingly, these compounds also inhibited the infection of nori (Pyropia yezoensis) against its two most devastating oomycete pathogens, Olpidiopsis pyropiae, and Pythium porphyrae. We thus demonstrate that fungal endophytes associated with brown algae produce bioactive metabolites which might confer protection against pathogen infection. These results highlight the potential of metabolites to finely-tune the outcome of molecular interactions between algae, their endophytes, and protistan pathogens. This also provide proof-of-concept toward the applicability of such metabolites in marine aquaculture to control otherwise untreatable diseases.

Antiviral Agents From Fungi: Diversity, Mechanisms and Potential Applications

Viral infections are amongst the most common diseases affecting people worldwide. New viruses emerge all the time and presently we have limited number of vaccines and only few antivirals to combat viral diseases. Fungi represent a vast source of bioactive molecules, which could potentially be used as antivirals in the future. Here, we have summarized the current knowledge of fungi as producers of antiviral compounds and discuss their potential applications. In particular, we have investigated how the antiviral action has been assessed and what is known about the molecular mechanisms and actual targets. Furthermore, we highlight the importance of accurate fungal species identification on antiviral and other natural products studies.

Phylogeny and bioactivity of epiphytic Gram-positive bacteria isolated from three co-occurring antarctic macroalgae

Marine macroalgae are emerging as an untapped source of novel microbial diversity and, therefore, of new bioactive secondary metabolites. This study was aimed at assessing the diversity and antimicrobial activity of the culturable Gram-positive bacteria associated with the surface of three co-occurring Antarctic macroalgae. Specimens of Adenocystis utricularis (brown alga), Iridaea cordata (red alga) and Monostroma hariotii (green alga) were collected from the intertidal zone of King George Island, Antarctica. Gram-positive bacteria were investigated by cultivation-based methods and 16S rRNA gene sequencing, and screened for antimicrobial activity against a panel of pathogenic microorganisms. Isolates were found to belong to 12 families, with a dominance of Microbacteriaceae and Micrococcaceae. Seventeen genera of Actinobacteria and 2 of Firmicutes were cultured from the three macroalgae, containing 29 phylotypes. Three phylotypes within Actinobacteria were regarded as potentially novel species. Sixteen isolates belonging to the genera Agrococcus, Arthrobacter, Micrococcus, Pseudarthrobacter, Pseudonocardia, Sanguibacter, Staphylococcus, Streptomyces and Tessaracoccus exhibited antibiotic activity against at least one of the indicator strains. The bacterial phylotype composition was distinct among the three macroalgae species, suggesting that these macroalgae host species-specific Gram-positive associates. The results highlight the importance of Antarctic macroalgae as a rich source of Gram-positive bacterial diversity and potentially novel species, and a reservoir of bacteria producing biologically active compounds with pharmacological potential.

Phocoenamicins B and C, New Antibacterial Spirotetronates Isolated from a Marine Micromonospora sp

Phocoenamicins B and C (1 and 2), together with the known spirotetronate phocoenamicin (3), were isolated from cultures of Micromonospora sp. The acetone extract from a culture of this strain, isolated from marine sediments collected in the Canary Islands, displayed activity against methicillin-resistant Staphylococcus aureus (MRSA), Mycobacterium tuberculosis H37Ra and Mycobacterium bovis. Bioassay-guided fractionation of this extract using SP207ss column chromatography and preparative reversed-phased HPLC led to the isolation of the new compounds 1 and 2 belonging to the spirotetronate class of polyketides. Their structures were determined using a combination of HRMS, 1D and 2D NMR experiments and comparison with the spectra reported for phocoenamicin. Antibacterial activity tests of the pure compounds against these pathogens revealed minimal inhibitory concentration (MIC) values ranging from 4 to 64 µg/mL for MRSA, and 16 to 32 µg/mL for M. tuberculosis H37Ra, with no significant activity found against M. bovis and vancomycin-resistant Enterococcus faecium (VRE) at concentrations below 128 µg/mL, and weak activity detected against Bacillus subtilis grown on agar plates.

Isolation, purification, structural elucidation and antimicrobial activities of kocumarin, a novel antibiotic isolated from actinobacterium Kocuria marina CMG S2 associated with the brown seaweed Pelvetia canaliculata

AIMS

Screening of seaweed-associated bacteria capable of producing antimicrobials.

METHODS AND RESULTS

Fifteen microbial strains, associated to the brown seaweed Pelvetia canaliculata (Linnaeus) attached to the rocks of Sonmiani Beach (Karachi, Pakistan), were screened. Crude extract filtrates of CMG S2 strain grew on Zobell marine agar (ZMA) had the most remarkable antimicrobial activity. Based on its phenotypic aspects (e.g. Gram-positive, microccoid form), biochemical characteristics (e.g. halotolerance) and genetic analyses, CMG S2 is identified as a putatively new Kocuria marina type strain belonging to the actinobacteria's class and micrococcaceae family. Thereby, the nucleotide sequence analysis of its full-length 16S ribosomal ribonucleic acid (rRNA) gene (GenBank accession number EU073966.1) displayed highest identity (i.e. 99%) and score (2630) with K. marina KMM 3905. Phylogenic trees analysis using the neighbor-joining method showed closest evolutionary distance of CMG S2 with KMM 3905 strain and K. carniphila (DC2201) specie. Interestingly, a unique ultraviolet (UV)-bioactive compound was purified from CMG S2 crude extracts by flash silica gel column and thin-layer chromatography (TLC) techniques. Its chemical structure was unraveled as 4-[(Z)-2 phenyl ethenyl] benzoic acid (PEBA, later named kocumarin) by nuclear magnetic resonance (NMR) spectroscopy techniques. Importantly, kocumarin demonstrated prominent and rapid growth inhibition against all tested fungi and pathogenic bacteria including methicillin-resistant Staphylococcus aureus (MRSA), with a minimal fungal inhibitory concentration (MFC) of 15-25μg/mL and a minimal (bacterial) inhibitory concentration (MIC) of 10-15μg/mL.

SIGNIFICANCE AND IMPACT OF THE STUDY

Kocumarin represents a new promising natural antibiotic for in vivo and environmental applications.

Antiviral Agents From Fungi: Diversity, Mechanisms and Potential Applications

Viral infections are amongst the most common diseases affecting people worldwide. New viruses emerge all the time and presently we have limited number of vaccines and only few antivirals to combat viral diseases. Fungi represent a vast source of bioactive molecules, which could potentially be used as antivirals in the future. Here, we have summarized the current knowledge of fungi as producers of antiviral compounds and discuss their potential applications. In particular, we have investigated how the antiviral action has been assessed and what is known about the molecular mechanisms and actual targets. Furthermore, we highlight the importance of accurate fungal species identification on antiviral and other natural products studies.

Minireview: algal natural compounds and extracts as antifoulants

Marine biofouling is a paramount phenomenon in the marine environment and causes serious problems to maritime industries worldwide. Marine algae are known to produce a wide variety of chemical compounds with antibacterial, antifungal, antialgal, and anti-macrofouling properties, inhibiting the settlement and growth of other marine fouling organisms. Significant investigations and progress have been made in this field in the last two decades and several antifouling extracts and compounds have been isolated from micro- and macroalgae. In this minireview, we have summarized and evaluated antifouling compounds isolated and identified from macroalgae and microalgae between January 2010 and June 2016. Future directions for their commercialization through metabolic engineering and industrial scale up have been discussed. Upon comparing biogeographical regions, investigations from Southeast Asian waters were found to be rather scarce. Thus, we have also discussed the need to conduct more chemical ecology based research in relatively less explored areas with high algal biodiversity like Southeast Asia.

Antifungal potential of marine natural products

Fungal diseases represent an increasing threat to human health worldwide which in some cases might be associated with substantial morbidity and mortality. However, only few antifungal drugs are currently available for the treatment of life-threatening fungal infections. Furthermore, plant diseases caused by fungal pathogens represent a worldwide economic problem for the agriculture industry. The marine environment continues to provide structurally diverse and biologically active secondary metabolites, several of which have inspired the development of new classes of therapeutic agents. Among these secondary metabolites, several compounds with noteworthy antifungal activities have been isolated from marine microorganisms, invertebrates, and algae. During the last fifteen years, around 65% of marine natural products possessing antifungal activities have been isolated from sponges and bacteria. This review gives an overview of natural products from diverse marine organisms that have shown in vitro and/or in vivo potential as antifungal agents, with their mechanism of action whenever applicable. The natural products literature is covered from January 2000 until June 2015, and we are reporting the chemical structures together with their biological activities, as well as the isolation source.

Application of seaweeds to develop new food products with enhanced shelf-life, quality and health-related beneficial properties

Edible seaweeds are a good source of antioxidants, dietary fibers, essential amino acids, vitamins, phytochemicals, polyunsaturated fatty acids, and minerals. Many studies have evaluated the gelling, thickening and therapeutic properties of seaweeds when they are used individually. This review gives an overview on the nutritional, textural, sensorial, and health-related properties of food products enriched with seaweeds and seaweed extracts. The effect of seaweed incorporation on properties of meat, fish, bakery, and other food products were highlighted in depth. Moreover, the positive effects of foods enriched with seaweeds and seaweed extracts on different lifestyle diseases such as obesity, dyslipidemia, hypertension, and diabetes were also discussed. The results of the studies demonstrated that the addition of seaweeds, in powder or extract form, can improve the nutritional and textural properties of food products. Additionally, low-fat products with less calories and less saturated fatty acids can be prepared using seaweeds. Moreover, the addition of seaweeds also affected the health properties of food products. The results of these studies demonstrated that the health value, shelf-life and overall quality of foods can be improved through the addition of either seaweeds or seaweed extracts.

Surface metabolites of the brown alga Taonia atomaria have the ability to regulate epibiosis

This study aimed to improve understanding of the strategies developed by the Mediterranean seaweed Taonia atomaria to chemically control bacterial epibiosis. An experimental protocol was optimized to specifically extract algal surface-associated metabolites by a technique involving dipping in organic solvents whilst the integrity of algal cell membranes was assessed by fluorescent microscopy. This methodology was validated using mass spectrometry-based profiles of algal extracts and analysis of their principal components, which led to the selection of methanol as the extraction solvent with a maximum exposure time of 15 s. Six compounds (A-F) were identified in the resulting surface extracts. Two of these surface-associated compounds (B and C) showed selective anti-adhesion properties against reference bacterial strains isolated from artificial surfaces while remaining inactive against epibiotic bacteria of T. atomaria. Such specificity was not observed for commercial antifouling biocides and other molecules identified in the surface or whole-cell extracts of T. atomaria.

Spotlight on Antimicrobial Metabolites from the Marine Bacteria Pseudoalteromonas: Chemodiversity and Ecological Significance

This review is dedicated to the antimicrobial metabolite-producing Pseudoalteromonas strains. The genus Pseudoalteromonas hosts 41 species, among which 16 are antimicrobial metabolite producers. To date, a total of 69 antimicrobial compounds belonging to 18 different families have been documented. They are classified into alkaloids, polyketides, and peptides. Finally as Pseudoalteromonas strains are frequently associated with macroorganisms, we can discuss the ecological significance of antimicrobial Pseudoalteromonas as part of the resident microbiota.

Antimicrobial Action of Compounds from Marine Seaweed

Seaweed produces metabolites aiding in the protection against different environmental stresses. These compounds show antiviral, antiprotozoal, antifungal, and antibacterial properties. Macroalgae can be cultured in high volumes and would represent an attractive source of potential compounds useful for unconventional drugs able to control new diseases or multiresistant strains of pathogenic microorganisms. The substances isolated from green, brown and red algae showing potent antimicrobial activity belong to polysaccharides, fatty acids, phlorotannins, pigments, lectins, alkaloids, terpenoids and halogenated compounds. This review presents the major compounds found in macroalga showing antimicrobial activities and their most promising applications.

Antibacterial and antifungal compounds from marine fungi

This paper reviews 116 new compounds with antifungal or antibacterial activities as well as 169 other known antimicrobial compounds, with a specific focus on January 2010 through March 2015. Furthermore, the phylogeny of the fungi producing these antibacterial or antifungal compounds was analyzed. The new methods used to isolate marine fungi that possess antibacterial or antifungal activities as well as the relationship between structure and activity are shown in this review.