Marine Actinobacteria a New Source of Antibacterial Metabolites to Treat Acne Vulgaris Disease—A Systematic Literature Review

Acne vulgaris is a multifactorial disease that remains under-explored; up to date it is known that the bacterium Cutibacterium acnes is involved in the disease occurrence, also associated with a microbial dysbiosis. Antibiotics have become a mainstay treatment generating the emergence of antibiotic-resistant bacteria. In addition, there are some reported side effects of alternative treatments, which indicate the need to investigate a different therapeutic approach. Natural products continue to be an excellent option, especially those extracted from actinobacteria, which represent a prominent source of metabolites with a wide range of biological activities, particularly the marine actinobacteria, which have been less studied than their terrestrial counterparts. Therefore, this systematic review aimed to identify and evaluate the potential anti-infective activity of metabolites isolated from marine actinobacteria strains against bacteria related to the development of acne vulgaris disease. It was found that there is a variety of compounds with anti-infective activity against Staphylococcus aureus and Staphylococcus epidermidis, bacteria closely related to acne vulgaris development; nevertheless, there is no report of a compound with antibacterial activity or quorum-sensing inhibition toward C. acnes, which is a surprising result. Since two of the most widely used antibiotics for the treatment of acne targeting C. acnes were obtained from actinobacteria of the genus Streptomyces, this demonstrates a great opportunity to pursue further studies in this field, considering the potential of marine actinobacteria to produce new anti-infective compounds.

Microbial diversity in Mediterranean sponges as revealed by metataxonomic analysis

Although the Mediterranean Sea covers approximately a 0.7% of the world's ocean area, it represents a major reservoir of marine and coastal biodiversity. Among marine organisms, sponges (Porifera) are a key component of the deep-sea benthos, widely recognized as the dominant taxon in terms of species richness, spatial coverage, and biomass. Sponges are evolutionarily ancient, sessile filter-feeders that harbor a largely diverse microbial community within their internal mesohyl matrix. In the present work, we firstly aimed at exploring the biodiversity of marine sponges from four different areas of the Mediterranean: Faro Lake in Sicily and "Porto Paone", "Secca delle fumose", "Punta San Pancrazio" in the Gulf of Naples. Eight sponge species were collected from these sites and identified by morphological analysis and amplification of several conserved molecular markers (18S and 28S RNA ribosomal genes, mitochondrial cytochrome oxidase subunit 1 and internal transcribed spacer). In order to analyze the bacterial diversity of symbiotic communities among these different sampling sites, we also performed a metataxonomic analysis through an Illumina MiSeq platform, identifying more than 1500 bacterial taxa. Amplicon Sequence Variants (ASVs) analysis revealed a great variability of the host-specific microbial communities. Our data highlight the occurrence of dominant and locally enriched microbes in the Mediterranean, together with the biotechnological potential of these sponges and their associated bacteria as sources of bioactive natural compounds.

Reclassification of Streptomyces diastaticus subsp. ardesiacus, Streptomyces gougerotii and Streptomyces rutgersensis

We investigated the taxonomic relationships among Streptomyces diastaticus subsp. ardesiacus, Streptomyces diastaticus subsp. diastaticus, Streptomyces gougerotii and Streptomyces rutgersensis. The 16S rRNA gene sequence similarity between S. diastaticus subsp. ardesiacus and S. diastaticus subsp. diastaticus was 97.7 %, whereas S. diastaticus subsp. diastaticus, S. gougerotii and S. rutgersensis showed 100 % nucleotide sequence identity. In addition, S. diastaticus subsp. diastaticus, S. gougerotii and S. rutgersensis formed a single clade in the phylogenetic tree. Digital DNA-DNA relatedness between S. diastaticus subsp. diastaticus and S. diastaticus subsp. ardesiacus was only 22.8%, indicative of different species. In comparison, DNA-DNA relatedness values for S. diastaticus subsp. diastaticus, S. gougerotii and S. rutgersensis ranged from 95.8 to 97.2 %, suggesting the three taxa belong to the same genomospecies. Previously reported phenotypic data also supported synonymy. Therefore, we propose that S. diastaticus subsp. ardesiacus should be classified as an independent species, Streptomyces ardesiacus sp. nov. The type strain is NBRC 13412^T (=ATCC 3315^T=CBS 713.72^T=DSM 40496^T=ISP 5496^T=JCM 4745^T=NBRC 3714^T=NRRL B-1241^T=RIA 1373^T). Our data also suggests that S. rutgersensis and S. gougerotii should be reclassified as later heterotypic synonyms of S. diastaticus.

Metagenomic Exploration of the Marine Sponge Mycale hentscheli Uncovers Multiple Polyketide-Producing Bacterial Symbionts

Marine sponges have been a prolific source of unique bioactive compounds that are presumed to act as a deterrent to predation. Many of these compounds have potential therapeutic applications; however, the lack of efficient and sustainable synthetic routes frequently limits clinical development. Here, we describe a metagenomic investigation of Mycale hentscheli, a chemically gifted marine sponge that possesses multiple distinct chemotypes. We applied shotgun metagenomic sequencing, hybrid assembly of short- and long-read data, and metagenomic binning to obtain a comprehensive picture of the microbiome of five specimens, spanning three chemotypes. Our data revealed multiple producing species, each having relatively modest secondary metabolomes, that contribute collectively to the chemical arsenal of the holobiont. We assembled complete genomes for multiple new genera, including two species that produce the cytotoxic polyketides pateamine and mycalamide, as well as a third high-abundance symbiont harboring a proteusin-type biosynthetic pathway that appears to encode a new polytheonamide-like compound. We also identified an additional 188 biosynthetic gene clusters, including a pathway for biosynthesis of peloruside. These results suggest that multiple species cooperatively contribute to defensive symbiosis in M. hentscheli and reveal that the taxonomic diversity of secondary-metabolite-producing sponge symbionts is larger and richer than previously recognized.IMPORTANCE Mycale hentscheli is a marine sponge that is rich in bioactive small molecules. Here, we use direct metagenomic sequencing to elucidate highly complete and contiguous genomes for the major symbiotic bacteria of this sponge. We identify complete biosynthetic pathways for the three potent cytotoxic polyketides which have previously been isolated from M. hentscheli Remarkably, and in contrast to previous studies of marine sponges, we attribute each of these metabolites to a different producing microbe. We also find that the microbiome of M. hentscheli is stably maintained among individuals, even over long periods of time. Collectively, our data suggest a cooperative mode of defensive symbiosis in which multiple symbiotic bacterial species cooperatively contribute to the defensive chemical arsenal of the holobiont.

Antimicrobial profiling of coral reef and sponge associated bacteria from southeast coast of India

Culturable bacteria associated with marine sponges and coral mucus (collected from Gulf of Mannar and Palk Bay) were screened for their prospective antimicrobial compounds against 9 bacterial pathogens (Bacillus megaterium, B. cereus, Salmonella typhimurium, Staphylococcus aureus, Proteus vulgaris, Klebsillla pneumoniae, Escherichia coli, Pseudomonas aeruginosa and Acinetobacter baumannii) and a fungal pathogen (Candida albicans). Of the 263 bacterial isolates obtained during this study, 52 isolates displayed antimicrobial activity against one or more pathogens. 16S rRNA gene sequencing revealed that these 52 strains affiliated to 14 genera from three phyla Proteobacteria, Firmicutes and Actinobacteria. Sponge associated bacterial strains F-04, I-23, I-33 and G-03 inhibited the growth of all the bacterial pathogens tested in this study and significantly the former 2 strains inhibited the growth of fungal pathogen also. Majority of the potential strains (88.4% out of 52 strains) inhibited the growth of Bacillus cereus. Interestingly, an actinomycete strain F-04 (isolated from sponge Orina sagittaria) inhibited the growth of methicillin resistant Staphylococcus aureus. In total, 10 volatile organic compounds were determined from the ethyl acetate and hexane extract of the strain F-04 using GC-MS. Overall, marine bacteria isolated during this study demonstrate the potential for the development of broad spectrum antibiotics.

Loci Encoding Compounds Potentially Active against Drug-Resistant Pathogens amidst a Decreasing Pool of Novel Antibiotics

Carbapenem-resistant P. aeruginosa is difficult to treat and has been deemed by the World Health Organization as a priority one pathogen for which antibiotics are most urgently needed. Although metagenomics and bioinformatic studies suggest that natural bacteria remain a source of novel compounds, the identification of genes and their products specific to activity against MDR pathogens remains problematic. Here, we examine water-derived pseudomonads and identify gene clusters whose compounds inhibit CF-derived MDR pathogens, including carbapenem-resistant P. aeruginosa.

Since the discovery of penicillin, microbes have been a source of antibiotics that inhibit the growth of pathogens. However, with the evolution of multidrug-resistant (MDR) strains, it remains unclear if there is an abundant or limited supply of natural products to be discovered that are effective against MDR isolates. To identify strains that are antagonistic to pathogens, we examined a set of 471 globally derived environmental Pseudomonas strains (env-Ps) for activity against a panel of 65 pathogens including Achromobacter spp., Burkholderia spp., Pseudomonas aeruginosa, and Stenotrophomonas spp. isolated from the lungs of cystic fibrosis (CF) patients. From more than 30,000 competitive interactions, 1,530 individual inhibitory events were observed. While strains from water habitats were not proportionate in antagonistic activity, MDR CF-derived pathogens (CF-Ps) were less susceptible to inhibition by env-Ps, suggesting that fewer natural products are effective against MDR strains. These results advocate for a directed strategy to identify unique drugs. To facilitate discovery of antibiotics against the most resistant pathogens, we developed a workflow in which phylogenetic and antagonistic data were merged to identify strains that inhibit MDR CF-Ps and subjected those env-Ps to transposon mutagenesis. Six different biosynthetic gene clusters (BGCs) were identified from four strains whose products inhibited pathogens including carbapenem-resistant P. aeruginosa. BGCs were rare in databases, suggesting the production of novel antibiotics. This strategy can be utilized to facilitate the discovery of needed antibiotics that are potentially active against the most drug-resistant pathogens.

IMPORTANCE Carbapenem-resistant P. aeruginosa is difficult to treat and has been deemed by the World Health Organization as a priority one pathogen for which antibiotics are most urgently needed. Although metagenomics and bioinformatic studies suggest that natural bacteria remain a source of novel compounds, the identification of genes and their products specific to activity against MDR pathogens remains problematic. Here, we examine water-derived pseudomonads and identify gene clusters whose compounds inhibit CF-derived MDR pathogens, including carbapenem-resistant P. aeruginosa.

Complete Genome Sequence of Streptomyces sp. Strain BSE7F, a Bali Mangrove Sediment Actinobacterium with Antimicrobial Activities

The strain Streptomyces sp. BSE7F, a novel Streptomyces strain isolated from Indonesian mangrove sediment, displays antimicrobial activities against Gram-positive bacteria, Gram-negative bacteria, and yeast.

The strain Streptomyces sp. BSE7F, a novel Streptomyces strain isolated from Indonesian mangrove sediment, displays antimicrobial activities against Gram-positive bacteria, Gram-negative bacteria, and yeast. Bioinformatic analysis of the genome sequence revealed the occurrence of 22 biosynthetic gene clusters disclosing the secondary metabolite capacity of strain BSE7F.

Aquatic Pseudomonads Inhibit Oomycete Plant Pathogens of Glycine max

Seedling root rot of soybeans caused by the host-specific pathogen Phytophthora sojae, and a large number of Pythium species, is an economically important disease across the Midwest United States that negatively impacts soybean yields. Research on biocontrol strategies for crop pathogens has focused on compounds produced by microbes from soil, however, recent studies suggest that aquatic bacteria express distinct compounds that efficiently inhibit a wide range of pathogens. Based on these observations, we hypothesized that freshwater strains of pseudomonads might be producing novel antagonistic compounds that inhibit the growth of oomycetes. To test this prediction, we utilized a collection of 330 Pseudomonas strains isolated from soil and freshwater habitats, and determined their activity against a panel of five oomycetes: Phytophthora sojae, Pythium heterothalicum, Pythium irregulare, Pythium sylvaticum, and Pythium ultimum, all of which are pathogenic on soybeans. Among the bacterial strains, 118 exhibited antagonistic activity against at least one oomycete species, and 16 strains were inhibitory to all pathogens. Antagonistic activity toward oomycetes was significantly more common for aquatic isolates than for soil isolates. One water-derived strain, 06C 126, was predicted to express a siderophore and exhibited diverse antagonistic profiles when tested on nutrient rich and iron depleted media suggesting that more than one compound was produced that effectively inhibited oomycetes. These results support the concept that aquatic strains are an efficient source of compounds that inhibit pathogens. We outline a strategy to identify other strains that express unique compounds that may be useful biocontrol agents.

Quinazoline derivative from indigenous isolate, Nocardiopsis alba inhibits human telomerase enzyme

AIM

Aim of this study was isolation and screening of various secondary metabolites produced by indigenous isolates of soil Actinomycetes for human telomerase inhibitory activity.

METHODS AND RESULTS

Extracellular extract from culture suspension of various soil Actinomycetes species were tested for telomerase inhibitory activity. The organism which produced telomerase inhibitor was identified by 16S rRNA gene sequencing. The active fraction was purified by HPLC and analysed by GC-MS to identify the compound. In GC-MS analysis, the active principle was identified as 3-[4'-(2″-chlorophenyl)-2'-thiazolyl]-2,4-dioxo-1,2,3,4-tetrahydro quinazoline. The G-quadruplex stabilizing ability of the compound was checked by molecular docking and simulation experiments with G-quadruplex model (PDB ID-1L1H). The selective binding ability of the compound with G-quadruplex over Dickerson-Drew dodecamer DNA structures showed that the compound possess high selectivity towards G-quadruplex.

CONCLUSIONS

Quinazoline derivative isolated from an indigenous strain of Nocardiopsis alba inhibited telomerase. Molecular docking and simulation studies predicted that this compound is a strong stabilizer of G-quadruplex conformation. It also showed a preferable binding to G-quadruplex DNA over normal DNA duplex.

SIGNIFICANCE AND IMPACT OF THE STUDY

This particular compound can be suggested as a suitable compound for developing a future anticancer drug. The selectivity towards G-quadruplex over normal DNA duplex gives a clue that it is likely to show lower cytotoxicity in normal cells.

Bioprospecting Sponge-Associated Microbes for Antimicrobial Compounds

Sponges are the most prolific marine organisms with respect to their arsenal of bioactive compounds including antimicrobials. However, the majority of these substances are probably not produced by the sponge itself, but rather by bacteria or fungi that are associated with their host. This review for the first time provides a comprehensive overview of antimicrobial compounds that are known to be produced by sponge-associated microbes. We discuss the current state-of-the-art by grouping the bioactive compounds produced by sponge-associated microorganisms in four categories: antiviral, antibacterial, antifungal and antiprotozoal compounds. Based on in vitro activity tests, identified targets of potent antimicrobial substances derived from sponge-associated microbes include: human immunodeficiency virus 1 (HIV-1) (2-undecyl-4-quinolone, sorbicillactone A and chartarutine B); influenza A (H1N1) virus (truncateol M); nosocomial Gram positive bacteria (thiopeptide YM-266183, YM-266184, mayamycin and kocurin); Escherichia coli (sydonic acid), Chlamydia trachomatis (naphthacene glycoside SF2446A2); Plasmodium spp. (manzamine A and quinolone 1); Leishmania donovani (manzamine A and valinomycin); Trypanosoma brucei (valinomycin and staurosporine); Candida albicans and dermatophytic fungi (saadamycin, 5,7-dimethoxy-4-p-methoxylphenylcoumarin and YM-202204). Thirty-five bacterial and 12 fungal genera associated with sponges that produce antimicrobials were identified, with Streptomyces, Pseudovibrio, Bacillus, Aspergillus and Penicillium as the prominent producers of antimicrobial compounds. Furthemore culture-independent approaches to more comprehensively exploit the genetic richness of antimicrobial compound-producing pathways from sponge-associated bacteria are addressed.

Therapeutic Application of Synbiotics, a Fusion of Probiotics and Prebiotics, and Biogenics as a New Concept for Oral Candida Infections: A Mini Review

Candida is a major human fungal pathogen causing infectious conditions predominantly in the elderly and immunocompromised hosts. Although Candida resides as a member of the oral indigenous microbiota in symbiosis, some circumstances may cause microbial imbalance leading to dysbiosis and resultant oral candidiasis. Therefore, oral microbial symbiosis that suppresses the overgrowth of Candida is important for a healthy oral ecosystem. In this regard, probiotics, prebiotics, and synbiotics can be considered a potential therapeutic and preventive strategy against oral candidiasis. Prebiotics have a direct effect on microbial growth as they stimulate the growth of beneficial bacteria and suppress the growth of pathogens. Probiotics render a local protective effect against pathogens and a systemic indirect effect on immunological amelioration. Synbiotics are fusion products of prebiotics and probiotics. This mini review discusses the potential use and associated limitations of probiotics, prebiotics, and synbiotics for the prevention and treatment of oral candidiasis. We will also introduce biogenics, a recent concept derived from the work on probiotics. Biogenics advocates the use of beneficial bioactive substances produced by probiotic bacteria, whose activities are independent from the viability of probiotic bacteria in human bodies.