HR-LC-MS based analysis of two antibacterial metabolites from a marine sponge symbiont Streptomyces pharmamarensis ICN40

Bioprospecting of unexplored halophilic actinobacteria against human infectious pathogens

Human pathogenic diseases received much attention recently due to their uncontrolled spread of antimicrobial resistance (AMR) which causes several threads every year. Effective alternate antimicrobials are urgently required to combat those disease causing infectious microbes. Halophilic actinobacteria revealed huge potentials and unexplored cultivable/non-cultivable actinobacterial species producing enormous antimicrobials have been proved in several genomics approaches. Potential gene clusters, PKS and NRPKS from Nocardia, Salinospora, Rhodococcus, and Streptomyces have wide range coding genes of secondary metabolites. Biosynthetic pathways identification via various approaches like genome mining, In silico, OSMAC (one strain many compound) analysis provides better identification of knowing the active metabolites using several databases like AMP, APD and CRAMPR, etc. Genome constellations of actinobacteria particularly the prediction of BGCs (Biosynthetic Gene Clusters) to mine the bioactive molecules such as pigments, biosurfactants and few enzymes have been reported for antimicrobial activity. Saltpan, saltlake, lagoon and haloalkali environment exploring potential actinobacterial strains Micromonospora, Kocuria, Pseudonocardia, and Nocardiopsis revealed several acids and ester derivatives with antimicrobial potential. Marine sediments and marine macro organisms have been found as significant population holders of potential actinobacterial strains. Deadly infectious diseases (IDs) including tuberculosis, ventilator-associated pneumonia and Candidiasis, have been targeted by halo-actinobacterial metabolites with promising results. Methicillin resistant Staphylococus aureus and virus like Encephalitic alphaviruses were potentially targeted by halophilic actinobacterial metabolites by the compound Homoseongomycin from sponge associated antinobacterium. In this review, we discuss the potential antimicrobial properties of various biomolecules extracted from the unexplored halophilic actinobacterial strains specifically against human infectious pathogens along with prospective genomic constellations.

Bioefficacy of isolated compound l-isoleucine, N-allyloxycarbonyl-, and dodecyl ester from entomopathogenic actinobacteria Actinokineospora fastidiosa against agricultural insect pests, human vector mosquitoes, and antioxidant activities

Spodoptera litura and Helicoverpa armigera are polyphagous pests of agricultural crops in the Asian tropics since these pests have been responsible for massive crop and carry economic losses and low commodity production. At the same time, mosquitoes are vectors for numerous dreadful diseases, which is the most important group of insect for their public health concern. Using synthetic insecticides to control the pests can lead to contamination of land surface and groundwater and impact beneficial soil organisms and nontarget species. Applications of bioactive compounds are received considerable attention across the world as alternatives to synthetic insecticides. In the current study, actinobacterial secondary metabolite was isolated from Actinokineospora fastidiosa for the first time. The effect of actinobacterial metabolite (l-isoleucine, N-allyloxycarbonyl-, and dodecyl ester) was assessed on agricultural pest S. litura and H. armigera, mosquito vectors larvae Ae. aegypti, An. stephensi, and Cx. quinquefasciatus. The bioactive fraction was characterized through UV, FTIR, and NMR analysis. GC-MS analyses reveal the existence of a bioactive compound with a respective retention time of 19.740 responsible for larvicidal activity. The bioefficacy of the l-isoleucine, N-allyloxycarbonyl-, and dodecyl ester showed high antifeedant activity on S. litura (80.80%) and H. armigera (84.49%); and larvicidal activity on S. litura (82.77%) and H. armigera (88.00%) at 25 μg/mL concentration, respectively. The effective LC₅₀ values were 8.07 μg/mL (F = 2.487, r² = 0.988, P ≤ 0.05) on S. litura and 7.53 μg/mL (F = 123.25, r² = 0.951, P ≤ 0.05) on H. armigera. The mosquito larvicidal effect of isolated compounds l-isoleucine, N-allyloxycarbonyl-, and dodecyl ester treated against Ae. aegypti, An. stephensi, and Cx. quinquefasciatus the obtained percentage mortality was 96.66, 83.24, 64.52, 50.00, and 40.00% against Ae. aegypti; 100.00, 86.22, 73.81, 65.37, and 56.24% against An. stephensi; 100.00, 90.00, 76.24, 68.75, and 56.23% against Cx. quinquefasciatus. The mosquito larvae of Ae. aegypti obtained LC₅₀ value was 13.25 μg/mL, F = 28.50, r² = 0.90; on An. stephensi was 10.19 μg/mL, F = 15.55, r² = 0.83, and Cx. quinquefasciatus was 9.68 μg/mL, F = 20.00, r² = 0.87. Furthermore, l-isoleucine-, N-allyloxycarbonyl-, and dodecyl ester-treated larvae produced significant pupicidal activity on S. litura (62.71%) and H. armigera (66.50%) at 25 μg/mL, along with increased larval and pupal duration as compared to control group. Treated larvae revealed obliteration in the midgut epithelial cells and destruction of microvilli was noticed as compared to the control. The isolated compounds l-isoleucine, N-allyloxycarbonyl-, and dodecyl ester did not produce any significant mortality on zebrafish embryos in all tested concentrations on biosafety observation. The potential microbial isolated molecule may fit well in IPM programs. Since the risk to human health, the environment, etc. is unknown.

Overview on Strategies and Assays for Antibiotic Discovery

The increase in antibiotic resistance poses a major threat to global health. Actinomycetes, the Gram-positive bacteria of the order Actinomycetales, are fertile producers of bioactive secondary metabolites, including antibiotics. Nearly two-thirds of antibiotics that are used for the treatment of bacterial infections were originally isolated from actinomycetes strains belonging to the genus Streptomyces. This emphasizes the importance of actinomycetes in antibiotic discovery. However, the identification of a new antimicrobial compound and the exploration of its mode of action are very challenging tasks. Therefore, different approaches that enable the "detection" of an antibiotic and the characterization of the mechanisms leading to the biological activity are indispensable. Beyond bioinformatics tools facilitating the identification of biosynthetic gene clusters (BGCs), whole cell-screenings-in which cells are exposed to actinomycete-derived compounds-are a common strategy applied at the very early stage in antibiotic drug development. More recently, target-based approaches have been established. In this case, the drug candidates were tested for interactions with usually validated targets. This review focuses on the bioactivity-based screening methods and provides the readers with an overview on the most relevant assays for the identification of antibiotic activity and investigation of mechanisms of action. Moreover, the article includes examples of the successful application of these methods and suggestions for improvement.

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.

Marine Pharmacology in 2016-2017: Marine Compounds with Antibacterial, Antidiabetic, Antifungal, Anti-Inflammatory, Antiprotozoal, Antituberculosis and Antiviral Activities; Affecting the Immune and Nervous Systems, and Other Miscellaneous Mechanisms of Action

The review of the 2016-2017 marine pharmacology literature was prepared in a manner similar as the 10 prior reviews of this series. Preclinical marine pharmacology research during 2016-2017 assessed 313 marine compounds with novel pharmacology reported by a growing number of investigators from 54 countries. The peer-reviewed literature reported antibacterial, antifungal, antiprotozoal, antituberculosis, and antiviral activities for 123 marine natural products, 111 marine compounds with antidiabetic and anti-inflammatory activities as well as affecting the immune and nervous system, while in contrast 79 marine compounds displayed miscellaneous mechanisms of action which upon further investigation may contribute to several pharmacological classes. Therefore, in 2016-2017, the preclinical marine natural product pharmacology pipeline generated both novel pharmacology as well as potentially new lead compounds for the growing clinical marine pharmaceutical pipeline, and thus sustained with its contributions the global research for novel and effective therapeutic strategies for multiple disease categories.

Adding value to home compost: Biopesticide properties through Bacillus thuringiensis inoculation

Home and community composting are considered potential tools for the self-management of organic waste. The production of added value products from biowaste is an encouraging step further to valorise this waste stream. To increase the profits of homemade compost, this paper presents a strategy to produce enriched home compost with biopesticide properties through a simple and low-cost process. Bacillus thuringiensis (Bt) was inoculated in a home composter bin through a solid inoculum previously prepared using the same waste as substrate. The process was monitored and compared with a home composting control process without inoculation. Final composts were analysed and compared in terms of physicochemical and microbiological properties, respiration and germination indices, indicating the suitability of both to be used as organic amendments. Also, a standardized toxicity test proved that Bt-enriched compost can be safely applied to the soil. Microbiological analysis revealed highly diverse communities in both cases, with limited differences at phylum taxonomic level, but dissimilar relative abundances of species within phylum. Bacteroidetes and Proteobacteria were dominant, with the presence of species able to transform organic matter from vegetal origin, but not usually related to compost. Bt-cristal toxin was clearly present in Bt-enriched compost, indicating the coexistence of Bt with the different microbial populations till the end of the composting process. Although Bt has been widely investigated due to its biopesticide properties, the incorporation of this microorganism to home composting level has not been previously reported.

Antarctic Streptomyces fildesensis So13.3 strain as a promising source for antimicrobials discovery

Antarctic have been suggested as an attractive source for antibiotics discovery and members of Streptomyces genus have historically been studied as natural producers of antimicrobial metabolites. Nonetheless, our knowledge on antibiotic-producing Streptomyces from Antarctic is very limited. In this study, the antimicrobial activity of organic extracts from Antarctic Streptomyces strains was evaluated by disk diffusion assays and minimum inhibitory concentration. The strain Streptomyces sp. So13.3 showed the greatest antibiotic activity (MIC = 15.6 μg/mL) against Gram-positive bacteria and growth reduction of Gram‒negative pathogens. The bioactive fraction in the crude extract was revealed by TLC‒bioautography at R_f = 0.78 with molecular weight between 148 and 624 m/z detected by LC-ESI-MS/MS. The strain So13.3 was taxonomically affiliated as Streptomyces fildesensis. Whole genome sequencing and analysis suggested a 9.47 Mb genome size with 42 predicted biosynthetic gene clusters (BGCs) and 56 putative clusters representing a 22% of total genome content. Interestingly, a large number of them (11 of 42 BGCs and 40 of 56 putative BGCs), did not show similarities with other known BGCs. Our results highlight the potential of the Antarctic Streptomyces strains as a promising source of novel antimicrobials, particularly the strain Streptomyces fildesensis So13.3, which first draft genome is reported in this work.