Antimicrobial and antioxidant activities of a new benzamide from endophyticStreptomycessp. YIM 67086

Multiomics analysis reveals the genetic and metabolic characteristics associated with the low prevalence of dental caries

Background

Despite poor oral hygiene, the Baiku Yao (BKY) ethnic group in China presents a low prevalence of dental caries, which may be related to genetic susceptibility. Due to strict intra-ethnic marriage rule, this ethnic has an advantage in studying the interaction between genetic factors and other regulatory factors related to dental caries.

Methods

Peripheral blood from a caries-free adult male was used for whole genome sequencing, and the BKY assembled genome was compared to the Han Chinese genome. Oral saliva samples were collected from 51 subjects for metabolomic and metagenomic analysis. Multiomics data were integrated for combined analysis using bioinformatics approaches.

Results

Comparative genomic analysis revealed the presence of structural variations in several genes associated with dental caries. Metabolomic and metagenomic sequencing demonstrated the caries-free group had significantly higher concentration of antimicrobials and higher abundance of core oral health-related microbiota. The functional analysis indicated that cationic antimicrobial peptide resistance and the lipopolysaccharide biosynthesis pathway were enriched in the caries-free group.

Conclusions

Our study provided new insights into the specific regulatory mechanisms that contribute to the low prevalence of dental caries in the specific population and may provide new evidence for the genetic diagnosis and control of dental caries.

In vitro antibacterial effects of combination of ciprofloxacin with compounds isolated from Streptomyces luteireticuli NIIST-D75

Three phenazines, 1-methoxyphenazine (1), methyl-6-methoxyphenazine-1-carboxylate (2), 1,6-dimethoxyphenazine (4), and a 2,3-dimethoxy benzamide (3) were isolated from the Streptomyces luteireticuli NIIST-D75, and the antibacterial effects of compounds 1-3, each in combination with ciprofloxacin, were investigated. The in vitro antibacterial activity was assessed by microdilution, checkerboard, and time-kill assay against Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, and Salmonella typhi. According to the checkerboard assay results, each combination of compounds 1, 2 and 3 with ciprofloxacin resulted in a significantly lower minimum inhibitory concentrations (MICs) of 0.02-1.37 µg ml-1, suggesting synergistic combinations by fractional inhibitory concentration index, and displayed bactericidal activity in time-kill kinetics within 48 h. SEM analysis was carried out to determine the changes in morphology in S. aureus and E. coli during treatment with individual combination of ciprofloxacin and compounds (1-3), which revealed drastic changes in the cells such as dent formation, biofilm disruption, cell bursting, and doughnut-like formation, change in surface morphology in S. aureus, and cell elongation, cell burst with ruptured cell, and change in surface morphology in E. coli. Hep G2 cell viability was not affected by the compounds (1-3) that were tested for cytotoxicity up to 250 µM.

A New Saharan Strain of Streptomyces sp. GSB-11 Produces Maculosin and N-acetyltyramine Active Against Multidrug-Resistant Pathogenic Bacteria

Multi-resistant bacterial pathogens are a major public health problem for treating nosocomial infections owing to their high resistance to antibiotics. The objective of this research was to characterize the bioactive molecules secreted by a novel moderately halophilic actinobacterium strain, designated GSB-11, exhibiting a strong antagonistic activity against several multidrug-resistant pathogenic bacteria. This potential strain was identified by phenotypic, genotypic (16S rRNA), and phylogenetic analyses. GSB-11 was related to "Streptomyces acrimycini" NBRC 12736 ^T with 99.59% similarity. Molecular screening by PCR assay demonstrated that the strain possesses two biosynthetic genes coding for NRPS and PKS-II. Two active compounds GSB11-6 and GSB11-7 were extracted from the cell-free culture supernatant of Bennett medium and purified using reversed-phase HPLC. According to spectrometric (mass spectrum) and spectroscopic (¹H NMR, ¹³C NMR, ¹H-¹H COSY, and ¹H-¹³C HMBC) spectra analyses, the compounds GSB11-6 and GSB11-7 were identified to be maculosin and N-acetyltyramine, respectively. Their minimum inhibitory concentrations (MIC) revealed interesting values against certain multidrug-resistant pathogenic bacteria. They were between 5 and 15 mg/mL for GSB11-6, 10 and 30 mg/mL for GSB11-7. To our best knowledge, this is the first study of these active substances isolated from "Streptomyces acrimycini" showing an interesting antibacterial activity. Therefore, these essential compounds could be candidates for future research against multidrug-resistant bacteria.

A novel aureothin diepoxide derivative from Streptomyces sp. NIIST-D31 strain

A novel vicinal diepoxide of alloaureothin was isolated from Streptomyces sp. NIIST-D31 strain along with three carboxamides, p-aminobenzoic acid and 1,6-dimethoxyphenazine. Exhaustive 2D NMR analysis and analysis of experimental, theoretical CD spectra aided in establishing the structure of compound 1. Compound 1 inhibits adipogenesis and accumulation of lipid droplets during the differentiation of 3T3-L1 cells.

Microbial Metabolites Beneficial to Plant Hosts Across Ecosystems

Plants are intimately connected with their associated microorganisms. Chemical interactions via natural products between plants and their microbial symbionts form an important aspect in host health and development, both in aquatic and terrestrial ecosystems. These interactions range from negative to beneficial for microbial symbionts as well as their hosts. Symbiotic microbes synchronize their metabolism with their hosts, thus suggesting a possible coevolution among them. Metabolites, synthesized from plants and microbes due to their association and coaction, supplement the already present metabolites, thus promoting plant growth, maintaining physiological status, and countering various biotic and abiotic stress factors. However, environmental changes, such as pollution and temperature variations, as well as anthropogenic-induced monoculture settings, have a significant influence on plant-associated microbial community and its interaction with the host. In this review, we put the prominent microbial metabolites participating in plant-microbe interactions in the natural terrestrial and aquatic ecosystems in a single perspective and have discussed commonalities and differences in these interactions for adaptation to surrounding environment and how environmental changes can alter the same. We also present the status and further possibilities of employing chemical interactions for environment remediation. Our review thus underlines the importance of ecosystem-driven functional adaptations of plant-microbe interactions in natural and anthropogenically influenced ecosystems and their possible applications.

A Review on Microbial Products and Their Perspective Application as Antimicrobial Agents

Microorganisms including actinomycetes, archaea, bacteria, fungi, yeast, and microalgae are an auspicious source of vital bioactive compounds. In this review, the existing research regarding antimicrobial molecules from microorganisms is summarized. The potential antimicrobial compounds from actinomycetes, particularly Streptomyces spp.; archaea; fungi including endophytic, filamentous, and marine-derived fungi, mushroom; and microalgae are briefly described. Furthermore, this review briefly summarizes bacteriocins, halocins, sulfolobicin, etc., that target multiple-drug resistant pathogens and considers next-generation antibiotics. This review highlights the possibility of using microorganisms as an antimicrobial resource for biotechnological, nutraceutical, and pharmaceutical applications. However, more investigations are required to isolate, separate, purify, and characterize these bioactive compounds and transfer these primary drugs into clinically approved antibiotics.

Spectral analysis and detailed quantum mechanical investigation of some acetanilide analogues and their self-assemblies with graphene and fullerene

Spectroscopic analysis and different quantum mechanical studies of four pharmaceutically active compounds phenacetin, p-acetanisidide, 4'-butoxyacetanilide, and 4'-(3-chloropropoxy)acetanilide are reported in this manuscript. Simulated IR spectrum of these compounds was compared with experimentally available data, and essential functional group assignments were made. We also report the frontier orbital properties and other derived local energy descriptors which talks about the relative stability and reactivity. Photovoltaic efficiency of the compounds was studied from the simulated electronic spectra. The compound was found to interact with graphene and fullerene, to form molecular self-assembly. These self-assemblies showed tremendous enhancement in various physicochemical properties when compared with its constituents. The nature of the interactions between studied chemical species was discussed with the help of chemical reactivity principles. Biological activity of the compounds was predicted using molecular docking studies. It is interesting to see that on adsorption with a graphene/fullerene surface, all adsorbed complex shows enhancement in the Raman activity giving surface enhanced Raman spectra (SERS). This can be used for the detection of these drugs in a pharmacological or biological sample. Interestingly the graphene/fullerene drug molecular assembly shows enhanced biological activity when compared with individual drug molecules. Graphical abstract.

Streptomyces-Derived Metabolites with Potential Photoprotective Properties-A Systematic Literature Review and Meta-Analysis on the Reported Chemodiversity

Sun overexposure is associated with the development of diseases that primarily affect the skin, which can lead to skin cancer. Among the main measures of photoprotection is the use of sunscreens. However, there is currently concern about the reported harmful effects to both humans and the environment due to several of the sunscreen ingredients available on the market. For this reason, the search for and development of new agents with photoprotective properties is required. In searching for these metabolites, researchers have turned their attention to microbial sources, especially the microbiota in unusual hostile environments. Among the diverse microorganisms available in nature, Actinobacteria and specifically Streptomyces, have been shown to be a source of metabolites with various biological activities of interest, such as antimicrobial, antitumor and immunomodulator activities. Herein, we present the results of a systematic review of the literature in which Streptomyces isolates were studied as a source of compounds with photoprotective properties. A meta-analysis of the structure-property and structure-activity relationships of those metabolites identified in the qualitative analysis phase was also carried out. These findings indicate that Streptomyces are a source of metabolites with potential applications in the development of new, safe and more eco-friendly sunscreens.

Efficacy of metabolites of a Streptomyces strain (AS1) to control growth and mycotoxin production by Penicillium verrucosum, Fusarium verticillioides and Aspergillus fumigatus in culture

The objectives of this study were to determine the efficacy of metabolites of a Streptomyces strain AS1 on (a) spore germination, (b) mycelial growth, (c) control of mycotoxins produced by Penicillium verrucosum (ochratoxin A, OTA), Fusarium verticillioides (fumonisins, FUMs) and Aspergillus fumigatus (gliotoxin) and (d) identify the predominant metabolites involved in control. Initial screening showed that the Streptomyces AS1 strain was able to inhibit the mycelial growth of the three species at a distance, due to the release of secondary metabolites. A macroscopic screening system showed that the overall Index of Dominance against all three toxigenic fungi was inhibition at a distance. Subsequent studies showed that the metabolite mixture from the Streptomyces AS1 strain was very effective at inhibiting conidial germination of P. verrucosum, but less so against conidia of A. fumigatus and F. verticillioides. The efficacy was confirmed in studies on a conducive semi-solid YES medium in BioScreen C assays. Using the BioScreen C and the criteria of Time to Detection (TTD) at an OD = 0.1 showed good efficacy against P. verrucosum when treated with the Streptomyces AS1 extract at 0.95 and 0.99 water activity (a_w) when compared to the other two species tested, indicating good efficacy. The effective dose for 50% control of growth (ED₅₀) at 0.95 and 0.99 a_w were approx. 0.005 ng/ml and 0.15 μg/ml, respectively, with the minimum inhibitory concentration (MIC) at both a_w levels requiring > 40 μg/ml. In addition, OTA production was completely inhibited by 2.5 μg/ml AS1 extract at both a_w levels in the in vitro assays. Ten metabolites were identified with four of these being predominant in concentrations > 2 μg/g dry weight biomass. These were identified as valinomycin, cyclo(L-Pro-L-Tyr), cyclo(L-Pro-L-Val) and brevianamide F.

Investigating the Role of Endophytic Fungi in Gentiana scabra bge. by Cross-Growth Period Inoculation

Gentiana scabra Bge. (gentian) is a Chinese medicinal plant. Endophytic fungi from the roots of gentian were isolated and cross-growth period inoculation was performed to study the roles of three Trichoderma spp. strains (F1, F2, and F9) in their original host plant. In treatments inoculated with F1, F2, and F9, gentiopicroside content increased 33.6, 23.7 and 13% than that in the control. Strains F1, F2, and F9 could also improve polysaccharide content by more than 6.6, 18.7 and 30% compared to the control. The incidence of spot blight in gentian inoculated with F1, F2, and F9 decreased by 31.2, 26.7 and 8.5%. Inconsistent changes in the activity of the three enzymes (superoxide dismutase, catalase and peroxidase) were observed when the plants were attacked by pathogens or inoculated with fungi. High enzymatic activity did not reflect mild disease. Cross-growth period inoculation, which takes into account the original living environment (gentian plant as "substrate" and different microorganisms as symbionts) of endophytic fungi, provides a new idea for studying effects of endophytes on their original hosts. This is the first research about the role of endophytic fungi in Gentiana scabra bge. in vivo.

New pyrazinoquinazoline alkaloids Isolated from a culture of Stenotrophomonas maltophilia QB-77

Two new pyrazinoquinazoline alkaloids, epi-fiscalin D (1) and epi-fiscalin E (2), as well as three known analogues, norquinadoline A (3), quinadoline A (4), and fiscalin C (5), were isolated from ethyl acetate extract of the fermentation broth of Stentrophomonas maltophilia QB-77. The structures of new compounds were elucidated on the basis of extensive spectroscopic data analysis including UV, HRESIMS, and 1D and 2D NMR experiments. All the isolated compounds were tested for their in vitro cytotoxicity against five human cancer cell lines (SMMC-7721, MCF-7, HL-60, SW480, and A-549) and antibacterial activities against Bacillus subtilis, Escherichia coli, and Staphylococcus aureus.

Streptomyces ginkgonis sp. nov., an endophyte from Ginkgo biloba

A novel endophytic actinomycete strain, designated KM-1-2^T, was isolated from seeds of Ginkgo biloba at Yangling, China. A polyphasic approach was used to study the taxonomy of strain KM-1-2^T and it was found to show a range of phylogenetic and chemotaxonomic properties consistent with those of members of the genus Streptomyces. The diamino acid of the cell wall peptidoglycan was identified as LL-diaminopimelic acid. No diagnostic sugars were detected in whole cell hydrolysates. The predominant menaquinones were identified as MK-9(H₆) and MK-9(H₈). The diagnostic phospholipids were found to be phosphatidylethanolamine and phosphatidylcholine. The DNA G + C content of the novel strain was determined to be 72.9 mol%. The predominant cellular fatty acids (> 10.0 %) were identified as iso-C_14 : 0, iso-C_16 : 0, C_16 : 0 and C_17 : 0 cyclo. Phylogenetic analysis based on the 16S rRNA gene sequence revealed that the strain is closely related to Streptomyces carpaticus JCM 6915^T (99.3%), Streptomyces harbinensis DSM 42076^T (98.9%) and Streptomyces cheonanensis JCM 14549^T (98.5%). DNA-DNA hybridizations with these three close relatives gave similarity values of 39.1 ± 1.9, 35.8 ± 2.3, and 47.4 ± 2.7%, respectively, which indicated that strain KM-1-2^T represents a novel species of the genus Streptomyces. This is consistent with the morphological, physiological and chemotaxonomic data. Cumulatively, these data suggest that strain KM-1-2^T represents a novel Streptomyces species, for which the name Streptomyces ginkgonis sp. nov. is proposed, with the type strain KM-1-2^T (= CCTCC AA2016004^T = KCTC 39801^T).

Endophytic actinobacteria: Diversity, secondary metabolism and mechanisms to unsilence biosynthetic gene clusters

Endophytic actinobacteria, which reside in the inner tissues of host plants, are gaining serious attention due to their capacity to produce a plethora of secondary metabolites (e.g. antibiotics) possessing a wide variety of biological activity with diverse functions. This review encompasses the recent reports on endophytic actinobacterial species diversity, in planta habitats and mechanisms underlying their mode of entry into plants. Besides, their metabolic potential, novel bioactive compounds they produce and mechanisms to unravel their hidden metabolic repertoire by activation of cryptic or silent biosynthetic gene clusters (BGCs) for eliciting novel secondary metabolite production are discussed. The study also reviews the classical conservative techniques (chemical/biological/physical elicitation, co-culturing) as well as modern microbiology tools (e.g. next generation sequencing) that are being gainfully employed to uncover the vast hidden scaffolds for novel secondary metabolites produced by these endophytes, which would subsequently herald a revolution in drug engineering. The potential role of these endophytes in the agro-environment as promising biological candidates for inhibition of phytopathogens and the way forward to thoroughly exploit this unique microbial community by inducing expression of cryptic BGCs for encoding unseen products with novel therapeutic properties are also discussed.

A new bioactive diterpenoid from pestalotiopsis adusta, an endophytic fungus from clerodendrum canescens

Bioassay-guided fractionation of the culture extract of Pestalotiopsis adusta, an endophytic fungus isolated from the medicinal plant Clerodendrum canescens, led to the isolation of one new, (10S)-12,16-epoxy-17(15→16)-abeo-3,5,8,12,15-abietapentaen-2,7,11,14-tetraone (1), and four known diterpenoids, teuvincenone F (2), uncinatone (3), coleon U (4), coleon U-12-methyl ether (5). These structures were identified by using spectroscopic methods, including UV, MS, 1D and 2D NMR experiments. This is the first report of these compounds being isolated from a Pestalotiopsis species. The cytotoxic activities of the compounds were evaluated, and compounds 1 and 3 demonstrated cytotoxic activities against the HL-60 tumour cell line (IC₅₀ ＜ 20 μM).

Continuing hunt for endophytic actinomycetes as a source of novel biologically active metabolites

Drug-resistant pathogens and persistent agrochemicals mount the detrimental threats against human health and welfare. Exploitation of beneficial microorganisms and their metabolic inventions is most promising way to tackle these two problems. Since the successive discoveries of penicillin and streptomycin in 1940s, numerous biologically active metabolites have been discovered from different microorganisms, especially actinomycetes. In recent years, actinomycetes that inhabit unexplored environments have received significant attention due to their broad diversity and distinctive metabolic potential with medical, agricultural and industrial importance. In this scenario, endophytic actinomycetes that inhabit living tissues of plants are emerging as a potential source of novel bioactive compounds for the discovery of drug leads. Also, endophytic actinomycetes are considered as bio-inoculants to improve crop performance through organic farming practices. Further efforts on exploring the endophytic actinomycetes associated with the plants warrant the likelihood of discovering new taxa and their metabolites with novel chemical structures and biotechnological importance. This mini-review highlights the recent achievements in isolation of endophytic actinomycetes and an assortment of bioactive compounds.