Antibacterial Secondary Metabolites Research Articles

Phytochemical characterisation of dichloromethane and methanolic extracts of the Ziziphora tenuior leaves and evaluation of their antioxidant and antibacterial activities

Medicinal plants, known for their antibacterial phytocompounds and secondary metabolites, offer promising potential in combating antibiotic-resistant bacteria. This study aimed to perform a phytochemical analysis of the methanol and dichloromethane extracts obtained from Ziziphora tenuior leaves using GC-MS. Furthermore, the antioxidant activity of the extracts was evaluated through the DPPH assay. And, their antibacterial activity was assessed against S. aureus, E. coli, methicillin-resistant S. aureus, and vancomycin-resistant enterococcus (VRE) bacterial strains. Based on the results 90-92% of these extracts consisted of phytocompounds with pharmaceutical properties. Of these, 5-methyl- 2-(1-methylethylidele), Cyclohexanone (Pulegone; C10H16O) comprised the highest percentage of the extracts, constituting 62% of methanolic extract and 81% of dichloromethane extract. Also, both methanolic and dichloromethane extracts showed potent antioxidant activity with IC50 of 277.6 µg/ml and 49.6 µg/ml, respectively. Moreover, these extracts demonstrated considerable antibacterial activity against the tested pathogens, especially against S. aureus and VRE.

Preliminary Screening on Antibacterial Crude Secondary Metabolites Extracted from Bacterial Symbionts and Identification of Functional Bioactive Compounds by FTIR, HPLC and Gas Chromatography-Mass Spectrometry.

Secondary metabolites, bioactive compounds produced by living organisms, can unveil symbiotic relationships in nature. In this study, soilborne entomopathogenic nematodes associated with symbiotic bacteria (Xenorhabdus stockiae and Photorhabdus luminescens) were extracted from solvent supernatant containing secondary metabolites, demonstrating significant inhibitory effects against E. coli, S. aureus, B. subtilus, P. mirabilis, E. faecalis, and P. stutzeri. The characterization of these secondary metabolites by Fourier transforms infrared spectroscopy revealed amine groups of proteins, hydroxyl and carboxyl groups of polyphenols, hydroxyl groups of polysaccharides, and carboxyl groups of organic acids. Furthermore, the obtained crude extracts were analyzed by high-performance liquid chromatography for the basic identification of potential bioactive peptides. Gas chromatography-mass spectrometry analysis of ethyl acetate extracts from Xenorhabdus stockiae identified major compounds including nonanoic acid derivatives, proline, paromycin, octodecanal derivatives, trioxa-5-aza-1-silabicyclo, 4-octadecenal, methyl ester, oleic acid, and 1,2-benzenedicarboxylicacid. Additional extraction from Photorhabdus luminescens yielded functional compounds such as indole-3-acetic acid, phthalic acid, 1-tetradecanol, nemorosonol, 1-eicosanol, and unsaturated fatty acids. These findings support the potential development of novel natural antimicrobial agents for future pathogen suppression.

Novel Compounds Design of Acertannin, Hamamelitannin, and Petunidin-3-Glucoside Typical Compounds of African Leaves (Vernonia amygdalina Del) as Antibacterial Based on QSAR and Molecular Docking

Antibacterial secondary metabolites such as tannins and their derivatives are found in the Vernonia amygdalina Del. Antibiotic resistance can develop due to overuse, reducing the efficacy of drugs to prevent and treat infections. This research aims to use the Quantitative Structure-Activity Relationship (QSAR) and the semi-empirical method Austin Model 1 (AM1) to design a modified novel compound from African leaves that has improved antibacterial activity. This research includes a descriptor calculation of QSAR using AM1 MOE on typical compounds from African leaves, and calculation results are chosen based on a multilinear regression statistical analysis. The model equation represents the three primary parameters of QSAR, which are electronic, hydrophobic, and steric parameters, which will be used to measure modified compounds. Molecular docking using Autodock Tools (The Scripps Research Institute, USA), and analysis of results of docking Autodock Tools using Discovery Studio 3.5 Client. The best QSAR model obtained is LogEC50 = (0.829 x LogP) - (1,302 x AM1_HOMO) - (0.339 x AM1_dipole) - (5,128 x mr) + (0.145 x vol) - (11,355). The results showed that EC50 prediction of modified hamamelitannin has the best activity with the lowest ΔGbind -9.0 kcal/mol and inhibition constant of 0.249 μM. In summary, the novel compound's design calculation has better antibacterial activity, as indicated by a lower EC50, than fosfomycin or compounds without modification. The modified hamamelitannin compound was found to have better antibacterial activity (prediction EC50 = 0.1933 μM) than the original (experimental EC50 = 145.50 μM).

Impact of Cocoa Seed Extract Toothpaste on Plaque Reduction in Pediatric Populations

Plaque is a soft deposit that forms a helical biofilm layer and attached tightly to the tooth surface, in which its presence requiring the use of specific control agents. The safest and most effective plaque control is to use a toothbrush and toothpaste. On the other hand, extract from Theobroma cacao L. seeds contains antioxidant and antibacterial secondary metabolites which could act as a toothpaste active agent. The aim of this research was to determine the impact of Theobroma cacao L. seeds-added toothpaste in reducing plaque index of among children. This is a non-blinding clinical experiment with a pre-test and post-test research design. The research subjects were 30 healthy children aged 8-10 years which were randomly divided into three arms (treatment and control). The results revealed that Theobroma cacao L. extract used as the active ingredient contained contains phenolics, tannins, flavonoids, terpenoids, saponins, and alkaloids. Significantly higher plaque index reductions were observed among children treated with toothpaste containing 1% (mean difference=2.060; p=0.06) as compared to control. In conclusion, the Theobroma cacao L. seeds-added toothpaste could significantly reduce plaque index among healthy children.

Variation of antibacterial and antioxidant secondary metabolites and volatiles in leaf and callus extracts of Phulai (Acacia Modesta Wall.)

BackgroundAcacia species are economically significant as medicinal plants that have been utilized since ancient times. Acacia modesta has been reported to possess potent antibacterial and antioxidant properties, but its growth rate is slow. In this study, we hypothesized that inducing callus in vitro from A. modesta could enhance the production of antibacterial and antioxidant secondary metabolites, thereby circumventing the issues of slow growth and excessive harvesting of the plant.ResultsThe callus was induced from axillary buds on MS medium supplemented with 1 mg/L of 2,4-D and 1 mg/L of BAP. The secondary metabolites, volatile compounds, antibacterial activity, and antioxidant activity of the callus and parent plant leaf extracts were evaluated. The results revealed that the content of phenolics and flavonoids, the number of volatile compounds, and the antibacterial and antioxidant activities of the callus extract were significantly enhanced (P ≤ 0.05) compared to the leaf extract. The antibacterial and antioxidant effects were strongly correlated with the total phenolic and flavonoid content in the extracts.ConclusionsOur findings suggest that in vitro callus culture increases the production of phenolics, flavonoids, and volatile compounds. This subsequently enhances the antibacterial and antioxidant properties of A. modesta.

Bioprospecting of Actinobacterial Diversity and Antibacterial Secondary Metabolites from the Sediments of Four Saline Lakes on the Northern Tibetan Plateau.

The Tibetan Plateau, known as the "Roof of the World" and "The Third Pole", harbors numerous saline lakes primarily distributed in the Northern Tibetan Plateau. However, the challenging conditions of high altitude, low oxygen level, and harsh climate have limited investigations into the actinobacteria from these saline lakes. This study focuses on investigating the biodiversity and bioactive secondary metabolites of cultivable actinobacteria isolated from the sediments of four saline lakes on the Northern Tibetan Plateau. A total of 255 actinobacterial strains affiliated with 21 genera in 12 families of 7 orders were recovered by using the pure culture technique and 16S rRNA gene phylogenetic analysis. To facilitate a high-throughput bioactivity evaluation, 192 isolates underwent OSMAC cultivation in a miniaturized 24-well microbioreactor system (MATRIX cultivation). The antibacterial activity of crude extracts was then evaluated in a 96-well plate antibacterial assay. Forty-six strains demonstrated antagonistic effects against at least one tested pathogen, and their underlying antibacterial mechanisms were further investigated through a dual-fluorescent reporter assay (pDualrep2). Two Streptomyces strains (378 and 549) that produce compounds triggering DNA damage were prioritized for subsequent chemical investigations. Metabolomics profiling involving HPLC-UV/vis, UPLC-QTOF-MS/MS, and molecular networking identified three types of bioactive metabolites belonging to the aromatic polyketide family, i.e., cosmomycin, kidamycin, and hedamycin. In-depth analysis of the metabolomic data unveiled some potentially novel anthracycline compounds. A genome mining study based on the whole-genome sequences of strains 378 and 549 identified gene clusters potentially responsible for cosmomycin and kidamycin biosynthesis. This work highlights the effectiveness of combining metabolomic and genomic approaches to rapidly identify bioactive chemicals within microbial extracts. The saline lakes on the Northern Tibetan Plateau present prospective sources for discovering novel actinobacteria and biologically active compounds.

In silico and in vitro safety assessment of a fungal biomass from Rhizomucor pusillus for use as a novel food ingredient.

To address the growing world population and reduce the impact of environmental changes on the global food supply, ingredients are being produced using microorganisms to yield sustainable and innovative products. Food ingredients manufactured using modern biotechnology must be produced by non-toxigenic and nonpathogenic production organisms that do not harbor antimicrobial resistance (AMR). Several fungal species represent attractive targets as sources of alternative food products. One such product is a fungal biomass obtained from the fermentation of Rhizomucor pusillus strain CBS 143028. The whole genome sequence of this strain was annotated and subjected to sequence homology searches and in silico phenotype prediction tools to identify genetic elements encoding for protein toxins active via oral consumption, virulence factors associated with pathogenicity, and determinants of AMR. The in silico investigation revealed no genetic elements sharing significant sequence homology with putative virulence factors, protein toxins, or AMR determinants, including the absence of mucoricin, an essential toxin in the pathogenesis of mucormycosis. These in silico findings were corroborated in vitro based on the absence of clinically relevant mycotoxin or antibacterial secondary metabolites. Consequently, it is unlikely that R. pusillis strain CBS 143028 would pose a safety concern for use in food for human consumption.

Methanolic Extract Of Swietenia macrophylla Exhibits Antibacterial And Antibiofilm Efficacy Against Gram-Positive Pathogens

Gram-positive pathogens cause infections such as pneumonia, skin infections, anthrax, and sinusitis. The objective of this study was to determine the phytochemical profile, antibacterial and antibiofilm efficacy of Swietenia macrophylla methanolic extract (SMME) against Gram-positive pathogens. The secondary metabolites of SMME were analyzed using GC-MS while the antibacterial efficacy of SMME against Staphylococcus aureus ATCC 33862, Bacillus cereus ATCC 11778, Streptococcus pneumonia ATCC 19615, and Clostridium sporogenes ATCC 13124 was assessed using MIC and MBC assays. Biofilm biomass assay and time-kill assay were performed to determine the antibiofilm activity of SMME against the pathogens. Results demonstrated that six common antibacterial secondary metabolites were present in the SMME. The major compound was found to be β-amyrin (22.8%). The SMME showed the lowest MIC values against B. cereus (31.25 µg/mL) and C. sporogenes (31.25 µg/mL) and the lowest MBC value against S. aureus (1000 µg/mL). The SMME also significantly (p<0.05) inhibited all the biofilms. It started to inhibit S. pneumonia and C. sporogenes biofilms after 12 h of exposure. On the other hand, the BIC50 value showed that the SMME was most effective against B. cereus. In conclusion, the secondary metabolites in the SMME may contribute to the antibacterial and antibiofilm efficacy against Gram-positive pathogens.

Uji Aktivitas Antibakteri Ekstrak Etanol Daun Matoa (Pometia Pinnata J. R & G.Forst.) terhadap Pertumbuhan Staphylococcus Aureus dan Escherichia Coli

This study aims to determine the antibacterial activity, effective concentration, and secondary metabolites in the ethanol extract of matoa left against the test bacteria Staphylococcus aureus and Escherichia coli. The research method extracts matoa leaf samples by maceration using 70% ethanol solvent, testing the antibacterial activity using the paper disk diffusion method. The results of the antibacterial activity test were then analyzed using the One way ANOVA method. The results showed that the diameter of the inhibition zone of the ethanol extract of matoa leaves on the growth of Staphylococcus aureus appeared to have a clear area at a concentration of 1%, 1.5%, and 2%, respectively, of 12.88 mm, 13.15 mm, 11.36 mm. In comparison, the results of measuring the diameter of the inhibition zone of the ethanol extract matoa leaf on the growth of Escherichia coli bacteria were seen to have a clear area at a concentration of 1%, 1.5%, and 2% of 9.5 mm, 10.23 mm, 12.1 mm respectively. This activity is thought to be due to the effects of alkaloid compounds, flavonoids, tannins, saponins, and steroids in the ethanol extract of matoa leaves. Based on the ANOVA test, a significance value of 0.000 <0.05 was obtained, so the results were significant. In conclusion, there are substantial differences in the use of various concentrations of matoa leaf extract on the growth of Staphylococcus aureus and Escherichia coli bacteria.
 Keywords: Antibacterial Activity, Matoa Leaves, Secondary Metabolites

Optimization of cultural conditions for biomass and antibacterial metabolite production by Aspergillus fumigatus strain MF1

The interest of this work is to study the optimized conditions for antibacterial secondary metabolites from the fungus Aspergillus fumigatus strain MF1 extract. The secondary metabolites such as alkaloids, phenols, terpenoids, toxins and ketones are fascinating in the growth of antimicrobial performance of derived compound from strain MF1 extract in addition to the production of biomass. Hence, there is a need to optimize the conditions like temperature, salt concentration, radiation and pH of culture media to enhance the production of biomass and antibacterial metabolite. However, in this study, the authors examined the antibacterial performance of eight bacterial isolates and results showed that Potato dextrose broth (PDB) for seven days incubation at 30 ​°C temperature, pH-6, maltose (carbon source), yeast extract (nitrogen source), and 5% NaCl is the optimized parameters for high yielding of biomass and antibacterial secondary metabolites by A. fumigatus MF1 extract.

Antibacterial and cytotoxic secondary metabolites from endophytic fungi associated with Antidesma bunius leaves

In vitro \a-glucosidase inhibition and antioxidant activities of partially purified Antidesma bunius fruit and Gynura nepalensis leaf extractsNoel Quiming, Joannes Luke Asis, Marilou Nicolas, Dhennis Versoza, Michael Russelle Alvarez

UV-mediated enhancement of antibacterial secondary metabolites in endophytic Lasiodiplodia theobromae

In the science of drug discovery, ultraviolet (UV) irradiation has been applied to induce mutagenesis in fungi to provide possibilities for the stimulation or enhancement of fungal biosynthetic capabilities. This study was carried out to evaluate the effect of UV radiation on the biosynthesis of antibacterial secondary metabolites in an endophytic Lasiodiplodia theobromae. Using standard methods, the fungus was isolated from healthy leaves of Cola acuminata and identified based on PCR amplification and genomic sequencing of the internal transcribed spacer (ITS) region. Cultures of L. theobromae were exposed to UV radiation at different time intervals of 1, 2 and 5 min. The fungus was subjected to solid-state fermentation in rice medium before and after UV treatments. The fungal secondary metabolites were extracted and tested for antibacterial activity using the agar diffusion method. Compounds present in the obtained extracts were identified by HPLC and GC-MS analysis. At a concentration of 1 mg/ml, the extract of the wild type L. theobromae (untreated) was observed to only inhibit Staphylococcus aureus, with an IZD of 12 mm. However, the extract of UV-treated L. theobromae (2 min) inhibited S. aureus, Escherichia coli and Pseudomonas aeruginosa with an IZD of 10 and 4 mm respectively. A wide array of compounds in the phenolics, fatty acids, alkaloids and alkanes classes were identified in the UV-treated and untreated fungal extracts. Overall, UV treatments of L. theobromae stimulated the production of seventeen (17) new compounds that were not detected in the untreated strain. The study confirms UV irradiation as an effective method for stimulating microbial biosynthesis of new bioactive compounds, indicating a promising and potentially abundant source of new drug compounds from microorganisms.

Polarity-guided phytochemical extraction, polyphenolic characterization, and multimode biological evaluation of Seriphidium kurramense (Qazilb.) Y. R. Ling

The undertaken study aims to assess the polyphenolic profile, and antioxidant, antimicrobial, antiviral, antidiabetic, and cytotoxic potential of Seriphidium kurramense (Qazilb.) Y. R. Ling extracts. Extracts of aerial parts were prepared by successive extraction (n-hexane {Sk-nH}, ethyl acetate {Sk-EA}, methanol {Sk-M} and aqueous {Sk-Aq}). Chromogenic assays determined the antioxidant profile while HPLC quantified several polyphenols. Agar well diffusion was employed for antimicrobial potential while brine shrimp and hemolytic assays established the biosafety profile. The results have shown that maximum extract recovery (17.49% w/w), total phenolics content (24.44 ± 0.15 μg GAE/mgE), and total flavonoids content (6.87 ± 0.25 μg QE/mgE) were recorded in Sk-Aq. RP-HPLC quantified a significant amount of syringic acid (1.43 ± 0.05 µg/mgE), caffeic acid (0.48 ± 0.02 µg/mgE), gentisic acid (6.44 ± 0.01 µg/mgE), and quercetin (4.39 ± 0.01 µg/mgE) in Sk-Aq, while maximum amounts of thymoquinone (0.21 ± 0.02 µg/mgE) and luteolin (3.90 ± 0.03 µg/mgE) along with apigenin (3.72 ± 0.03 µg/mgE) existed in Sk-M and highest quantities of ferulic acid (2.98 ± 0.01 µg/mgE), myricetin (1.04 ± 0.02 µg/mgE) and kaempferol (1.23 ± 0.01 µg/mgE) were found to be present in Sk-EA. A substantial free radical scavenging (85.87 ± 1.00%), total reducing power (211.93 ± 0.97 µg AAE/mgE), and urease inhibition activity (87.99 ± 0.19% at 500 µg/ml) were also recorded in the Sk-Aq. The highest antioxidant capacity (243.5 ± 1.12 µg AAE/mgE), antibacterial, antifungal, and antiviral activity (100% reduction in plaque formation at 400 µg/ml) were observed for Sk-EA. Maximum antibacterial and antifungal activities were revealed against Klebsiella pneumoniae (MIC = 25 ± 0.37 µg/ml), and Candida albicans (MIC = 50 ± 0.19 µg/ml) respectively. The prominent antidiabetic potential was displayed by Sk-nH in terms of α-amylase and α-glucosidase inhibition. The results reported, herein suggest that S. kurramense can be a promising candidate for antioxidant, antibacterial, antifungal, antiviral, and antidiabetic secondary metabolites.

Bioprospecting of actinomycetes for anti-bacterial potential: A Review

Actinomycetes are gram-positive bacteria that have a high GC content compared to their counterparts. Actinomycetes were capable of producing a broad range of secondary metabolites and many of these were anti-bacterial agents. Antibiotics have been known to play a vital role in therapeutics and the clinical management of various diseases. Actinomycetes have contributed more than 70% of known antibiotics in the market today. Apart from antibiotics, actinomycetes also produce several enzymes, enzyme inhibitors, anticancer and anti-diabetic secondary metabolites. Currently, actinomycetes are being studied for medicinal, pharmaceutical, industrial, environmental and bioremediation applications. The current study focuses on a variety of antibacterial agents derived from actinomycetes and new antibiotics under clinical trial along with their mode of action. It also describes the genome mining methods for screening actinomycetes isolates for biosynthetic gene clusters and specific antibacterial secondary metabolites.

Complete Genome Sequences of Five Gram-Negative Bacterial Strains Comprising Synthetic Bacterial Consortium "The Great Five" with Antagonistic Activity Against Plant-Pathogenic Pectobacterium spp. and Dickeya spp.

Complete Genome Sequences of Five Gram-Negative Bacterial Strains Comprising Synthetic Bacterial Consortium "The Great Five" with Antagonistic Activity Against Plant-Pathogenic Pectobacterium spp. and Dickeya spp.

Isolation and Characterization of Werneria Chromene and Dihydroxyacidissimol from Burkillanthus malaccensis (Ridl.) Swingle

The secondary metabolites of endemic plants from the Rutaceae family, such as Burkillanthus malaccensis (Ridl.) Swingle from the rainforest of Malaysia, has not been studied. Burkillanthus malaccensis (Ridl.) Swingle may produce antibacterial and antibiotic-potentiating secondary metabolites. Hexane, chloroform, and methanol extracts of leaves, bark, wood, pericarps, and endocarps were tested against bacteria by broth microdilution assay and their antibiotic-potentiating activities. Chromatographic separations of hexane extracts of seeds were conducted to investigate effective phytochemicals and their antibacterial activities. Molecular docking studies of werneria chromene and dihydroxyacidissiminol against SARS-CoV-2 virus infection were conducted using AutoDock Vina. The methanol extract of bark inhibited the growth of Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa with the minimum inhibitory concentration of 250, 500, and 250 µg/mL, respectively. The chloroform extract of endocarps potentiated the activity of imipenem against imipenem-resistant Acinetobacter baumannii. The hexane extract of seeds increased the sensitivity of P. aeruginosa against ciprofloxacin and levofloxacin. The hexane extract of seeds and chloroform extract of endocarps were chromatographed, yielding werneria chromene and dihydroxyacidissiminol. Werneria chromene was bacteriostatic for P. aeruginosa and P. putida, with MIC/MBC values of 1000 > 1000 µg/mL. Dihydroxyacidissiminol showed the predicted binding energies of −8.1, −7.6, −7.0, and −7.5 kcal/mol with cathepsin L, nsp13 helicase, SARS-CoV-2 main protease, and SARS-CoV-2 spike protein receptor-binding domain S-RBD. Burkillanthus malaccensis (Ridl.) Swingle can be a potential source of natural products with antibiotic-potentiating activity and that are anti-SARS-CoV-2.

Marine fungal metabolites as a source of drug leads against aquatic pathogens.

Aquatic pathogens, including Vibrio, Edwardsiella, Pseudomonas, and Aeromonas, which could result in bacterial diseases to aquaculture, have seriously threatened the world aquaculture production. Marine-derived fungi, which could produce novel secondary metabolites with significant antibacterial activity, may be an important source for finding effective agents against aquatic pathogens. In this review, a systematically overview of the harm of several aquatic pathogens, and 134 antibacterial secondary metabolites against aquatic pathogens from 13 genera of marine-derived fungi, were summarized and concluded. The aim of this review is to find out the relationships between activity and structural type, between bioactive compounds and their hosts, and so on. Altogether, 95 references published during 1997-2021 were cited. KEY POINTS: •Aquatic pathogens, which could result in bacterial diseases to aquaculture, were described. •Marine fungal metabolites with activities against aquatic pathogens were summarized. •The distributions of these bioactive marine fungal metabolites were analyzed.

New Antibacterial Secondary Metabolites from a Marine-Derived Talaromyces sp. Strain BTBU20213036.

New polyketide-derived oligophenalenone dimers, bacillisporins K and L (1 and 2) and xanthoradone dimer rugulosin D (3), together with four known compounds, bacillisporin B (4), macrosporusone D (5), rugulosin A and penicillide (6 and 7), were isolated from the marine-derived fungus Talaromyces sp. BTBU20213036. Their structures were determined by detailed analysis of HRESIMS, 1D and 2D NMR data, and the absolute configurations were determined on the basis of calculated and experimental electronic circular dichroism (ECD). The antibacterial and antifungal activities of these compounds were tested against Gram-positive—Staphylococcus aureus, Gram-negative—Escherichia coli, and fungal strain—Candida albicans. These compounds showed potential inhibitory effects against S. aureus with minimum inhibitory concentrations ranging from 0.195 to 100 µg/mL.

Antibacterial Screening and Analysis of Streptomyces coelicolor Secondary Metabolites

Aims: The widespread usage of commercially accessible antibacterial agents has resulted in the emergence of multidrug-resistant bacterial pathogens worldwide. Streptomycetes produce a variety of antibacterial secondary metabolites and the study, as a result, will look into the antibacterial potential of Streptomyces coelicolor against some pathogenic bacteria.
 Place and Duration of Study: The study was based at the department of Medical Microbiology, Science and Health research center, Faculty of science and health, Koya University. between April, 2019 and December, 2020.
 Methodology: The Streptomyces coelicolor strains in this study were verified phenotypically via tryptone soya agar in addition to their genotype using three different sets of primers. Afterwards, Thin Layer Chromatography (TLC) was utilised to purify actinorhodin from the crude extract of S. coelicolor secondary metabolites. The antibacterial activities of the actinorhodin and the crude extract have further been tested against standard strains of Staphylococcus aureus (ATCC 25923), Streptococcus pyogenes (ATCC 19165), Escherichia coli (ATCC 25218), and Salmonella typhi (ATCC 14028). Disc diffusion and minimum inhibitory concentration (MIC) techniques were both used to serve this purpose.
 Results: A significant activity of the organic solvent extract was observed against Staphylococcus aureus and Streptococcus pyogenes using the disc diffusion method with diameter zone inhibition of (9-20 mm) and (11-23 mm), respectively. Actinorhodin, on the other hand, showed a reasonable wider effect against them with diameter zone inhibition of (10-24 mm) against S. aureus and (10-27 mm) against S. pyogenes. Comparatively, the MIC test showed akin results by inhibiting S. aureus and S. pyogenes at a MIC value of 16 µg/ml using crude extract. Whereas actinorhodin expressed greater inhibitory activities against S. aureus, S. pyogenes and S. typhi with MICs of (8, 16 and 32 µg/ml), respectively.
 Conclusion: The capability of suggested actinorhodin from the L646 strain to inhibit Staphylococcus aureus and Streptococcus pyogenes growth with a MIC value of 8 g/ml was a remarkable finding obtained by studying Streptomyces coelicolor secondary metabolites.

Variability in antimicrobial chemical defenses in the Caribbean sponge Agelas tubulata: implications for disease resistance and resilience

Sponges in the genus Agelas produce a diversity of bromopyrrole alkaloid secondary metabolites, some of which are known to inhibit predators and pathogens. Selective pressures on sponges to produce chemical defenses vary in time and space, often resulting in differences in the production of secondary metabolites. To characterize intraspecific variation in these compounds, we generated metabolomic profiles of the Caribbean sponge A. tubulata across spatial gradients, including multiple sites in Belize and Grand Cayman, and depths ranging from 15 to 61 m in Grand Cayman. Samples were also analyzed from a reciprocal transplant experiment across shallow (22 m) to mesophotic (61 m) reefs. We found quantitative, but not qualitative, differences in metabolite profiles across sites and depths, with 9 metabolites contributing to that variation. In addition, transplanting sponges across depths resulted in significant changes in concentrations of the metabolite sceptrin. Sponge extracts exhibited antibacterial activity against a panel of marine and human pathogens. Multiple regression analyses showed that different metabolites were associated with antibacterial activity against different pathogens. The strongest compound-specific relationship was a negative effect of oroidin on the growth of Serratia marcescens, and purified oroidin was found to inhibit S. marcescens growth in a dose-dependent manner. Overall, A. tubulata exhibits intraspecific variability in the production of antibacterial secondary metabolites across sites and depths that signals selective responses to its environment. Given the current increase in sponge densities, and incidence of disease on coral reefs, these data have implications for disease resistance and resilience of sponges in the Anthropocene.