Microbicidal and anti-inflammatory effects of Actinomadura spadix (EHA-2) active metabolites from Himalayan soils, India

Streptomyces virginiae XDS1-5, an antagonistic actinomycete, as a biocontrol to peach brown rot caused by Monilinia fructicola

BACKGROUND

Peach brown rot, caused by the pathogen Monilinia fructicola, represents a significant postharvest infectious disease affecting peach fruit. This disease is responsible for a substantial increase in fruit decay rates, leading to significant economic losses, often exceeding 50%. Currently, there is a growing interest in identifying biocontrol agents to mitigate peach brown rot, with a predominant interest in Bacillus species.

RESULTS

In this investigation, we isolated 410 isolates of actinomycetes from non-farmland ecosystem soil samples. Subsequently, 27 isolates exhibiting superior inhibitory capabilities were selected. Among these, strain XDS1-5 demonstrated the most robust fungistatic effect against brown rot disease, achieving an 80% inhibition rate in vitro and a 66% inhibition rate in vivo. XDS1-5 was identified as belonging to the Streptomyces virginiae species. Furthermore, a fermentation filtrate of XDS1-5 exhibited the ability to metabolize 34.21% of the tested carbon sources and 7.37% of the tested nitrogen sources. Particularly noteworthy was its capacity to disrupt the cell membrane structure directly, leading to increased cell membrane permeability and cytoplasmic leakage. Additionally, our investigation indicated that indoline, a metabolite produced by XDS1-5, played a pivotal role in inhibiting the growth of M. fructicola.

CONCLUSION

In summary, our study has identified a biocontrol actinomycete, XDS1-5, with the potential to effectively inhibit postharvest brown rot disease in peaches. This finding holds great significance for the biological control of peach brown rot, offering promising prospects for mitigating the economic losses associated with this devastating disease. © 2024 Society of Chemical Industry.

Unlocking the therapeutic potential of bioactive exopolysaccharide produced by marine actinobacterium Streptomyces vinaceusdrappus AMG31: A novel approach to drug development

Acidic exopolysaccharide (EPS) was produced by a marine actinobacterium Streptomyces vinaceusdrappus strain AMG31 with the highest yield of 10.6 g/l. The synthesized EPS has an average molecular weight of 5.1 × 104 g/mol and contains arabinose, glucose, galacturonic acid (0.5:2:2 M ratio), with 39.77 % uronic acid residues and 18.8 % sulfate detected. EPS exhibited antioxidant activities with 93.8 % DPPH radical scavenging and 344.7 μg/mg total antioxidant capacity. It displayed anti-inflammatory effects by inhibiting 5-LOX and COX-2. Regarding the cytotoxic activity, the IC50 values are 301.6 ± 11.8, 260.8 ± 12.2, 29.4 ± 13.5, 351.3 ± 11.2, 254.1 ± 9.8, and 266.5 ± 10.4 μg/ml for PC-3, HEP-2, MCF-7, HCT-116, A-549, HepG-2 respectively, which indicate that the produced EPS does not have strong cytotoxic activities. Moreover, the EPS showed anti-Alzheimer activity via inhibition of the Butyrylcholinesterase enzyme, with the highest percentage of 84.5 % at 100 μg/ml. Interestingly, the EPS showed superior anti-obesity activity by inhibiting lipase enzyme with a rate of 95.3 % compared to orlistat as a positive control (96.8 %) at a concentration of 1000 μg/ml. Additionally, the produced EPS displayed the highest anti-diabetic properties by inhibiting α-amylase (IC50 31.49 μg/ml) and α-glucosidase (IC50 6.48 μg/ml), suggesting antidiabetic potential analogous to acarbose. EPS exhibited promising antibacterial and antibiofilm activity against a wide range of Gram-positive and Gram-negative pathogenic bacteria.

8-Hydroxyquinoline a natural chelating agent from Streptomyces spp. inhibits A549 lung cancer cell lines via BCL2/STAT3 regulating pathways

Biomolecules from Streptomyces spp. are emerging sources of natural drugs and have been focused on over the decade. The discovery of bioactive chemotherapeutic molecules from soil Streptomyces spp. has opened the medium for the search for natural drugs. In the current study, 8-HOQ was extracted and purified from soil Streptomyces spp. and was evaluated on A549 and BEAS cell lines. The apoptotic and caspase mediated pathways were evaluated using cell proliferation, dual fluorescent staining, migration, invasion and mRNA as well as protein quantification of apoptotic markers. In vitro cytotoxicity test revealed that 8-HOQ possesses potent cytotoxicity activities with IC₅₀ values of 26 µM, 5 µM, 7.2 µM at 24 h, 48 h, and 72 h respectively against A549 lung cancer cell lines. The result also demonstrated that 8-HOQ from Streptomyces spp significantly inhibited the A549 lung cancer cell lines and activated the intrinsic pathways of apoptosis. The caspase-3 and caspase-8 activities were potentially elevated in 8-HOQ treated A549 cell lines and confirmed that 8-HOQ mediated A549 cancer cell death through the intrinsic pathway. The results explored caspase-mediated apoptosis as a mechanism underlying the inhibition of cancer cell viability in a dose-dependent manner. The expression of P53, BCL2 and STAT3 were inhibited in A549 cell lines and confirmed the metastasis inhibitory potential of 8-HOQ by blocking migration and invasion in A549 cell lines. These results indicated that 8-HOQ from Streptomyces spp. potentially inhibited growth and migration of A549 lung cancer cell lines.

Bioactive Potential of Several Actinobacteria Isolated from Microbiologically Barely Explored Desert Habitat, Saudi Arabia

Simple Summary

Bioactive natural products have been regarded as promising tools for treatment of various ailments. Among natural sources, actinomycetes have been widely explored for their potential bioactivity. In this regard, the present study has focused on the phytochemical content and biological activities of several actinobacteria isolates, which were investigated for their phenolic and flavonoid content, as well as their antioxidant, antibacterial and antiprotozoal activities. The most active isolates were further investigated for their antileukemic activity, where such isolates were shown to exert cytotoxic activity against the tested cell lines, following a mechanism that might be due to the ability of the active isolate extracts to reduce cyclooxygenase and lipoxygenase activities. Overall, isolation and characterization of the active molecule from the potential actinomycetes strains will pave the way for the development of drugs against human diseases such as blood cancer.

Abstract

Biomolecules from natural sources, including microbes, have been the basis of treatment of human diseases since the ancient times. Therefore, this study aimed to investigate the potential bioactivity of several actinobacteria isolates form Al-Jouf Desert, Saudi Arabia. Twenty-one actinobacterial isolates were tested for their antioxidant (flavonoids, phenolics, tocopherols and carotenoids) content, and biological activities, namely FRAP, DPPH, ABTS, SOS and XO inhibition, anti-hemolytic and anti-lipid peroxidation as well as their antibacterial and antiprotozoal activities. Accordingly, five isolates (i.e., Act 2, 12, 15, 19 and 21) were selected and their 90% ethanolic extracts were used. The phylogenetic analysis of the 16S rRNA sequences indicated that the most active isolates belong to genus Streptomyces. The genus Streptomyces has been documented as a prolific producer of biologically active secondary metabolites against different cancer types. Thus, the anti-blood cancer activity and the possible molecular mechanisms by which several Streptomyces species extracts inhibited the growth of different leukemia cells, i.e., HL-60, K562 and THP-1, were investigated. In general, the five active isolates showed cytotoxic activity against the tested cell lines in a dose dependent manner. Among the potent isolates, isolate Act 12 significantly decreased the cell viability and showed maximum cytotoxic activities against both HL-60 and K562 cells, while isolate Act 15 exhibited maximum cytotoxic activity against THP-1 cells. Moreover, Act 2 and Act 12 reduced cyclooxygenase (COX-2) and lipoxygenase (LOX) activity, which is involved in the proliferation and differentiation of cancer cells and may represent a possible molecular mechanism underlying leukemia growth inhibition. The bioactive antioxidant extracts of the selected Streptomyces species inhibited leukemia cell growth by reducing the COX-2 and LOX activity. Overall, our study not only introduced a promising natural alternative source for anticancer agents, but it also sheds light on the mechanism underlying the anticancer activity of isolated actinomycetes.

Biodiversity in production of antibiotics and other bioactive compounds

Microbes continue to play a highly considerable role in the drug discovery and development process. Nevertheless, the number of new chemical entities (NCEs) of microbial origin that has been approved by the Food and Drug Administration (FDA) has been reduced in the past decade. This scarcity can be partly attributed to the redundancy in the discovered molecules from microbial isolates, which are isolated from common terrestrial ecological units. However, this situation can be partly overcome by exploring rarely exploited ecological niches as the source of microbes, which reduces the chances of isolating compounds similar to existing ones. The use of modern and advanced isolation techniques, modification of the existing fermentation methods, genetic modifications to induce expression of silent genes, analytical tools for the detection and identification of new chemical entities, use of polymers in fermentation to enhance yield of fermented compounds, and so on, have all aided in enhancing the frequency of acquiring novel compounds. These compounds are representative of numerous classes of diverse compounds. Thus, compounds of microbial origin and their analogues undergoing clinical trials continue to demonstrate the importance of compounds from microbial sources in modern drug discovery.