Bioactive Secondary Metabolites Research Articles

Biological Control of Pseudomonas syringae in Tomato Using Filtrates and Extracts Produced by Alternaria leptinellae

Endophytic fungi offer promising alternatives for sustainable plant disease management strategies, often through the production of bioactive secondary metabolites. This study investigated the biocontrol potential of filtrates and extracts, produced under controlled conditions, from Alternaria leptinellae E138 against Pseudomonas syringae in tomato plants under greenhouse conditions. To understand the main mechanisms involved in biocontrol, the direct inhibition of bacterial growth and disruption of quorum sensing activity caused by metabolites were studied in vitro, as well as indirect mechanisms, such as their capacity to produce phytohormone-like substances, nutrient mobilization, and antioxidant activity, which can enhance plant growth and fitness. Moreover, a mass spectrometry analysis was used to tentatively identify the secondary metabolites present in the extract with antimicrobial properties, which could explain the biocontrol effects observed. Mycopriming assays, involving the direct treatment of tomato seeds with the fungal A. leptinellae E138 extracts, produced increased germination rates and seedling vigor in tomato seeds. As another treatment, postemergence application of the extracts in greenhouse conditions significantly improved plant health and resulted in a 41% decrease in disease severity. Overall, this study underscores the potential of A. leptinellae E138 extract as a plant growth promoter with biocontrol capabilities, offering promising avenues for sustainable plant disease management.

Revisiting Xylaria diversity in Southern China: Descriptions of 40 new species

AbstractThe genus Xylaria comprises a diverse group of fungi with a global distribution and significant ecological importance, known for being a source of bioactive secondary metabolites with antibacterial, antioxidative, anticarcinogenic, and additional properties. In this study, we present a comprehensive taxonomic revision of the species of Xylaria found in some parts of southern China, characterized by an extensive multilocus phylogeny analysis based on internal transcribed spacer (ITS), TUB2 (β‐tubulin), and DNA‐directed RNA polymerase II subunit 2 (rpb2) gene regions. Morphological examination and detailed comparative analyses of the collected specimens were conducted to determine the distinctiveness of each species. The multilocus phylogeny approach allowed us to infer evolutionary relationships and assess species boundaries accurately, leading to the identification of 40 novel Xylaria species hitherto unknown to science. The newly described species are: X. baoshanensis, X. bawanglingensis, X. botryoidalis, X. dadugangensis, X. doupengshanensis, X. fanglanii, X. glaucae, X. guizhouensis, X. japonica, X. jinghongensis, X. jinshanensis, X. kuankuoshuiensis, X. liboensis, X. negundinis, X. orbiculati, X. ovata, X. pseudoanisopleura, X. pseudocubensis, X. pseudobambusicola, X. pseudoglobosa, X. pseudohemisphaerica, X. pseudohypoxylon, X. puerensis, X. qianensis, X. qiongzhouensis, X. rhombostroma, X. serratifoliae, X. shishangensis, X. shuqunii, X. shuangjiangensis, X. sinensis, X. tongrenensis, X. umbellata, X. xishuiensis, X. yaorenshanensis, X. yinggelingensis, X. yumingii, X. yunnanensis, X. zangmui, and X. zonghuangii. The study's findings shed light on the distinctiveness of the newly described species, supported by both morphological distinctions and phylogenetic relationships with their close relatives. This taxonomic revision significantly contributes to our understanding the diversity of Xylaria in China and enriches the knowledge of fungal biodiversity worldwide.

Insights into the phytochemical composition and antioxidant potential of the Tunisian Ceratonia siliqua L.

Carob (Ceratonia siliqua L.) corresponds to an evergreen leguminous tree (Fabaceae family). The high phenolic content of numerous parts of carob has been deeply associated with several nutritional and functional benefits. The aim of this study was to investigate the physicochemical properties of ground carob pods and seeds, the effect of different extraction procedures as well a comprehensive phytochemical characterization of hydro-methanolic extracts (80/20 v/v) of pods and seeds by HPLC-DAD ESI-Q-TOF-MS/MS. Additionally, their antioxidant activity was evaluated using in vitro assays.The results showed thatthe dry matter (DM) values were 88.09% for pods and 89.10% for seeds, protein contents were 0.41 g/100 g DM for pods and 0.88 g/100 g DM for seedsand total sugars contents were 0.35 g/100 DM for pods and 26.70 g/100 g DM for seeds. Furthermore, the oil holding capacities (OHC) were 10.43 g/g for pods and 7.53 g/g for seeds, while the water holding capacities were 8.46 g/g for pods and 2.59 g/g for seeds.The hydro-methanolic extracts of both pods and seeds showed the presence of 53 secondary bioactive metabolites belonging to various classes(flavonoids, phenolic acids, tannins and non-phenolic compounds). The antioxidant activities were evidenced in DPPH (22.24 mg/ml for pods and 26.37 mg/ml for seeds), ABTS (198.50 mmol Eq Trolox/100 g for pods and 201.04 mmol Eq Trolox/100 g for seeds) and FRAP (0.39 mmol Eq Trolox/100 g for pods and 0.53 mmol Eq Trolox/100 g for seeds).Moreover,high significant (p ≤ 0.01) correlation coefficients were found between the antioxidant activity estimated by the DPPH method and total phenols (r = 0.943), orthodiphenols (r = 0.996), flavonoids (r = 0.880) and flavonols (r = 0.982). Nevertheless, lower correlations were detected with ABTS and FRAP methods.These results demonstrated that carob parts displayed an interesting potential that can be of interest for further valorizations as a natural antioxidant with multiple applications, namely functional food ingredients or prevention of many health problems.

Integrating Biological Control Agents for Enhanced Management of Apple Scab (Venturia inaequalis): Insights, Risks, Challenges, and Prospects

Apple scab incited by the ascomycete Venturia inaequalis poses a significant threat to apple cultivation, necessitating a reassessment of existing disease management strategies. Attempts to manage apple scab include diverse approaches like developing disease forecasting models and the extensive application of synthetic chemical fungicides. However, the efficacy of these methods is compromised by inconsistencies, environmental concerns, and the pathogen’s resistance, necessitating the exploration of alternative sustainable strategies. Addressing the challenges associated with apple scab management, this review strongly supports a shift towards the integration of biological control agents (BCAs). Emphasising the transformative synergy between BCAs and their bioactive secondary metabolites, we highlight their efficacy in advancing precision disease control through innovative and sustainable solutions. The review effectively presents a strong justification for the integration of BCAs and their by-products into apple scab management, offering insights into associated benefits, risks, and challenges while outlining promising prospects. Ultimately, it is expected to drive the adoption of environmentally conscious practices for effective apple scab management.

Cyclodextrin-assisted extraction as a green alternative for the recovery of phenolic compounds from Helichrysum plicatum DC. flowers

Helichrysum plicatum DC. is an important source of bioactive secondary metabolites with a variety of pharmacological activities. To obtain highly potent extracts with the maximum level of phenolic glycosides and total phenolic compounds, this study aimed to establish an eco-friendly cyclodextrin-assisted extraction procedure from H. plicatum flowers. Response surface methodology (RSM) and artificial neural networks (ANN) were used to optimize the ultrasound-assisted extraction (UAE) by evaluating sonication temperature, time, concentrations of ethanol and two types of cyclodextrins (β-CD and HP-β-CD). Comprehensive statistical validation revealed better predicting capacity of the created ANN models compared to the traditional RSM. The highest positive effects were observed for the ethanol concentration and the extraction temperature. Both types of CDs showed not only positive impact on the extraction efficiency of bioactives, but also on their stability after exposure to stress conditions. Molecular docking was used to additionally reveal interactions within the studied inclusion complexes. Conclusively, the HP-β-CD-assisted extraction conducted at 80 °C for 40 min, utilizing 62% ethanol and 1.60% HP-β-CD, was the most optimal due to its ability to minimize ethanol consumption while achieving maximal recovery of bioactives, in comparison to β-CD (80%). Under these optimized conditions, experimentally obtained results for isoquercitrin (0.50 mg/g DW), kaempferol-3-O-glucoside (5.83 mg/g DW), apigenin-7-O-glucoside (1.34 mg/g DW), and total polyphenolic (28.51 mg GAE/g DW) content were in agreement with the values predicted by ANN.

Metabolomics Approach to Explore Bioactive Natural Products Derived From Plant-Root-Associated Streptomyces.

Streptomyces, a prominent genus within the Actinomycetota phylum, is responsible for over 60% of clinically relevant antibiotics. Streptomyces strains inhabiting plant roots possess the potential to synthesize bioactive natural products, conferring defense and resilience to plants against pathogenic microorganisms. However, this potential remains largely unexplored. This study aims to screen for bioactive metabolites produced by Streptomyces strains in the plant rhizosphere.Six Streptomyces isolates were cultivated using three modified media to induce the production of diverse metabolites, employing the One Strain Many Compounds (OSMAC) approach. The metabolites present in extracts from fermentation broths were examined through a non-targeted Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS) approach coupled with Global Natural Products Social Molecular Networking (GNPS MN). The antimicrobial activity of the extracts was assessed using the disc diffusion method.The strains demonstrated a wide-ranging antimicrobial efficacy against all examined organisms. The GNPS molecular network analyses reveal that metabolite profiles in extracts can exhibit variations based on the medium and solvent system employed. Notably, the ethyl acetate and dichloromethane extracts from Streptomyces sp. CAH29, cultivated in Glucose-Yeast Extract Medium (GYM), exhibited inhibition diameters of up to 30mm against both Staphylococcus aureus and Candida albicans. Within the metabolomes of these strains, the antibiotics spiramycin and actinomycin were detected. Additionally, lyngbatoxin, a tumor promoter, and potential new analogs were identified. Significantly, a considerable portion of the produced metabolites did not align with any known compounds, indicating the existence of unidentified metabolites generated by these strains. This suggests the possibility of introducing novel chemical entities.Our study illustrated that Streptomyces strains associated with plant roots could be considered a valuable source of bioactive secondary metabolites. Furthermore, the metabolomics approach utilized in this study serves as a rapid and valuable tool for the screening of microorganisms capable of producing bioactive metabolites.

Endophytic fungus from Gynura japonica: phytochemical screening, biological activities, and characterisation of its bioactive compound

The research aims to identify the chemical constituents of endophytic fungi associated with Gynura japonica and their biological activities. Two endophytic fungi, labelled as GS-1 and GS-2, have been isolated from the leaves of G. japonica. They were cultivated on white rice media for their optimum cultivation time. Cultivated fungi were extracted with ethyl acetate and concentrated to give a crude extract. All crude extracts were evaluated for their phytochemical screening and assayed for their antibacterial and antioxidant activities. Based on the results, fungal GS-1 was the most potential fungus to produce bioactive secondary metabolites and identified as Dimorphiseta acuta. A bioactive compound was isolated from crude extract of fungal D. acuta and identified as emodin. To the best of our knowledge, the study of secondary metabolite and its biological activity of endophytic fungus colonised with the leaves of G. japonica is reported here for the first time.

Antimicrobial Action Mechanisms of Natural Compounds Isolated from Endophytic Microorganisms.

Infectious diseases are a significant challenge to global healthcare, especially in the face of increasing antibiotic resistance. This urgent issue requires the continuous exploration and development of new antimicrobial drugs. In this regard, the secondary metabolites derived from endophytic microorganisms stand out as promising sources for finding antimicrobials. Endophytic microorganisms, residing within the internal tissues of plants, have demonstrated the capacity to produce diverse bioactive compounds with substantial pharmacological potential. Therefore, numerous new antimicrobial compounds have been isolated from endophytes, particularly from endophytic fungi and actinomycetes. However, only a limited number of these compounds have been subjected to comprehensive studies regarding their mechanisms of action against bacterial cells. Furthermore, the investigation of their effects on antibiotic-resistant bacteria and the identification of biosynthetic gene clusters responsible for synthesizing these secondary metabolites have been conducted for only a subset of these promising compounds. Through a comprehensive analysis of current research findings, this review describes the mechanisms of action of antimicrobial drugs and secondary metabolites isolated from endophytes, antibacterial activities of the natural compounds derived from endophytes against antibiotic-resistant bacteria, and biosynthetic gene clusters of endophytic fungi responsible for the synthesis of bioactive secondary metabolites.

Two New and One First Recorded Species of Xylaria Isolated from Fallen Leaves in Hainan Tropical Rainforest National Park in China

Xylaria is a widely distributed genus in the Ascomycota phylum that can decompose wood. It is an essential decomposer in ecosystems and a source of bioactive secondary metabolites. Based on morphological characteristics and molecular evidence, this article thoroughly describes two new species discovered on the fallen leaves in Hainan Tropical Rainforest National Park, along with illustrations and comparisons with similar species. Xylaria diaoluoshanensis is characterized by filamentous stromata with long infertile apexes, ascospores sometimes with non-cellular appendages. Xylaria fulvotomentosa differentiates itself from other Xylaria species that grow on fallen leaves by its stroma surface, being yellow tomentose. These two new species of the genus Xylaria were found by phylogenetic analysis using the ITS-β-tubulin-RPB2 sequence dataset. Furthermore, a species first discovered in China, X. petchii, is described. Finally, a search table for 44 species related to fallen leaves and petioles in the world is established.

Induction, Proliferation and Differentiation of Callus in Paris polyphylla Sm. through Leaf Culture

Paris polyphylla Sm. is a vulnerable medicinal plant employed in the treatment of various ailments. This study seeks to establish a protocol for callus induction, proliferation, and differentiation of P. polyphylla. Immature leaf explants were cultured on MS medium with varying concentrations of plant growth regulators (PGRs), including 2,4-dichlorophenoxyacetic acid (2,4-D), kinetin (Kn), 6-benzylaminopurine (BAP), Thidiazuron (TDZ), α-Naphthalene acetic acid (NAA), and Gibberellic acid (GA3), along with 10% coconut water. After 12 weeks of primary culture, the optimal callus induction was observed in MS medium supplemented with 0.25 mg/l 2,4-D + 0.5 mg/l Kn. In the secondary culture at 8 weeks, the best callus proliferation, as determined by callus weight or growth index, occurred in MS medium supplemented with 2.0 mg/l BAP alone, 2.0 mg/l Kn alone, 1.0 mg/l TDZ alone, combinations of 2.0 mg/l Kn + 1.0 mg/l BAP + 2.0 mg/l GA3, and combinations of 0.5 mg/l NAA + 2.0 mg/l BAP + 2.0 mg/l GA3, as well as 10% coconut water. Furthermore, callus differentiation into mini rhizomes with root primordia was successfully achieved in MS media containing 2.5 mg/l Kn and 10% coconut water. This study reports, for the first time, the formation and differentiation of callus from leaf explants in P. polyphylla. Large-scale callus generation from leaf explants has the potential to enhance the production of bioactive secondary metabolites for therapeutic purposes and facilitate the development of plantlets through organogenesis.

Saccharomyces cerevisiae Bioactive Metabolites: Characterization and Biological Activities

AbstractThis study aimed to extract bioactive secondary metabolites, determine volatile organic compounds, and polyphenols using GC/MS and LC/MS, and assess their total phenolic content, antimicrobial, antioxidant, and cytotoxic properties. The chemical analysis of S. cerevisiae NRLL Y‐12633 ethyl acetate extract revealed eight volatile organic components, whereas the main component was phenyl ethyl alcohol (77.39 %). On the other hand, nineteen volatile organic compounds were identified in the ethyl acetate extract of S. cerevisiae NRRL Y‐1089, whereas the most critical component was 2, 3‐butanediol (60.74 %). The most abundant phenolic acids were syringic acid (25476.46 ng/mL), and cinnamic acid (5163.76 ng/mL) in the ethyl acetate extracts of S. cerevisiae NRLL Y‐12633 and S. cerevisiae NRRL Y‐1089 respectively. Flavonoid, naringenin, was also found in the ethyl acetate extract of S. cerevisiae NRLL Y‐12633, whereas daidzein and rutin were detected in the ethyl acetate extract of S. cerevisiae NRRL Y‐1089. The total phenolic content of S. cerevisiae NRRL Y‐12633 ethyl acetate extract was found to be greater than that of S. cerevisiae NRRL Y‐1089 ethyl acetate extract. Data revealed that S. cerevisiae ethyl acetate extracts displayed antioxidant and antimicrobial activity, whereas only the ethyl acetate extract of S. cerevisiae NRRL Y‐1089 showed anticancer activity.

Penicillium janthinellum: A Potential Producer of Natural Products

Penicillium is a kind of common filamentous fungi yielding high levels of secondary metabolites with diverse structures and attractive activities. Among these fungi, Penicillium janthinellum is a potential producer of secondary metabolites whose natural products have been noticed due to their various chemical structures and biological activities. This review summarizes the sources, distribution, bioactivities and structural characteristics of compounds isolated from P. janthinellum from 1980 to 2023. A total of 153 natural products have been isolated from P. janthinellum, of which 65 were new compounds. The compounds separated from P. janthinellum exhibit diverse skeletal chemical structures, concentrated in the categories of polyketides (40%), alkaloids (31%) and terpenoids (14%). P. janthinellum-derived compounds display attractive biological activities, such as cytotoxic, antibacterial, antifungal and antiviral activities. These results indicate that P. janthinellum is a potential fungus for producing bioactive secondary metabolites which can be used as precursors for new drugs.

Recent Developments and Future Prospects of Natural Antimicrobial Bioactive Metabolites Obtained from Endophytic Bacterial Isolate

Background: Adathoda beddomei (Adosa), a kind of softwood, evergreen, perennial shrub, has been used as a source of endophyte bacteria. Adhatoda beddomei has a wide variety of chemicals, including anthocyanins, aminophylline, alkaloids, cardiac glycosides, isoprenaline, triterpenoids, resins, flavonoids, tannins, sterol, saponins, etc. The root, stem, and leaf parts of Adathoda beddomei are most often used in indigenous medicine. Moreover, the root bark is also used to cure several conditions, including leprosy, fever, and bleeding. Objective: Some important bioactive metabolites were obtained from endophytes bacteria and analyzed through various techniques (NMR, MASS, FTIR, HPLC, and UV- spectrophotometer) for their bioactive secondary metabolites. Methods: In silico calculation was performed to reveal bioactive metabolites with the potential to be antibacterial, and their primary mode of action may include dissolving bacterial and fungal cell walls. Results: The antimicrobial activity of Adathoda beddomei was demonstrated against different pathogenic and non-pathogenic bacteria. Identification of endophytes was done based on external morphological characteristics with the help of a scanning electron microscope (SEM). Conclusion: Natural compounds derived from endophyte bacteria with a very low molecular mass can be used to discover new and important structures for different pharmaceuticals and agrochemicals.

Structures and Biological Activities of Secondary Metabolites from Xylaria spp.

The fungus genus Xylaria is an important source of drug discoveries in scientific fields and in the pharmaceutical industry due to its potential to produce a variety of structured novel and bioactive secondary metabolites. This review prioritizes the structures of the secondary metabolites of Xylaria spp. from 1994 to January 2024 and their relevant biological activities. A total of 445 new compounds, including terpenoids, nitrogen-containing compounds, polyketides, lactones, and other classes, are presented in this review. Remarkably, among these compounds, 177 compounds show various biological activities, including cytotoxic, antimicrobial, anti-inflammatory, antifungal, immunosuppressive, and enzyme-inhibitory activities. This paper will guide further investigations into the structures of novel and potent active natural products derived from Xylaria and their potential contributions to the future development of new natural drug products in the agricultural and medicinal fields.

What Is New about Parsley, a Potential Source of Cardioprotective Therapeutic Substances?

Petroselinum crispum (Mill.) Fuss (Apiaceae), popularly known as parsley, is a ubiquitous aromatic herb used for culinary and medicinal purposes worldwide. In addition to the richness in nutrients, several bioactive secondary metabolites, especially the flavone apigenin and its glycosides, have been described in this species. Parsley has already been shown to have several health-promoting activities, such as antithrombotic, antihypertensive, and hypolipidemic properties. The multiple studies conducted in animal models so far suggest this species is a potential source of cardioprotective agents. This review provides up-to-date information and perspectives on the potential of parsley and its bioactive compounds for the development of nutraceutical products and drugs for promoting cardiovascular health. It includes not only a discussion of parsley’s reported bioactivities but also the knowledge of supplements and food additives developed as innovative parsley-based products.

Alpha-sitosterol: a new antiviral agent produced by Streptomyces misakiensis and its potential activity against Newcastle disease virus

BackgroundNewcastle Disease Virus (NDV) causes severe economic losses in the poultry industry worldwide. Hence, this study aimed to discover a novel bioactive antiviral agent for controlling NDV. Streptomyces misakiensis was isolated from Egyptian soil and its secondary metabolites were identified using infrared spectroscopy (IR), gas chromatography–mass spectrometry (GC–MS), and nuclear magnetic resonance (NMR) spectroscopy. The inhibitory activity of bioactive metabolite against NDV were examined. Three experimental groups of 10-day-old specific pathogen-free embryonated chicken eggs (SPF-ECEs), including the bioactive metabolite control group, NDV control positive group, and α-sitosterol and NDV mixture-treated group were inoculated.Resultsα-sitosterol (Ethyl-6-methylheptan-2-yl]-10,13-dimethyl-dodecahydro-1H-cyclopenta[a]phenanthren-3-ol), a secondary metabolite of S. misakiensis, completely inhibited hemagglutination (HA) activity of the NDV strain. The HA activity of the NDV strain was 8 log2 and 9 log2 for 0.5 and 0.75% RBCs, respectively. The NDV HA activity for the two concentrations of RBCs was significantly (P < 0.0001) inhibited after α-sitosterol treatment. There was a significant (P < 0.0001) decrease in the log 2 of HA activity, with values of − 0.500 (75%, chicken RBCs) before inoculation in SPF-ECEs and − 1.161 (50%, RBCs) and − 1.403 (75%, RBCs) following SPF-ECE inoculation. Compared to ECEs inoculated with NDV alone, the α-sitosterol-treated group showed improvement in histological lesion ratings for chorioallantoic membranes (CAM) and hepatic tissues. The CAM of the α-sitosterol- inoculated SPF-ECEs was preserved. The epithelial and stromal layers were noticeably thicker with extensive hemorrhages, clogged vasculatures, and certain inflammatory cells in the stroma layer in the NDV group. However, mild edema and inflammatory cell infiltration were observed in the CAM of the treated group. ECEs inoculated with α-sitosterol alone showed normal histology of the hepatic acini, central veins, and portal triads. Severe degenerative alterations, including steatosis, clogged sinusoids, and central veins, were observed in ECEs inoculated with NDV. Mild hepatic degenerative alterations, with perivascular round cell infiltration, were observed in the treated group.ConclusionTo the best of our knowledge, this is the first study to highlight that the potentially bioactive secondary metabolite, α-sitosterol, belonging to the terpene family, has the potential to be a biological weapon against virulent NDV. It could be used for the development of innovative antiviral drugs to control NDV after further clinical investigation.

A Bacillus velezensis strain shows antimicrobial activity against soilborne and foliar fungi and oomycetes.

Biological control uses naturally occurring antagonists such as bacteria or fungi for environmentally friendly control of plant pathogens. Bacillus spp. have been used for biocontrol of numerous plant and insect pests and are well-known to synthesize a variety of bioactive secondary metabolites. We hypothesized that bacteria isolated from agricultural soil would be effective antagonists of soilborne fungal pathogens. Here, we show that the Delaware soil isolate Bacillus velezensis strain S4 has in vitro activity against soilborne and foliar plant pathogenic fungi, including two with a large host range, and one oomycete. Further, this strain shows putative protease and cellulase activity, consistent with our prior finding that the genome of this organism is highly enriched in antifungal and antimicrobial biosynthetic gene clusters. We demonstrate that this bacterium causes changes to the fungal and oomycete hyphae at the inhibition zone, with some of the hyphae forming bubble-like structures and irregular branching. We tested strain S4 against Magnaporthe oryzae spores, which typically form germ tubes and penetration structures called appressoria, on the surface of the leaf. Our results suggest that after 12 hours of incubation with the bacterium, fungal spores form germ tubes, but instead of producing appressoria, they appear to form rounded, bubble-like structures. Future work will investigate whether a single antifungal molecule induces all these effects, or if they are the result of a combination of bacterially produced antimicrobials.

Vine-Winery Byproducts as Precious Resource of Natural Antimicrobials: In Vitro Antibacterial and Antibiofilm Activity of Grape Pomace Extracts against Foodborne Pathogens.

Grape pomace is the main by-product of vine-winery chains. It requires adequate treatment and disposal but is also an economically underused source of bioactive plant secondary metabolites. This study aimed to investigate the antibacterial effects of polyphenolic extracts from Aglianico (Vitis vinifera L.) grape pomace. In particular, hydroethanolic extracts obtained via an ultrasonic-assisted extraction technique were selected for antimicrobial tests. The extracts were screened for their antibacterial effects against foodborne pathogens that were both Gram-positive, in the case of Staphylococcus aureus and Bacillus cereus, and Gram-negative, in the case of Escherichia coli and Salmonella enterica subsp. enterica serovar Typhimurium, showing variable bacteriostatic and bactericidal effects. In addition, our results demonstrated that the tested grape pomace extracts can reduce the inhibitory concentration of standard antibiotics. Interestingly, selected extracts inhibited biofilm development by S. aureus and B. cereus. Overall, these new insights into the antibacterial properties of grape pomace extracts may represent a relevant step in the design of novel therapeutic tools to tackle foodborne diseases, and in the management of resistant biofilm-related infections.

Discovery of an antitumor compound from xenorhabdus stockiae HN_xs01.

Xenorhabdus, known for its symbiotic relationship with Entomopathogenic nematodes (EPNs), belongs to the Enterobacteriaceae family. This dual-host symbiotic nematode exhibits pathogenic traits, rendering it a promising biocontrol agent against insects. Our prior investigations revealed that Xenorhabdus stockiae HN_xs01, isolated in our laboratory, demonstrates exceptional potential in halting bacterial growth and displaying anti-tumor activity. Subsequently, we separated and purified the supernatant of the HN_xs01 strain and obtained a new compound with significant inhibitory activity on tumor cells, which we named XNAE. Through LC-MS analysis, the mass-to-nucleus ratio of XNAE was determined to be 254.24. Our findings indicated that XNAE exerts a time- and dose-dependent inhibition on B16 and HeLa cells. After 24h, its IC50 for B16 and HeLa cells was 30.178µg/mL and 33.015µg/mL, respectively. Electron microscopy revealed conspicuous damage to subcellular structures, notably mitochondria and the cytoskeleton, resulting in a notable reduction in cell numbers among treated tumor cells. Interestingly, while XNAE exerted a more pronounced inhibitory effect on B16 cells compared to HeLa cells, it showed no discernible impact on HUVEC cells. Treatment of B16 cells with XNAE induced early apoptosis and led to cell cycle arrest in the G2 phase, as evidenced by flow cytometry analysis. The impressive capability of X. stockiae HN_xs01 in synthesizing bioactive secondary metabolites promises to significantly expand the reservoir of natural products. Further exploration to identify the bioactivity of these compounds holds the potential to shed light on their roles in bacteria-host interaction. Overall, these outcomes underscore the promising potential of XNAE as a bioactive compound for tumor treatment.

Soil Actinomycetes as Promising Alternative to Synthetic Herbicides

&#x0D; Weed management is a key agronomic practice in agriculture. Since decades, synthetic herbicides played an indispensable role in weed control due to high effectiveness. However, recently there has been growing interest on exploring alternative weed control methods due to negative impacts of synthetic herbicides on the environment. Besides, there is an increasing demand for organic farm products. Actinomycetes, a group of filamentous, Gram-positive bacteria known for their bioactive secondary metabolites, have emerged as potential candidates for bioherbicides. In this study, we investigated herbicidal potential of twenty-three morphologically distinct actinomycetes strains isolated from soil using lettuce (Lactuca sativa) as a model plant. Eight weeks-old cell-free culture fermentation broth of actinomycetes strains were used for screening the effect on seed germination and seedling growth. Lettuce seeds were exposed to fermentation broth for two weeks while for control, sterilized distilled water was used. Ten seeds per treatment in three replicates were used. The results showed that sixteen actinomycetes strains, ACM25, 26, 29, 33, 34, 35, 36, 38, 41, 42, 43, 47, 48, 49.1 and 49.2 and ACM50 were able to completely inhibit seed germination while seeds treated with ACM32 did not produce roots although seed germination had initiated. It appears that these seventeen strains would be effective at pre-emergence weed control. Seeds that treated with the rest of the six strains had no effect on the seed germination. However, seedlings of ACM24, 45 and ACM46-treated seeds showed deaths by two weeks. Their gradual death started with discoloration of leaves followed by watery rotting of the entire plant. Seedlings of ACM30, 31, 37- treated seeds survived, and their growth performance were observed for two weeks compared to the control. Seedlings were dwarf and exhibited growth deformations such as reduced leaf size, chlorosis, leaf curling and stunted roots. Further, number of leaves, shoot length and root length were significantly different (p&lt;0.05) from that of the control. These observations suggest that the effect of ACM24, 30, 31, 37, 45 and ACM46 would be systemic. In conclusion, our results clearly showed strong herbicidal effects of all tested twenty-three strains of actinomycetes at pre- and post- emergence stages of seed germination. Thus, they can be promising candidates for bioherbicide formulations.&#x0D; &#x0D; Keywords: Actinomycetes, Bioherbicides, Weed management, Sustainable agriculture