Biologically active secondary metabolites from white-rot fungi

Effects of Ganoderma lucidum Powder on the Growth Performance, Immune Organ Weights, Cecal Microbiology, Serum Immunoglobulins, and Tibia Minerals of Broiler Chickens

A total of 640 one-day-old Cobb 500 MV × Cobb 500 FF mixed broilers were randomly assigned to one of four experimental treatments with four replicates per treatment and 40 birds per replicate for 32 days. The treatments consisted of a basal diet (control group), basal diet + 0.02% zinc bacitracin (AGP group), basal diet + 0.2% G. lucidum powder (GLP; 0.2% GLP group), and basal diet + 0.3% GLP (0.3% GLP group). The results showed that dietary 0.2% GLP supplementation increased body weight compared to the control and 0.3% GLP groups, and decreased feed conversion ratio (FCR) compared to the control group, during 19-32 days (p < 0.05). The feed intake was lower (p < 0.05) in both dietary GLP supplementation groups and the AGP group during 1-8 and 1-32 days compared to the control group. Additionally, the FCR was lower in the dietary GLP supplementation group (0.2%) and the AGP group (p < 0.05) compared to the control group. Moreover, the caeca of broiler chickens in the AGP and 0.2% GLP groups had a higher abundance of lactic acid bacteria (LAB). Supplementation of feed additives (AGP and GLP) increased the relative weight of the thymus, with no effect on the bursa of Fabricius and spleen. However, AGP supplementation decreased the serum IgM concentration, while supplementing a higher dose of GLP (0.3%) increased the ash content in the tibia. The findings indicate that 0.2% GLP is the recommended supplementation dose as a natural growth promoter to replace AGP in apparently normal chickens.

Unappreciated role of secondary metabolism-derived small mediators in degrading bisphenol A and antibiotics by a laccase-expressing fungus

Fungal laccase producers can effectively address bisphenol A (BPA) and antibiotic-contaminated water. However, the role of small mediators produced by fungal secondary metabolism in enhancing the removal of refractory contaminants is often overlooked. In this work, an efficient laccase-producing strain, Trametes hirsuta La-7, was activated to simultaneously treat BPA and antibiotics. Coexisting tetracycline, ciprofloxacin, sulfadiazine, or roxithromycin inhibited fungal cell growth, reducing laccase biosynthesis but largely increasing the formation of syringaldehyde (SYR), 4-hydroxybenzoic acid (HBA), and vanillin (VAN) through a complex regulatory network. These specialized metabolites (i.e., small mediators) acted as diffusible electron carriers for laccase, enabling the oxidative decomposition of the four antibiotics with high redox potentials. According to laccase-mediator-regulated radical random polymerization and decomposition, the identified intermediates of copollutants were parallelly concentrated in oligomeric coupling products and oxidative cleavage species. By inoculating logarithmic phase cell pellets in conjunction with an artificially added small mediator (SYR, HBA, or VAN), the removal efficiencies of BPA and the four antibiotics within 5 d reached 100% and 69-100% in artificial wastewater, respectively. The low and ultimately non-biotoxic intermediate products generated in the fungus-mediator systems mitigated the eco-environmental risks of the parent compounds. This work highlights the previously underappreciated role of secondary metabolism-derived small mediators in enhancing the degradation of BPA and antibiotics by a laccase-expressing fungus and is beneficial to the rational design of a robust fungus-mediator system for environmental bioremediation.

Competitive antagonistic action of laccase between Trichoderma species and the newly identified wood pathogenic Ganoderma camelum

Ganoderma, a well-known genus in the Ganodermataceae family, has caused the extinction of several tree species due to its pathogenicity. This study explored the pathogenic effect of a newly identified Ganoderma species on trees and its competitive efficiency against Trichoderma species. Ganoderma camelum sp. nov. is characterized by small sessile basidiomata and a velvety, soft, camel-brown pileus. Phylogenetic analysis and ITS rDNA sequences indicated that the species were Trichoderma and Ganoderma camelum. Both fungal species competed antagonistically by secreting laccase. The laccase activity of G. camelum, with a value of 8.3 ± 4.0 U/mL, demonstrated the highest competitive activity against Trichoderma species. The laccase produced by T. atroviride (2.62 U/mL) was most effective in countering the pathogenic action of the novel G. camelum. The molecular weights of laccase were determined using SDS-PAGE (62.0 kDa for G. camelum and 57.0 kDa for T. atroviride). Due to the white rot induced by this Ganoderma species in the host tree, G. camelum showed the highest percentage inhibition of radial growth (76.3%) compared to T. atroviride (28.7%). This study aimed to evaluate the competitive antagonistic activity of Ganoderma and Trichoderma on malt extract agar media in the context of white rot disease in the host tree. This study concluded that the laccase from G. camelum caused weight loss in rubber wood blocks through laccase action, indicating tissue injury in the host species. Therefore, it was also concluded that G. camelum was more effective in pathogenic action of the host and resisted the biological action of T. atroviride. In principal components analysis (PCA), all the species associated with laccase exhibited a very strong influence on the variability of the system. The PIRG rate (percentage inhibition of radial growth) was strongly and positively correlated with laccase activity.

Progress in the Study of Natural Antimicrobial Active Substances in Pseudomonas aeruginosa

The prevalence of antimicrobial resistance reduces the effectiveness of antimicrobial drugs in the prevention and treatment of infectious diseases caused by pathogens such as bacteria, fungi, and viruses. Microbial secondary metabolites have been recognized as important sources for new drug discovery and development, yielding a wide range of structurally novel and functionally diverse antimicrobial drugs for the treatment of a variety of diseases that are considered good producers of novel antimicrobial drugs. Bacteria produce a wide variety of antimicrobial compounds, and thus, antibiotics derived from natural products still dominate over purely synthetic antibiotics among the antimicrobial drugs developed and introduced over the last four decades. Among them, Pseudomonas aeruginosa secondary metabolites constitute a richly diverse source of antimicrobial substances with good antimicrobial activity. Therefore, they are regarded as an outstanding resource for finding novel bioactive compounds. The exploration of antimicrobial compounds among Pseudomonas aeruginosa metabolites plays an important role in drug development and biomedical research. Reports on the secondary metabolites of Pseudomonas aeruginosa, many of which are of pharmacological importance, hold great promise for the development of effective antimicrobial drugs against microbial infections by drug-resistant pathogens. In this review, we attempt to summarize published articles from the last twenty-five years (2000-2024) on antimicrobial secondary metabolites from Pseudomonas aeruginosa.

Basidiomycetes Polysaccharides Regulate Growth and Antioxidant Defense System in Wheat

Higher-fungi xylotrophic basidiomycetes are known to be the reservoirs of bioactive metabolites. Currently, a great deal of attention has been paid to the exploitation of mycelial fungi products as an innovative alternative in crop protection. No data exist on the mechanisms behind the interaction between xylotrophic mushrooms' glycopolymeric substances and plants. In this study, the effects of basidiomycete metabolites on the morphophysiological and biochemical variables of wheat plants have been explored. Wheat (Triticum aestivum L. cv. Saratovskaya 29) seedlings were treated with extracellular polysaccharides (EPSs) isolated from the submerged cultures of twenty basidiomycete strains assigned to 13 species and 8 genera. The EPS solutions at final concentrations of 15, 40, and 80 mg/L were applied to wheat seedlings followed by their growth for 10 days. In the plant samples, the biomass, length of coleoptile, shoot and root, root number, rate of lipid peroxidation by malondialdehyde concentration, content of hydrogen peroxide, and total phenols were measured. The peroxidase and superoxide dismutase activity were defined. Most of the EPS preparations improved biomass yields, as well as the morphological parameters examined. EPS application enhanced the activities of antioxidant enzymes and decreased oxidative damage to lipids. Judging by its overall effect on the growth indices and redox system of wheat plants, an EPS concentration of 40 mg/L has been shown to be the most beneficial compared to other concentrations. This study proves that novel bioformulations based on mushroom EPSs can be developed and are effective for wheat growth and antioxidative response. Phytostimulating properties found for EPSs give grounds to consider extracellular metabolites produced in the xylotrophic basidiomycete cultures as an active component capable of inducing plant responses to stress.

Veratryl Alcohol Attenuates the Virulence and Pathogenicity of Pseudomonas aeruginosa Mainly via Targeting las Quorum-Sensing System

Pseudomonas aeruginosa is an opportunistic pathogen that usually causes chronic infections and even death in patients. The treatment of P. aeruginosa infection has become more challenging due to the prevalence of antibiotic resistance and the slow pace of new antibiotic development. Therefore, it is essential to explore non-antibiotic methods. A new strategy involves screening for drugs that target the quorum-sensing (QS) system. The QS system regulates the infection and drug resistance in P. aeruginosa. In this study, veratryl alcohol (VA) was found as an effective QS inhibitor (QSI). It effectively suppressed the expression of QS-related genes and the subsequent production of virulence factors under the control of QS including elastase, protease, pyocyanin and rhamnolipid at sub-inhibitory concentrations. In addition, motility activity and biofilm formation, which were correlated with the infection of P. aeruginosa, were also suppressed by VA. In vivo experiments demonstrated that VA could weaken the pathogenicity of P. aeruginosa in Chinese cabbage, Drosophila melanogaster, and Caenorhabditis elegans infection models. Molecular docking, combined with QS quintuple mutant infection analysis, identified that the mechanism of VA could target the LasR protein of the las system mainly. Moreover, VA increased the susceptibility of P. aeruginosa to conventional antibiotics of tobramycin, kanamycin and gentamicin. The results firstly demonstrate that VA is a promising QSI to treat infections caused by P. aeruginosa.