Antimicrobial properties of phytohormone (gibberellins) against phytopathogens and clinical pathogens

Initial culture media pH influences the antibacterial activity and metabolic footprint of Lactobacillus acidophilus BIOTECH 1900

This study investigated the impact of initial culture media pH on the antibacterial properties and metabolic profile of cell-free supernatants (CFSs) from Lactobacillus acidophilus BIOTECH 1900 (LAB1900). The CFSs harvested from LAB1900 grown in de Man, Rogosa, Sharpe broth with initial pH of 5.5 (CFS5.5) and 6.6 (CFS6.6) were tested. The two CFSs elicited varying degrees of activity against three gram-negative bacteria. In the agar-well diffusion against Pseudomonas aeruginosa, CFS5.5 and CFS6.6 recorded 14.36 ± 1.34 and 13.06 ± 1.29 mm inhibition, respectively. Interestingly, against Klebsiella pneumoniae, CFS5.5 showed 14.36 ± 1.56 mm inhibition which was significantly higher than the 12.22 ± 1.31 mm inhibition of CFS6.6 (p = 0.0464). While against Acinetobacter baumannii, significantly higher inhibition of 10.66 ± 0.51 mm was observed in CFS6.6 compared to the 7.58 ± 1.93 mm inhibition of CFS5.5 (p = 0.0087). Nonetheless, both CFSs were bactericidal, with a minimum inhibitory and bactericidal concentration range of 3.90625-7.8125 mg/mL. The varied antibacterial activities may be attributed to the metabolite compositions of CFSs. A total of 152 metabolites driving the separation between CFSs were noted, with the majority upregulated in CFS5.5. Furthermore, 15 were putatively identified belonging to acylcarnities, vitamins, gibberellins, glycerophospholipids, and peptides. In summary, initial culture media pH affects the production of microbial metabolites with antibacterial properties.

Sesquiterpenes of the ectomycorrhizal fungus Pisolithus microcarpus alter root growth and promote host colonization

Trees form symbioses with ectomycorrhizal (ECM) fungi, maintained in part through mutual benefit to both organisms. Our understanding of the signaling events leading to the successful interaction between the two partners requires further study. This is especially true for understanding the role of volatile signals produced by ECM fungi. Terpenoids are a predominant class of volatiles produced by ECM fungi. While several ECM genomes are enriched in the enzymes responsible for the production of these volatiles (i.e., terpene synthases (TPSs)) when compared to other fungi, we have limited understanding of the biochemical products associated with each enzyme and the physiological impact of specific terpenes on plant growth. Using a combination of phylogenetic analyses, RNA sequencing, and functional characterization of five TPSs from two distantly related ECM fungi (Laccaria bicolor and Pisolithus microcarpus), we investigated the role of these secondary metabolites during the establishment of symbiosis. We found that despite phylogenetic divergence, these TPSs produced very similar terpene profiles. We focused on the role of P. microcarpus terpenes and found that the fungus expressed a diverse array of mono-, di-, and sesquiterpenes prior to contact with the host. However, these metabolites were repressed following physical contact with the host Eucalyptus grandis. Exposure of E. grandis to heterologously produced terpenes (enriched primarily in γ -cadinene) led to a reduction in the root growth rate and an increase in P. microcarpus-colonized root tips. These results support a very early putative role of fungal-produced terpenes in the establishment of symbiosis between mycorrhizal fungi and their hosts.

Ultra-High Performance Liquid Chromatography-Tandem Mass Spectrometry Identification of Metabolites in Winterberry Fruit Putatively Associated with Natural Disease Resistance to Diaporthe ilicicola

Winterberry holly (Ilex verticillata) is an ornamental plant popularly used in landscape design and sold as cut branches for fall and winter seasonal decoration. Latent fruit rot of winterberry is an emerging disease caused by the fungus Diaporthe ilicicola, which can result in up to 100% crop loss. Diaporthe ilicicola infects open flowers in spring, but symptom onset does not occur until the end of the growing season when the fruit is fully mature. This study was conducted to identify compounds displaying significant variation in abundance during fruit maturation and that may be putatively associated with natural disease resistance observed when the fruit is immature. Winterberry 'Sparkleberry' fruits collected at four timepoints during the 2018 and 2019 seasons were extracted in methanol and analyzed using high resolution ultra-high performance liquid chromatography-tandem mass spectrometry. The results showed a distinct separation of metabolic profiles based on fruit phenological stage. The top 100 features that were differentially expressed between immature and mature fruit were selected from both electrospray ionization (ESI) (-) and ESI (+) datasets for annotation. Eleven compounds shown to decrease throughout the season included cinnamic acids, a triterpenoid, terpene lactones, stilbene glycosides, a cyanidin glycoside, and a furopyran. Nine compounds shown to accumulate throughout the season included chlorogenic acid derivatives, hydrolysable tannins, flavonoid glycosides, and a triterpene saponin. Future research will further confirm the exact identity of the compounds of interest and determine whether they are biologically active toward D. ilicicola or I. verticillata. The results could inform breeding programs, chemical management programs, and novel antifungal compound development pipelines.

A novel method for the extraction and characterization of metabolites from Basidiomycota: Pleurotus ostreatus (Jacq.) P. Kumm., 1871 as a case study

In recent years, the interest in the exploitation of fungal metabolites has grown considerably, given their application in numerous sectors involving human health. However, their identification and characterization by conventional analytical approaches is generally limited to single families of molecules per method of analysis. This constitutes a limiting factor of primary importance in the study of both the metabolic pattern of a single fungal sample and the discovery of its possible applications. In this work, a reverse‐phase high‐performance liquid chromatography coupled with mass spectrometry method for the profile determination of primary and secondary metabolites produced by the oyster‐mushroom Pleurotus ostreatus (Jacq.) P. Kumm., 1871, has been developed. By using a concomitant extraction in three different polarity‐decreasing solvents, namely methanol, ethanol, and acetonitrile, this method allowed the simultaneous analysis of all extracted metabolites belonging to the widest possible range of chemical families, giving an advantage for both qualitative and quantitative determination of known and unknown compounds. The method appears to be valuable and robust for the study of complex matrices like raw fungi extract such as those of Pleurotus ostreatus cultivated on different substrates and/or exposed to multiple stressors.

Metabolic Profiling for the Discovery of Structurally Diverse Gibberellins and Their Precursors from the Endophytic Fungus Fusarium sp. NJ-F5

Gibberellins (GAs) are well-known tetracyclic diterpenoid phytohormones since the 1950s. In this work, eight skeletally diverse GAs (1-8) including four new compounds (1-4), and three known ent-kaurene diterpenoids (9-11), were isolated from the endophytic fungus Fusarium sp. NJ-F5 by integrating mass spectrometry (MS)- and nuclear magnetic resonance (NMR)-based metabolic profiling. Their planar structures and stereochemistry were determined by extensive spectroscopic analyses including MS, NMR, as well as electronic circular dichroism and their calculations, together with single-crystal X-ray diffraction studies. As far as we know, this is a rare report of naturally occurring GAs and their detailed spectroscopic data including MS and NMR in recent decades. Compound 1, as a new member of GAs family, showed an obvious promoting effect on the seedling's growth ofArabidopsis thaliana.

Parthenium hysterophorus's Endophytes: The Second Layer of Defense against Biotic and Abiotic Stresses

Parthenium hysterophorus L. is considered an obnoxious weed due to its rapid dispersal, fast multiplications, and agricultural and health hazards. In addition to its physio-molecular and phytotoxic allelochemical usage, this weed most probably uses endophytic flora as an additional line of defense to deal with stressful conditions and tolerate both biotic and abiotic stresses. The aim of this article is to report the diversity of endophytic flora (fungi and bacteria) in P. hysterophorus and their role in the stress mitigation (biotic and abiotic) of other important crops. Various endophytes were reported from P. hysterophorus and their roles in crops evaluated under biotic and abiotic stressed conditions. These endophytes have the potential to alleviate different stresses by improving crops/plants growth, development, biomass, and photosynthetic and other physiological traits. The beneficial role of the endophytes may be attributed to stress-modulating enzymes such as the antioxidants SOD, POD and APX and ACC deaminases. Additionally, the higher production of different classes of bioactive secondary metabolites, i.e., flavonoids, proline, and glutathione may also overcome tissue damage to plants under stressed conditions. Interestingly, a number of medicinally important phytochemicals such as anhydropseudo-phlegmcin-9, 10-quinone-3-amino-8-O methyl ether 'anhydropseudophlegmacin-9, 10-quinone-3-amino-8-Omethyl ether were reported from the endophytic flora of P. hysterophorus. Moreover, various reports revealed that fungal and bacterial endophytes of P. hysterophorus enhance plant growth-promoting attributes and could be added to the consortium of biofertilizers.

A Study on the Anti-NF-кB, Anti-Candida, and Antioxidant Activities of Two Natural Plant Hormones: Gibberellin A4 and A7

Introduction: Gibberellins (GA) are terpenoids that serve as important plant hormones by acting as growth and response modulators against injuries and parasitism. In this study, we investigated the in vitro anti-NF-κB, anti-Candida, and antioxidant activity of gibberellin A4 (GA4) and A7 (GA7) compounds, and further determined their toxicity in vivo. Methods: GA4 and GA7 in vitro toxicity was determined by MTT method, and nontoxic concentrations were then tested to evaluate the GA4 and GA7 anti-NF-κB activity in LPS-activated RAW-luc macrophage cell culture (luminescence assay). GA4 in silico anti-NF-κB activity was evaluated by molecular docking with the software “AutoDock Vina”, “MGLTools”, “Pymol”, and “LigPlot+”, based on data obtained from “The Uniprot database”, “Protein Data Bank”, and “PubChem database”. The GA4 and GA7 in vitro anti-Candida effects against Candida albicans (MYA 2876) were determined (MIC and MFC). GA7 was also evaluated regarding the viability of C. albicans preformed biofilm (microplate assay). In vitro antioxidant activity of GA4 and GA7 was evaluated against peroxyl radicals, superoxide anions, hypochlorous acid, and reactive nitrogen species. GA4 and GA7 in vivo toxicity was determined on the invertebrate Galleria mellonella larvae model. Results: Our data show that GA4 at 30 µM is nontoxic and capable of reducing 32% of the NF-κB activation on RAW-luc macrophages in vitro. In vitro results were confirmed via molecular docking assay (in silico), since GA4 presented binding affinity to NF-κB p65 and p50 subunits. GA7 did not present anti-NF-κB effects, but exhibited anti-Candida activity with low MIC (94 mM) and MFC (188 mM) values. GA7 also presented antibiofilm properties at 940 mM concentration. GA4 did not present anti-Candida effects. Moreover, GA4 and GA7 showed antioxidant activity against peroxyl radicals, but did not show scavenging activity against the other tested radicals. Both compounds did not affect the survival of G. mellonella larvae, even at extremely high doses (10 g/Kg). Conclusion: Our study provides preclinical evidence indicating that GA4 and GA7 have a favorable low toxicity profile. The study also points to GA4 and GA7 interference with the NF-κB via, anti-Candida activity, and a peroxyl radical scavenger, which we argue are relevant biological effects.

Influence of Cynara cardunculus L. Phenolic Compounds on Pseudomonas putida Isolated from the Dairy Industry: Growth and Melanin Bioproduction

Cynara cardunculus L. inflorescence infusion has been used for several centuries as curd in traditional cheese making, such as some highly prized Portuguese cheeses. To promote the sustainable use of all C. cardunculus plants, C. cardunculus extract leaves decoction (CL), inflorescence decoction (CI), chlorogenic acid (CA) (a compound in the plant leaves), and rosmarinic acid (RA) (a similar phenolic compound) solutions were tested for antimicrobial activity against bacteria that may appear on the cheese rind. The antimicrobial activity was evaluated by 15 bacterial strains using two different methodologies: solid and liquid. The influence of these extracts and the phenolic compounds on melanin bioproduction by Pseudomonas putida ESACB 191 was also studied. CA and RA (1 mg/mL) showed antimicrobial activity. CL and CA reduced P. putida ESACB 191 growth in the liquid assay and melanin bioproduction by 6.20 Log CFU/mL and 50%, respectively. Cynarin, CA, and its derivates were identified as the main phenolic compounds (52%) of CL, which may justify its inhibitory action on bacterial growth and melanin bioproduction. Thus, future perspectives include the application of CL extracts with antimicrobial activity in edible films and/or coatings to applied in cheese rind to increase the shelf time.

Phytochemical and Nutritional Profile Composition in Fruits of Different Sweet Chestnut (Castanea sativa Mill.) Cultivars Grown in Romania

Chestnut (Castanea sativa Mill.), a valuable fruit crop, is cultivated in small areas in Romania, mostly in the west, where the moderate continental climate has a slight Mediterranean influence. This work aims to investigate the bioactive characteristics (total polyphenols, total flavonoids and antioxidant activity), individual polyphenolic composition, phytochemical and nutritional HRMS screening profiles, sugar and mineral composition of six sweet chestnut cultivars, namely ‘Marsol’, ‘Maraval’, ‘Bournette’, ‘Précoce Migoule’ and ‘Marissard’ grown at Fruit Growing Research—Extension Station (SCDP) Vâlcea, in Northern Oltenia, Romania. Fruit samples were collected in two consecutive years, in order to study the impact of genetic variability between cultivars and the influence of the different climatic conditions corresponding to different cultivation years. Principal Component Analysis (PCA) and Hierarchical Cluster Analysis (HCA) allow the discrimination between the sweet chestnut fruits harvested in different years and different sweet chestnut cultivars. Analytical investigations revealed that sweet chestnut cultivars grown in Romania show similar bioactive, phytochemical and nutritional composition to cultivars grown in the large European chestnut-producing countries, indicating the high adaptation potential of the chestnut in the temperate continental zone with small Mediterranean influences characteristic of the southwestern area of Romania.