Purification and characterization of antifungal phenazines from a fluorescent Pseudomonas strain FPO4 against medically important fungi

Recent Advances in Phenazine Natural Products: Biosynthesis and Metabolic Engineering

Phenazine natural products are a class of nitrogen-containing heterocyclic compounds produced by microorganisms. The tricyclic ring molecules show various chemical structures and extensive pharmacological activities, such as antimicrobial, anticancer, antiparasitic, anti-inflammatory, and insecticidal activities, with low toxicity to the environment. Since phenazine-1-carboxylic acid has been developed as a registered biopesticide, the application of phenazine natural products will be promising in the field of agriculture pathogenic fungi control based on broad-spectrum antifungal activity, minimal toxicity to the environment, and improvement of crop production. Currently, there are still plenty of intriguing hidden biosynthetic pathways of phenazine natural products to be discovered, and the titer of naturally occurring phenazine natural products is insufficient for agricultural applications. In this review, we spotlight the progress regarding biosynthesis and metabolic engineering research of phenazine natural products in the past decade. The review provides useful insights concerning phenazine natural products production and more clues on new phenazine derivatives biosynthesis.

Genome analysis of Pseudomonas strain 4B with broad antagonistic activity against toxigenic fungi

Pseudomonas sp. 4B isolated from the effluent pond of a bovine abattoir was investigated as antifungal against toxigenic fungi. The complete genome of Pseudomonas 4B was sequenced using the Illumina MiSeq platform. Phylogenetic analysis and genome comparisons indicated that the strain belongs to the Pseudomonas aeruginosa group. In silico investigation revealed gene clusters associated with the biosynthesis of several antifungals, including pyocyanin, rhizomide, thanamycin, and pyochelin. This bacterium was investigated through antifungal assays, showing an inhibitory effect against all toxigenic fungi tested. Bacterial cells reduced the diameter of fungal colonies, colony growth rate, and sporulation of each indicator fungi in 10-day simultaneous growing tests. The co-incubation of bacterial suspension and fungal spores in yeast extract-sucrose broth for 48 h resulted in reduced spore germination. During simultaneous growth, decreased production of aflatoxin B1 and ochratoxin A by Aspergillus flavus and Aspergillus carbonarius, respectively, was observed. Genome analysis and in vitro studies showed the ability of P. aeruginosa 4B to reduce fungal growth parameters and mycotoxin levels, indicating the potential of this bacterium to control toxigenic fungi. The broad antifungal activity of this strain may represent a sustainable alternative for the exploration and subsequent use of its possible metabolites in order to control mycotoxin-producing fungi.

Electro-Oxidative Synthesis of Phenazines

We disclose herein electro-oxidative synthesis as the general protocol for procuring phenazines under mild reaction conditions. Using aerial oxygen as an oxidant, inexpensive electrolyte, and electrodes, a diverse range of phenazines have been accessed in good yields via the ring contraction of 10,11-dihydro-5H-dibenzo[b,e][1,4]diazepines. In addition, the syntheses of phenazines and diamino phenazines via direct electro-oxidation of dihydrophenazines and electro-dimerization of o-phenylenediamines, respectively, have also been accomplished.

Recent Developments in the Biological Activities, Bioproduction, and Applications of Pseudomonas spp. Phenazines

Phenazines are a large group of heterocyclic nitrogen-containing compounds with demonstrated insecticidal, antimicrobial, antiparasitic, and anticancer activities. These natural compounds are synthesized by several microorganisms originating from diverse habitats, including marine and terrestrial sources. The most well-studied producers belong to the Pseudomonas genus, which has been extensively investigated over the years for its ability to synthesize phenazines. This review is focused on the research performed on pseudomonads' phenazines in recent years. Their biosynthetic pathways, mechanism of regulation, production processes, bioactivities, and applications are revised in this manuscript.

Advances in Phenazines over the Past Decade: Review of Their Pharmacological Activities, Mechanisms of Action, Biosynthetic Pathways and Synthetic Strategies

Phenazines are a large group of nitrogen-containing heterocycles, providing diverse chemical structures and various biological activities. Natural phenazines are mainly isolated from marine and terrestrial microorganisms. So far, more than 100 different natural compounds and over 6000 synthetic derivatives have been found and investigated. Many phenazines show great pharmacological activity in various fields, such as antimicrobial, antiparasitic, neuroprotective, insecticidal, anti-inflammatory and anticancer activity. Researchers continued to investigate these compounds and hope to develop them as medicines. Cimmino et al. published a significant review about anticancer activity of phenazines, containing articles from 2000 to 2011. Here, we mainly summarize articles from 2012 to 2021. According to sources of compounds, phenazines were categorized into natural phenazines and synthetic phenazine derivatives in this review. Their pharmacological activities, mechanisms of action, biosynthetic pathways and synthetic strategies were summarized. These may provide guidance for the investigation on phenazines in the future.

Phenazine 1-carboxylic acid Producing Seed Harbored Endophytic Bacteria from Cultivated Rice Variety of Kerala and Its Broad Range Antagonism to Diverse Plant Pathogens

Endophytic microorganisms residing within the diverse parts of plants play a significant role in the plant growth and defense response. In the case of the vertically transmitted seed-borne endophytes, they form the promising initiator of the juvenile plant microbiome by supporting the growth and establishment of the seedlings. Hence, the current study emphasizes the isolation and screening of plant beneficial traits of seed endophytes from the cultivated rice variety Jyothi of Kerala, India. Among the 14 bacterial endophytes obtained in the study, the isolate S3 was found to have promising activity against the phytopathogens such as Fusarium oxysporum, Pythium aphanidermatum, Pythium myriotylum, Phytophthora infestans, Rhizoctonia solani, Colletotrichum acutatum, and Sclerotium rolfsii. The isolate S3 was further identified as Paenibacillus polymyxa by the 16S rRNA-based sequence analysis. Furthermore, the isolate was confirmed for its capability for hydrogen cyanide (HCN) production, 1-aminocyclopropane-1-carboxylate (ACC) deaminase activity, biofilm formation, and nitrogen fixation. The P. polymyxa S3 was also found to have the potential to provide post-harvest protection to the rice kernels from Sclerotium rolfsii. By the LC-MS/MS analysis, the organism was confirmed for the production of phenazine 1-carboxylic acid which could be the prime chemical basis of its antifungal activity. The in vivo plant growth evaluation has also demonstrated the root length enhancement effect of P. polymyxa S3 in Vigna unguiculata. Here, the root length of P. polymyxa S3-treated plant was enhanced to 12.44 ± 0.58223 cm when compared with distilled water control (10.261 ± 0.38151 cm) and the observed change was statistically significant as per the analysis of variance at P value less than 0.05. Based on all these properties, the isolated P. polymyxa S3 could be considered as a promising agent to be used for the development of competent plant probiotic formulations.

Chemical Constituents and Biological Activities of Croton heliotropiifolius Kunth

Croton heliotropiifolius Kunth (Euphorbiaceae), whose occurrence has already been registered in the most varied Brazilian biomes, is commonly found in the Chapada do Araripe, Ceará. The species is traditionally used to treat fungal, parasitic, and degenerative diseases. This study investigated the chemical composition and pharmacological potential (antioxidant, antifungal, antiparasitic, and cytotoxic) of an aqueous extract obtained from the roots of C. heliotropiifolius. Following a qualitative phytochemical screening, the chemical constituents were identified by ultra-efficiency liquid chromatography coupled witha quadrupole/time-of-flight system (UPLC-QTOF). The antioxidant potential was verified by thin-layer chromatography (TLC). The direct and combined antifungal activity of the extract against opportunistic Candida strains was investigated using the microdilution method. The minimal fungicidal concentration (MFC) was determined by subculture, while the modulation of the morphological transition (fungal virulence) was evaluated by light microscopy. The in vitro antiparasitic activity was analyzed using epimastigotes of Trypanosoma cruzi and promastigotes of Leishmania braziliensis and Leishmania infantum, while cytotoxicity was determined in cultures of mouse fibroblasts. The phytochemical analysis identified the presence of acids, terpenes, flavonoids, lignans, and alkaloids. Among these constituents, the presence of polar and non-polar phenolic compounds with known antioxidant action was highlighted. While the extract showed clinically ineffective antifungal effects, it could enhance the effectiveness of fluconazole, in addition to inhibiting the morphological transition associated with increased virulence in Candida strains. Although the extract showed low cytotoxicity against fibroblasts, it also had weak antiparasitic effects. In conclusion, Croton heliotropiifolius is a source of natural products with antifungal and antioxidant potential.

Elucidation and Identification of an Antifungal Compound from Pseudomonas aeruginosa DA3.1 Isolated from Soil in Vietnam

Background: Fusarium sp. and Rhizoctonia sp. fungi have been always threats to short-term crops. In Vietnam, corn and soybean suffer serious losses annually. Therefore, it is necessary to utilize an environmentally friendly antifungal compound that is highly effective against phytopathogenic fungi. Pseudomonas sp. is a popular soil bacterial strain and well known for its high antifungal activity. Objectives: This study was carried out to evaluate and assess the antifungal activity of a local bacterial strain namely DA3.1 that was later identified as Pseudomonas aeruginosa. This would be strong scientific evidence to develop an environmentally friendly biocide from a local microorganism strain for commercial use. Methods: The antifungal compound was purified from ethyl acetate extraction of deproteinized cell culture broth by a silica gel column (CH2Cl2/MeOH (0% - 10% MeOH)). The purity of the isolated compound was determined by HPLC, and its molecular structure was elucidated using spectroscopic experiments including one-dimensional (1D) (1H NMR, 13C NMR, DEPT) and two-dimensional (2D) (HMBC and HSQC) spectra. The activity of the purified compound against Fusarium sp. and Rhizoctonia sp. fungi was measured using the PDA-disk diffusion method, and its growth-promoting ability was evaluated using the seed germination test of corn and soybean. Results: The results showed that the antifungal compound produced by Pseudomonas aeruginosa DA3.1 had a retention factor (Rf) of 0.86 on thin layer chromatography (TLC). Based on the evidence of spectral data including proton nuclear magnetic resonance (1H NMR), carbon nuclear magnetic resonance (13C NMR), distortionless enhancement by polarization transfer (DEPT), heteronuclear multiple bond correlation (HMBC), and heteronuclear single quantum coherence (HSQC), the chemical structure was elucidated as phenazine-1-carboxylic. The purified compound showed inhibitory activity against F. oxysporum and R. solani and exhibited the ability of the germination of corn and soybean seeds. The results revealed the benefit of native P. aeruginosa DA3.1 and phenazine-1-carboxylic acid for use as a biocontrol agent, as well as a plant growth promoter. Conclusions: The antifungal compound isolated from local Pseudomonas DA3.1 was identified as phenazine-1-carboxylic acid that posed high antifungal activity and was a plant germination booster.

Aspergillus-Pseudomonas interaction, relevant to competition in airways

In airways of immunocompromised patients and individuals with cystic fibrosis, Pseudomonas aeruginosa and Aspergillus fumigatus are the most common opportunistic bacterial and fungal pathogens. Both pathogens form biofilms and cause acute and chronic illnesses. Previous studies revealed that P. aeruginosa is able to inhibit A. fumigatus biofilms in vitro. While numerous P. aeruginosa molecules have been shown to affect A. fumigatus, there never has been a systematic approach to define the principal causative agent. We studied 24 P. aeruginosa mutants, with deletions in genes important for virulence, iron acquisition, or quorum sensing, for their ability to interfere with A. fumigatus biofilms. Cells, planktonic or biofilm culture filtrates of four P. aeruginosa mutants, pvdD-pchE-, pvdD-, lasR-rhlR-, and lasR-, inhibited A. fumigatus biofilm metabolism or planktonic A. fumigatus growth significantly less than P. aeruginosa wild type. The common defect of these four mutants was a lack in the production of the P. aeruginosa siderophore pyoverdine. Pure pyoverdine affected A. fumigatus biofilm metabolism, and restored inhibition by the above mutants. In lungs from cystic fibrosis patients, pyoverdine production and antifungal activity correlated. The key inhibitory mechanism for pyoverdine was iron-chelation and denial of iron to A. fumigatus. Further experiments revealed a counteracting, self-protective mechanism by A. fumigatus, based on A. fumigatus siderophore production.

Metabolic engineering strategies for enhanced shikimate biosynthesis: current scenario and future developments

Shikimic acid is an important intermediate for the manufacture of the antiviral drug oseltamivir (Tamiflu®) and many other pharmaceutical compounds. Much of its existing supply is obtained from the seeds of Chinese star anise (Illicium verum). Nevertheless, plants cannot supply a stable source of affordable shikimate along with laborious and cost-expensive extraction and purification process. Microbial biosynthesis of shikimate through metabolic engineering and synthetic biology approaches represents a sustainable, cost-efficient, and environmentally friendly route than plant-based methods. Metabolic engineering allows elevated shikimate production titer by inactivating the competing pathways, increasing intracellular level of key precursors, and overexpressing rate-limiting enzymes. The development of synthetic and systems biology-based novel technologies have revealed a new roadmap for the construction of high shikimate-producing strains. This review elaborates the enhanced biosynthesis of shikimate by utilizing an array of traditional metabolic engineering along with novel advanced technologies. The first part of the review is focused on the mechanistic pathway for shikimate production, use of recombinant and engineered strains, improving metabolic flux through the shikimate pathway, chemically inducible chromosomal evolution, and bioprocess engineering strategies. The second part discusses a variety of industrially pertinent compounds derived from shikimate with special reference to aromatic amino acids and phenazine compound, and main engineering strategies for their production in diverse bacterial strains. Towards the end, the work is wrapped up with concluding remarks and future considerations.

Studies of Pseudomonas aeruginosa Mutants Indicate Pyoverdine as the Central Factor in Inhibition of Aspergillus fumigatus Biofilm

Pseudomonas aeruginosa and Aspergillus fumigatus are common opportunistic bacterial and fungal pathogens, respectively. They often coexist in airways of immunocompromised patients and individuals with cystic fibrosis, where they form biofilms and cause acute and chronic illnesses. Hence, the interactions between them have long been of interest and it is known that P. aeruginosa can inhibit A. fumigatusin vitro We have approached the definition of the inhibitory P. aeruginosa molecules by studying 24 P. aeruginosa mutants with various virulence genes deleted for the ability to inhibit A. fumigatus biofilms. The ability of P. aeruginosa cells or their extracellular products produced during planktonic or biofilm growth to affect A. fumigatus biofilm metabolism or planktonic A. fumigatus growth was studied in agar and liquid assays using conidia or hyphae. Four mutants, the pvdD pchE, pvdD, lasR rhlR, and lasR mutants, were shown to be defective in various assays. This suggested the P. aeruginosa siderophore pyoverdine as the key inhibitory molecule, although additional quorum sensing-regulated factors likely contribute to the deficiency of the latter two mutants. Studies of pure pyoverdine substantiated these conclusions and included the restoration of inhibition by the pyoverdine deletion mutants. A correlation between the concentration of pyoverdine produced and antifungal activity was also observed in clinical P. aeruginosa isolates derived from lungs of cystic fibrosis patients. The key inhibitory mechanism of pyoverdine was chelation of iron and denial of iron to A. fumigatusIMPORTANCE Interactions between human pathogens found in the same body locale are of vast interest. These interactions could result in exacerbation or amelioration of diseases. The bacterium Pseudomonas aeruginosa affects the growth of the fungus Aspergillus fumigatus Both pathogens form biofilms that are resistant to therapeutic drugs and host immunity. P. aeruginosa and A. fumigatus biofilms are found in vivo, e.g., in the lungs of cystic fibrosis patients. Studying 24 P. aeruginosa mutants, we identified pyoverdine as the major anti-A. fumigatus compound produced by P. aeruginosa Pyoverdine captures iron from the environment, thus depriving A. fumigatus of a nutrient essential for its growth and metabolism. We show how microbes of different kingdoms compete for essential resources. Iron deprivation could be a therapeutic approach to the control of pathogen growth.

A genetic screen in combination with biochemical analysis in Saccharomyces cerevisiae indicates that phenazine-1-carboxylic acid is harmful to vesicular trafficking and autophagy

The environmentally friendly antibiotic phenazine-1-carboxylic acid (PCA) protects plants, mammals and humans effectively against various fungal pathogens. However, the mechanism by which PCA inhibits or kills fungal pathogens is not fully understood. We analyzed the effects of PCA on the growth of two fungal model organisms, Saccharomyces cerevisiae and Candida albicans, and found that PCA inhibited yeast growth in a dose-dependent manner which was inversely dependent on pH. In contrast, the commonly used antibiotic hygromycin B acted in a dose-dependent manner as pH increased. We then screened a yeast mutant library to identify genes whose mutation or deletion conferred resistance or sensitivity to PCA. We isolated 193 PCA-resistant or PCA-sensitive mutants in clusters, including vesicle-trafficking- and autophagy-defective mutants. Further analysis showed that unlike hygromycin B, PCA significantly altered intracellular vesicular trafficking under growth conditions and blocked autophagy under starvation conditions. These results suggest that PCA inhibits or kills pathogenic fungi in a complex way, in part by disrupting vesicular trafficking and autophagy.

Pharmacological Potential of Phylogenetically Diverse Actinobacteria Isolated from Deep-Sea Coral Ecosystems of the Submarine Avilés Canyon in the Cantabrian Sea

Marine Actinobacteria are emerging as an unexplored source for natural product discovery. Eighty-seven deep-sea coral reef invertebrates were collected during an oceanographic expedition at the submarine Avilés Canyon (Asturias, Spain) in a range of 1500 to 4700 m depth. From these, 18 cultivable bioactive Actinobacteria were isolated, mainly from corals, phylum Cnidaria, and some specimens of phyla Echinodermata, Porifera, Annelida, Arthropoda, Mollusca and Sipuncula. As determined by 16S rRNA sequencing and phylogenetic analyses, all isolates belong to the phylum Actinobacteria, mainly to the Streptomyces genus and also to Micromonospora, Pseudonocardia and Myceligenerans. Production of bioactive compounds of pharmacological interest was investigated by high-performance liquid chromatography (HPLC) and gas chromatography-mass spectrometry (GC-MS) techniques and subsequent database comparison. Results reveal that deep-sea isolated Actinobacteria display a wide repertoire of secondary metabolite production with a high chemical diversity. Most identified products (both diffusible and volatiles) are known by their contrasted antibiotic or antitumor activities. Bioassays with ethyl acetate extracts from isolates displayed strong antibiotic activities against a panel of important resistant clinical pathogens, including Gram-positive and Gram-negative bacteria, as well as fungi, all of them isolated at two main hospitals (HUCA and Cabueñes) from the same geographical region. The identity of the active extracts components of these producing Actinobacteria is currently being investigated, given its potential for the discovery of pharmaceuticals and other products of biotechnological interest.

Are There Any Other Compounds Isolated From Dermacoccus spp at All?

Microbial-derived natural products have functional and structural diversity and complexity. For several decades, they have provided the basic foundation for most drugs available to modern medicine. Microbial-derived natural products have wide-ranging applications, especially as chemotherapeutics for various diseases and disorders. By exploring distinct microorganisms in different environments, small novel bioactive molecules with unique functionalities and biological or biomedical significance can be identified. Aquatic environments, such as oceans or seas, are considered to be sources of abundant novel bioactive compounds. Studies on marine microorganisms have revealed that several bioactive compounds extracted from marine algae and invertebrates are eventually generated by their associated bacteria. These findings have prompted intense research interest in discovering novel compounds from marine microorganisms. Natural products derived from Dermacoccus exhibit antibacterial, antitumor, antifungal, antioxidant, antiviral, antiparasitic, and eventually immunosuppressive bioactivities. In this review, we discussed the diversity of secondary metabolites generated by genus Dermacoccus with respect to their chemical structure, biological activity, and origin. This brief review highlights and showcases the pivotal importance of Dermacoccus-derived natural products and sheds light on the potential venues of discovery of new bioactive compounds from marine microorganisms.

Pyocyanin as anti-tyrosinase and anti tinea corporis: A novel treatment study

OBJECTIVE

The aim of this study was to evaluate the efficiency of pyocyanin pigment as a novel compound active against tyrosinase with its depigmentation efficiency for combating Trichophyton rubrum which could be a major causative agent of tinea corporis.

METHODS

Fifty swabs of fungal tinea corporis infections were collected and identified. Five MDRPA isolates were tested for their levels of pyocyanin production. The purified extracted pyocyanin was characterized by UV spectrum and FT-IR analysis. Pyocyanin activity against tyrosinase was determined by dopachrome micro-plate. In addition, the antidermatophytic activity of pyocyanin against T. rubrum was detected by radial growth technique. In vivo novel trial was conducted to evaluate the efficiency and safety of pyocyanin as an alternative natural therapeutic compound against T. rubrum causing tinea corporis.

RESULTS

Purified pyocyanin showed highly significant inhibitory activity against tyrosinase and T. rubrum. In vivo topical treatments with pyocyanin ointment revealed the efficiency of pyocyanin (MIC 2000 μg/ml) to cure tinea corporis compared to fluconazole, which showed a partial curing at a higher concentration (MIC 3500 μg/ml) after two weeks of treatment. In addition, the results revealed complete healing and disappear of hyperpigmentation by testing the safety of pyocyanin ointment and its histopathological efficiency in the skin treatment without any significant toxic effect.

CONCLUSION

Pyocyanin pigment could be a promising anti-tyrosinase and a new active compound against T. rubrum, which could be a major causative agent of tinea corporis. In fact, if pyocyanin secondary metabolite is going to be used in practical medication, it will support the continuous demand of novel antimycotic natural agents against troublesome fungal infections.