Antibacterial activities of penicillic acid isolated from Aspergillus persii against various plant pathogenic bacteria

Antimicrobial and Cytotoxic Activities of the Secondary Metabolites of Endophytic Fungi Isolated from the Medicinal Plant Hyssopus officinalis

According to the World Health Organization, it is estimated that by 2050, drug-resistant infections could cause up to 10 million deaths annually. Therefore, finding a new generation of antibiotics is crucial. Natural compounds from endophytic fungi are considered a potential source of new-generation antibiotics. The antimicrobial and cytotoxic effects of ethyl acetate extracts of nine endophytic fungal isolates obtained from Hyssopus officinalis were investigated for bioassay-guided isolation of the natural compounds. An extract of isolate VII showed the highest antimicrobial activities against Gram-positive bacteria Bacillus subtilis and Staphylococcus aureus (30.12 ± 0.20 mm and 35.21 ± 0.20 mm) and Gram-negative bacteria Escherichia coli and Pseudomonas aeruginosa (30.41 ± 0.23 mm and 25.12 ± 0.25 mm) among the tested extracts of isolates. Molecular identification of isolate VII confirmed it as Chaetomium elatum based on sequencing of its ITS genes, and it was discovered that this was the first time C. elatum had been isolated from H. officinalis. This isolate was cultured at a large scale for the isolation and identification of the active compound. Penicillic acid was isolated for the first time from C. elatum and its chemical structure was established by NMR spectroscopy. The penicillic acid showed strong antibacterial activities against Bacillus subtilis and Staphylococcus aureus with 20.68 mm and 25.51 mm inhibition zones, respectively. In addition, MIC and MBC values and antibiofilm activities of penicillic acid were determined. It was found that penicillic acid reduced the level of biofilms in proportion to antibacterial activity.

Polyketides as Secondary Metabolites from the Genus Aspergillus

Polyketides are an important class of structurally diverse natural products derived from a precursor molecule consisting of a chain of alternating ketone and methylene groups. These compounds have attracted the worldwide attention of pharmaceutical researchers since they are endowed with a wide array of biological properties. As one of the most common filamentous fungi in nature, Aspergillus spp. is well known as an excellent producer of polyketide compounds with therapeutic potential. By extensive literature search and data analysis, this review comprehensively summarizes Aspergillus-derived polyketides for the first time, regarding their occurrences, chemical structures and bioactivities as well as biosynthetic logics.

Biological Control Potential of Penicillium brasilianum against Fire Blight Disease

Erwinia amylovora is a causative pathogen of fire blight disease, affecting apple, pear, and other rosaceous plants. Currently, management of fire blight relies on cultural and chemical practices, whereas it has been known that few biological resources exhibit disease control efficacy against the fire blight. In the current study, we found that an SFC20201208-M01 fungal isolate exhibits antibacterial activity against E. amylovora TS3128, and the isolate was identified as a Penicillium brasilianum based on the β-tubulin (BenA) gene sequence. To identify active compounds from the P. brasilianum culture, the culture filtrate was partitioned with ethyl acetate and n-butanol sequentially. From the ethyl acetate layer, we identified two new compounds (compounds 3-4) and two known compounds (compounds 1-2) based on spectroscopic analyses and comparison with literature data. Of these active compounds, penicillic acid (1) exhibited promising antibacterial activity against E. amylovora TS3128 with a minimal inhibitory concentration value of 25 μg/ml. When culture filtrate and penicillic acid (125 μg/ml) were applied onto Chinese pearleaf crab apple seedlings prior to inoculation of E. amylovora TS3128, the development of fire blight disease was effectively suppressed in the treated plants. Our results provide new insight into the biocontrol potential of P. brasilianum SFC20201208-M01 with an active ingredient to control fire blight.

Isolation and agricultural potential of penicillic acid against citrus canker

AIMS

The control of Xanthomonas citri subsp. citri (X. citri), causal agent of citrus canker, relies heavily in integrated agricultural practices involving the use of copper-based chemicals. Considering the need for alternatives to control this disease and the potential of fungi from extreme regions as producers of bioactive metabolites, we isolated and identified a bioactive compound from Penicillium sp. CRM 1540 isolated from Antarctica marine sediment.

METHODS AND RESULTS

The compound potential as an antibacterial agent against X. citri was assessed through in vitro and greenhouse experiments. Molecular taxonomy indicates this fungus is a possible new species of Penicillium. The results revealed 90% inhibition at 25 µg mL^-1 in vitro and a decrease in symptoms emergency for the in vivo experiment in Citrus sinensis (L.) Osbeck leaves. The number of lesions per cm² for the treatment with the isolated compound was 75.31% smaller and significantly different (p <0.05) from the untreated control. The structure of the active agent was identified as penicillic acid based on detailed spectroscopic analysis.

CONCLUSION

Penicillic acid can be an alternative against citrus canker.

SIGNIFICANCE AND IMPACT OF STUDY

Research on extremophile microorganisms can lead to molecules with biotechnological potential and alternatives to current agriculture practices.

In Vitro Antibacterial, Antifungal, Nematocidal and Growth Promoting Activities of Trichoderma hamatum FB10 and Its Secondary Metabolites

Microbial natural biocides have attracted much more attention in recent years in order to avoid the unrestricted use of chemical biocides in the environment. The aim of this study is to analyze the antibacterial and antifungal activities of secondary metabolites and growth promoting, nematicidal, and soil enzyme activity mediated by Trichoderma hamatum FB10. The bactericidal and fungicidal activities were performed using cell-free extract. Results revealed that the selected strain exert antibacterial activity against Acidovorax avenae, Erutimacarafavora, and Xanthomonas campestris. The selected fungal strain FB10 showed antagonistic activity against fungal pathogens such as, S. sclerotiorum, Rhizoctonia solani, Alternaria radicina, Alternaria citri, and Alternaria dauci. Among the bacterial pathogens, A. avenae showed least MIC (30 ± 2.5 µg/mL) and MBC (70 ± 1.25 µg/mL) values. T. hamatum FB10 strain synthesized bioactive volatile secondary metabolite, which effectively inhibited the growth of bacteria and fungi and indicated the presence of 6-pentyl-alpha-pyrone as the major compound (67.05%). The secondary metabolite synthesized by T. hamatum FB10 showed nematicidal activity against M. incognita eggs. Egg hatch inhibition was 78 ± 2.6% and juvenile stage mortality rate was 89 ± 2.5% when the strain FB10 was treated with nematode. The cell free extract of T. hamatum FB10 showed protease, amylase, cellulase, chitinase, glucanase activities. T. hamatum FB10 inoculated with green gram increased 11% plant height, compared to the control. The fresh weight of the experimental group inoculated with T. hamatum FB10 increased 33.6% more compared to the control group. The green gram seedlings inoculated with T. hamatum FB10 increased 18% more dry weight than control group. Soil enzymes such as, urease, phosphatase, catalase and saccharase were improved in the soil inoculated with T. hamatum FB10. These biochemical components play potent role in soil fertility, energy conversion, and in soil organic matter conversion.

Chemoinformatic Screening for the Selection of Potential Senolytic Compounds from Natural Products

Cellular senescence is a cellular condition that involves significant changes in gene expression and the arrest of cell proliferation. Recently, it has been suggested in experimental models that the elimination of senescent cells with pharmacological methods delays, prevents, and improves multiple adverse outcomes related to age. In this sense, the so-called senoylitic compounds are a class of drugs that selectively eliminates senescent cells (SCs) and that could be used in order to delay such adverse outcomes. Interestingly, the first senolytic drug (navitoclax) was discovered by using chemoinformatic and network analyses. Thus, in the present study, we searched for novel senolytic compounds through the use of chemoinformatic tools (fingerprinting and network pharmacology) over different chemical databases (InflamNat and BIOFACQUIM) coming from natural products (NPs) that have proven to be quite remarkable for drug development. As a result of screening, we obtained three molecules (hinokitiol, preussomerin C, and tanshinone I) that could be considered senolytic compound candidates since they share similarities in structure with senolytic leads (tunicamycin, ginsenoside Rb1, ABT 737, rapamycin, navitoclax, timosaponin A-III, digoxin, roxithromycin, and azithromycin) and targets involved in senescence pathways with potential use in the treatment of age-related diseases.

Antibiotics from Extremophilic Micromycetes

Extremophilic microorganisms, which are capable of functioning normally at extremely high or low temperatures, pressure, and in other environmental conditions, have been in the focus of microbiologists' attention for several decades due to the biotechnological potential of enzymes inherent in extremophiles. These enzymes (also called extremozymes) are used in the production of food and detergents and other industries. At the same time, the inhabitants of extreme econiches remained almost unexplored for a long time in terms of the chemistry of natural compounds. In recent years, the emergence of new antibiotic-resistant strains of pathogens, which affect humans and animals has become a global problem. The problem is compounded by a strong slowdown in the development of new antibiotics. In search of new active substances and scaffolds for medical chemistry, researchers turn to unexplored natural sources. In recent years, there has been a sharp increase in the number of studies on secondary metabolites produced by extremophiles. From the discovery of penicillin to the present day, micromycetes, along with actinobacteria, are one of the most productive sources of antibiotic compounds for medicine and agriculture. Many authors consider extremophilic micromycetes as a promising source of small molecules with an unusual mechanism of action or significant structural novelty. This review summarizes the latest (for 2018-2019) experimental data on antibiotic compounds, which are produced by extremophilic micromycetes with various types of adaptation. Active metabolites are classified by the type of structure and biosynthetic origin. The data on the biological activity of the isolated metabolites are summarized.

Overview on antibacterial metabolites from terrestrial Aspergillus spp

Medicines developed from natural sources are a frequent target for the research and discovery of antimicrobial compounds. Discovering of penicillin in 1928 was a motive to explore of nature as a source of new antimicrobial agents. Fungi produce a diverse range of bioactive metabolites, making them rich source of different types of medicines. The purpose of this paper was to review studies on antibacterials from terrestrial Aspergillus published exclusively during 1942-2018, with emphasis on their antibacterial activities, structures, and mechanisms of action if present. According to the results from different studies in the world, large number of compounds and extracts showed different activities against different bacterial species, including Gram-positive and Gram-negative bacteria. The most prominent result was that of the compound CJ-17,665, isolated from A. ochraceus, showing good activity against multi-drug resistant Staphylococcus aureus, which is well-recognised to be one of the most important current public health problem. These findings may motivate scientists to undertake a project that may result in the development of novel antibacterial drugs from terrestrial-derived Aspergillus spp., although further toxicity assays (in vivo) must be performed before their application.

Antimicrobial activities of an oxygenated cyclohexanone derivative isolated from Amphirosellinia nigrospora JS-1675 against various plant pathogenic bacteria and fungi

AIMS

To evaluate the antimicrobial activities of an active compound isolated from the culture broth of Amphirosellinia nigrospora JS-1675 against various plant pathogenic bacteria and fungi.

METHODS AND RESULTS

While screening for bioactive secondary metabolites from endophytic fungi, we found that A. nigrospora JS-1675 showed strong in vitro antibacterial activity against Ralstonia solanacearum. One compound (1) was isolated and identified as (4S, 5S, 6S)-5,6-epoxy-4-hydroxy-3-methoxy-5-methyl-cyclohex-2-en-1-one. Growth of most of the tested phytopathogenic bacteria was inhibited by compound 1 and the ethyl acetate (EtOAc) layer except Pseudomonas syringae pv. lachrymans. Compound 1 also inhibited the mycelial growth of several plant pathogenic fungi. Both compound 1 and the EtOAc layer reduced bacterial leaf spot disease in detached peach leaves. They also suppressed the development of bacterial wilt on tomato seedlings quite effectively.

CONCLUSIONS

Amphirosellinia nigrospora JS-1675 showed antimicrobial activity against plant pathogenic bacteria and fungi by producing compound 1.

SIGNIFICANCE AND IMPACT OF THE STUDY

This is the first report on the occurrence of compound 1 in A. nigrospora JS-1675 and its efficacy against plant pathogenic bacteria and fungi. Their strong disease control efficacy against tomato bacterial wilt suggests that this fungus can be used as a microbial bactericide.

Draft Genome Sequence of Aspergillus persii NIBRFGC000004109, Which Has Antibacterial Activity against Plant-Pathogenic Bacteria

The fungus Aspergillus persii strain NIBRFGC000004109 is capable of producing penicillic acid and showed antibacterial activity against various plant-pathogenic bacteria, including Xanthomonas arboricola pv. pruni. Here, we report the first draft whole-genome sequence of A. persii. The assembly comprises 38,414,373 bp, with 12 scaffolds.

Microbial taxa and functional genes shift in degraded soil with bacterial wilt

Soil degradation is a serious global problem, but little is known about how soil microbial communities respond to soil degradation as well as their feedback to ecosystem functioning. In this study, we found the microbial community composition, structure and functional potential significantly altered in the degraded soils with bacterial wilt (termed as degraded soils). Compared with healthy soils, OTU richness of beneficial microorganisms were significantly decreased, but OTU richness of pathogenic microorganisms were significantly increased in the degraded soils. Functional gene array (GeoChip 5.0) analysis showed the functional metabolic potential of genes involved in stress, virulence, sulfur cycle, metal resistance, degradation of plant cell wall was significantly increased in the degraded soils. Increased functional metabolic potential of these genes may be related to the acidification and severe plant disease of degraded soils. Biological activity of degraded soils was obviously decreased with weakened soil enzyme activities when compared to the healthy soils. Soil pH and enzyme activities were negatively correlated with the abundance of genes involved in sulfur cycle, virulence, and stress responses. This study provides new insights into our understanding of soil microbial community responses to soil degradation.