Biochemical Properties and Catalytic Specificity of a Novel Neutral Serine Peptidase Secreted by Fungus Pyrenochaetopsis sp

Changes in the urinary proteome of rats after short-term intake of magnesium L-threonate(MgT)

Introduction

Magnesium (Mg) is an important mineral in living organisms. Magnesium has multiple functions in the human body, wherein it plays an important therapeutic and preventive role in a variety of diseases.

Methods

Urine samples of rats before and after gavage of magnesium L-threonate (MgT) were collected, and the urinary proteome was identified using the LC-MS/MS technique and analyzed using various databases.

Results and discussion

The results illustrated that the urinary proteome of rats was significantly altered after short-term intake of magnesium supplements and that the differential proteins and the biological functions were related to magnesium. This study innovatively establishes a method to study nutrients from the perspective of urine proteomics. This work demonstrates that the urinary proteome is capable of reflecting the effects of nutrient intake on the organism in a more systematic and comprehensive manner and has the potential to provide clues for clinical nutrition research and practice.

Wheat Straw Return Influences Soybean Root-Associated Bacterial and Fungal Microbiota in a Wheat-Soybean Rotation System

Roots hold complex microbial communities at the soil–root interface, which can affect plant nutrition, growth, and health. Although the composition of plant microbiomes has been extensively described for various plant species and environments, little is known about the effect of wheat straw return (WSR) on the soybean root microbiota. We used Illumina-based 16S rRNA and ITS amplicon sequencing to track changes in bacterial and fungal microbiota in bulk soil and soybean rhizosphere, rhizoplane, s1and endosphere during the third and fourth years after implementing WSR in a wheat–soybean rotation system. The results revealed that WSR had a greater impact on fungal communities than bacterial communities, particularly in bulk soil, rhizosphere, and rhizoplane. WSR enriched the relative abundance of cellulose-degrading fungi (e.g., Acremonium, Trichoderma, and Myrmecridium, among which Trichoderma also had antimicrobial activity), saprotroph (e.g., Exophiala), and nitrogen cycling bacteria (e.g., Chryseolinea). Furthermore, WSR depleted the relative abundance of pathogenic fungi (e.g., Fusarium and Alternaria). These data revealed for the first time that WSR had diverse effects on soybean root-associated microbial community composition, not only in soil but also in the rhizosphere, rhizoplane, and endosphere.

Application of Feature-Based Molecular Networking for Comparative Metabolomics and Targeted Isolation of Stereoisomers from Algicolous Fungi

Seaweed endophytic (algicolous) fungi are talented producers of bioactive natural products. We have previously isolated two strains of the endophytic fungus, Pyrenochaetopsis sp. FVE-001 and FVE-087, from the thalli of the brown alga Fucus vesiculosus. Initial chemical studies yielded four new decalinoylspirotetramic acid derivatives with antimelanoma activity, namely pyrenosetins A-C (1-3) from Pyrenochaetopsis sp. strain FVE-001, and pyrenosetin D (4) from strain FVE-087. In this study, we applied a comparative metabolomics study employing HRMS/MS based feature-based molecular networking (FB MN) on both Pyrenochaetopsis strains. A higher chemical capacity in production of decalin derivatives was observed in Pyrenochaetopsis sp. FVE-087. Notably, several decalins showed different retention times despite the same MS data and MS/MS fragmentation pattern with the previously isolated pyrenosetins, indicating they may be their stereoisomers. FB MN-based targeted isolation studies coupled with antimelanoma activity testing on the strain FVE-087 afforded two new stereoisomers, pyrenosetins E (5) and F (6). Extensive NMR spectroscopy including DFT computational studies, HR-ESIMS, and Mosher's ester method were used in the structure elucidation of compounds 5 and 6. The 3'R,5'R stereochemistry determined for compound 6 was identical to that previously reported for pyrenosetin C (3), whose stereochemistry was revised as 3'S,5'R in this study. Pyrenosetin E (5) inhibited the growth of human malignant melanoma cells (A-375) with an IC50 value of 40.9 μM, while 6 was inactive. This study points out significant variations in the chemical repertoire of two closely related fungal strains and the versatility of FB MN in identification and targeted isolation of stereoisomers. It also confirms that the little-known fungal genus Pyrenochaetopsis is a prolific source of complex decalinoylspirotetramic acid derivatives.

Protease Produced by Endophytic Fungi: A Systematic Review

The purpose of this systematic review was to identify the available literature of production, purification, and characterization of proteases by endophytic fungi. There are few complete studies that entirely exhibit the production, characterization, and purification of proteases from endophytic fungi. This study followed the PRISMA, and the search was conducted on five databases: PubMed, PMC, Science Direct, Scopus Articles, and Web of Science up until 18 May 2021, with no time or language restrictions. The methodology of the selected studies was evaluated using GRADE. Protease production, optimization, purification, and characterization were the main evaluated outcomes. Of the 5540 initially gathered studies, 15 met the inclusion criteria after a two-step selection process. Only two studies optimized the protease production using statistical design and two reported enzyme purification and characterization. The genus Penicillium and Aspergillus were the most cited among the eleven different genera of endophytic fungi evaluated in the selected articles. Six studies proved the ability of some endophytic fungi to produce fibrinolytic proteases, demonstrating that endophytic fungi can be exploited for the further production of agents used in thrombolytic therapy. However, further characterization and physicochemical studies are required to evaluate the real potential of endophytic fungi as sources of industrial enzymes.

Mycobiota Associated with the Vascular Wilt of Poplar

In 2017, a 560-ha area of hybrid poplar plantation in northern Poland showed symptoms of tree decline. The leaves appeared smaller, yellow-brown, and were shed prematurely. Twigs and smaller branches died without distinct cankers. Trunks decayed from the base. The phloem and xylem showed brown necrosis. Ten percent of the trees died 1–2 months after the first appearance of the symptoms. None of these symptoms were typical for known poplar diseases. The trees’ mycobiota were analysed using Illumina sequencing. A total of 69 467 and 70 218 operational taxonomic units (OTUs) were obtained from the soil and wood. Blastocladiomycota and Chytridiomycota occurred only in the soil, with very low frequencies (0.005% and 0.008%). Two taxa of Glomeromycota, with frequencies of 0.001%, occurred in the wood. In the soil and wood, the frequencies of Zygomycota were 3.631% and 0.006%, the frequencies of Ascomycota were 45.299% and 68.697%, and the frequencies of Basidiomycota were 4.119% and 2.076%. At least 400 taxa of fungi were present. The identifiable Zygomycota, Ascomycota, and Basidiomycota were represented by at least 18, 263 and 81 taxa, respectively. Many fungi were common to the soil and wood, but 160 taxa occurred only in soil and 73 occurred only in wood. The root pathogens included species of Oomycota. The vascular and parenchymal pathogens included species of Ascomycota and of Basidiomycota. The initial endophytic character of the fungi is emphasized. Soil, and possibly planting material, may be the sources of the pathogen inoculum, and climate warming is likely to be a predisposing factor. A water deficit may increase the trees’ susceptibility. The epidemiology of poplar vascular wilt reminds grapevine trunk diseases (GTD), including esca, black foot disease and Petri disease.

Evaluation of the milk clotting properties of an aspartic peptidase secreted by Rhizopus microsporus

Traditionally, chymosin has been used for milk-clotting, but this naturally occurring enzyme is in short supply and its use has raised religious and ethical concerns. Because milk-clotting peptidases are a promising substitute for chymosin in cheese preparation, there is a need to find and test the specificity of these enzymes. Here, we evaluated the milk-clotting properties of an aspartic peptidase secreted by Rhizopus microsporus. The molecular mass of this enzyme was estimated at 36 kDa and Pepstatin A was determined to be an inhibitor. Optimal activity occurred at a pH of 5.5 and a temperature range of 50-60 °C, but the peptidase was stable in the pH range of 4-7 and a temperature as low as 45 °C. Proteolytic activity was significantly reduced in the presence of Cu²⁺ and Al³⁺. When enzyme substrates based on FRET were used, this peptidase exhibited the highest catalytic efficiency for Abz-KNRSSKQ-EDDnp (4,644 ± 155 mM^-1.s^-1), Abz-KLRSSNQ-EDDnp (3,514 ± 130 mM^-1.s^-1), and Abz-KLRQSKQ-EDDnp (3,068 ± 386 mM^-1.s^-1). This study presents a promising peptidase for use in cheese making, due to its high stability in the presence of Ca²⁺ and broad pH range of 4-7, in addition to its ability to efficiently clot milk.