Zhihong Hu

Ergothioneine (EGT) is a rare amino acid with potent antioxidant and anti-inflammatory properties, with a wide range of applications in food, cosmetics, an

Ergosterol is an important component of fungal cell membranes and participates in the regulation of its fluidity, permeability, and material transport. In our study, we found that the ergosterol biosynthesis pathway in Aspergillus oryzae is more complex than that in Saccharomyces cerevisiae , involving 49 enzymes and 25 reactions. In this study, we systematically analyzed the expression pattern and subcellular localization of A. oryzae ergosterol synthases and their effects on ergosterol and fatty acid metabolism. The results showed that ergosterol synthase genes were distributed across the eight chromosomes of the A. oryzae genome and were differentially expressed at different growth times. Subcellular localization analysis revealed that the mevalonate biosynthesis-related enzymes were localized in the cytoplasm, mitochondria, and peroxisomes; farnesyl pyrophosphate biosynthesis-related enzymes were mainly localized in the cytoplasm, peroxisomes, and mitochondria; while several ergosterol biosynthesis-related enzymes were localized in the endoplasmic reticulum and lipid droplets. Overexpression (OE) of these enzymes affected both ergosterol and fatty acid contents in A. oryzae . The ergosterol content was the highest in the AoHmgB -OE strain and the lowest in the AoHmgA -OE strain, while the fatty acid content was the highest in the AoErg26B -OE strain and the lowest in the AoErg26A -OE strain. Moreover, the ergosterol content was significantly increased in the AoHmgB / AoErg7B -, AoHmgB / AoErg9 -, and AoErg1 / AoErg7B -co-OE strains compared to the single gene OE strains. Our study results may offer a scientific foundation for genetic engineering research focusing on lipid metabolism in A. oryzae and related fungi, thereby facilitating the creation of fungal strains with enhanced ergosterol production. IMPORTANCE: Ergosterol, an important fungal cell membrane component, participates in the regulation of membrane fluidity, permeability, and material transport. Previous studies have demonstrated that the ergosterol biosynthesis pathway in Aspergillus oryzae exhibits greater complexity compared to that in Saccharomyces cerevisiae ; nonetheless, research on the ergosterol biosynthesis pathway in A. oryzae remains limited. In this study, we determined the expression pattern and subcellular localization of ergosterol biosynthesis-related enzymes in A. oryzae . Additionally, we assessed the effects of the overexpression (OE) of ergosterol biosynthesis-related genes on ergosterol and fatty acid contents in A. oryzae . Therefore, our study may provide a scientific basis for genetic engineering research on lipid metabolism in A. oryzae and other fungal species.

The use of plant growth-promoting rhizobacteria (PGPR) for the bioremediation of heavy metal cadmium (Cd) and for enhancing plant growth in Cd-polluted soil is widely recognized as an effective approach. This study aimed to isolate Cd-resistant bacteria with plant growth-promoting (PGP) traits from the rhizosphere of vegetables subjected to metal contamination and to investigate the mechanisms associated with Cd adsorption as well as its impact on Cd uptake in lettuce. Six Cd-resistant bacterial strains were isolated from rhizosphere soil, among which the R27 strain exhibited the highest tolerance to Cd (minimum inhibitory concentration of 2000 mg/L) along with PGP traits, including phosphate solubilization (385.11 mg/L), the production of indole-3-acetic acid (IAA) (35.92 mg/L), and siderophore production (3.34 mg/L). Through a range of physiological, biochemical, and molecular assessments, the R27 strain was classified as Bacillus siamensis. This strain demonstrated notable efficiency in removing Cd²⁺ from the growth medium, achieving an efficacy of 80.1%. This removal was facilitated by cell surface adsorption through functional groups such as O–H, C=O, –CO–NH–, and C–O, alongside intracellular Cd accumulation, as evidenced by SEM, TEM, EDX, and FTIR analyses. Pot culture experiments indicated that R27 significantly promoted lettuce seedling growth and helped plants tolerate Cd stress, with the underlying mechanisms likely involving increased antioxidant activities for scavenging reactive oxygen species (ROS) induced by Cd stress, and reduced Cd²⁺ levels in lettuce seedlings to mitigate Cd²⁺ toxicity. These physiological changes were further supported by the down-regulation of genes associated with cadmium transport, including IRT1, Nramp1, HMA2, HMA4, ZIP4, and ZIP12, as well as the significantly reduced root bio-concentration factor (BCF) and translocation factor (TF). In summary, the R27 strain offers considerable potential in the bioremediation of Cd-polluted soils and can serve as a bio-fertilizer to enhance plant growth.

Ergosterol is an important component of fungal cell membrane. Ergosterol biosynthesis involves sterol C-14 reductase, a key enzyme in ergosterol biosynthesis, which has been well studied in Saccharomyces cerevisiae. However, little studies about this important enzyme in Aspergillus oryzae. In this study, two sterol C-14 reductases named AoErg24A and AoErg24B were identified in A. oryzae using bioinformatics analysis. Through phylogenetic tree, expression pattern, subcellular localization, and yeast functional complementation analyses, we discovered that both AoErg24A and AoErg24B are conserved and localized to the endoplasmic reticulum (ER). Both enzymes can partially restore the temperature sensitivity phenotype of a S. cerevisiae erg24 weak mutant. Overexpression of AoErg24A in A. oryzae increased 1.6 times of ergosterol content, while overexpression of AoErg24B led to a slight decrease of ergosterol. Both genes affect the sporulation of A. oryzae. These results uncovered that the two genes function differently in ergosterol biosynthesis. Thus, this study further enhances our understanding of ergosterol biosynthesis in A. oryzae and lays a good foundation for A. oryzae to be used in industrial ergosterol production.

Huan huan Yan, Yi tong Shang, Li hong Wang, Xue qin Tian, Van‑Tuan Tran, Li hua Yao, Bin Zeng, Zhi hong Hu. J. Microbiol. Biotechnol. 2024;34:1-10. https://doi.org/10.4014/jmb.2312.12003

Cordyceps militaris (C. militaris) is a valued medicinal fungus that can be traced back thousands of years in traditional Chinese medicine (TCM). Both TCM and modern scientific research have confirmed the positive effects of C. militaris on human health. In recent years, C. militaris has gained wide popularity; unfortunately, strains often degrade during cultivation, resulting in a decline in fruiting bodies and active components that negatively impacts the development of C. militaris in the health food and medicine industries. This review summarizes the current progresses in research on the genomic, transcriptomic, proteomic, and genetic manipulation of C. militaris and discusses its primary metabolites and strain degradation mechanisms. The current challenges and future prospects of C. militaris research are also discussed.

Sterol 14α-demethylase catalyzes lanosterol hydroxylation, which is one of the key reactions in the biosynthetic pathway of sterols. There is only one sterol 14α-demethylases gene named Erg11 in Saccharomyces cerevisiae genome. In this study, three sterol 14α-demethylases genes named AoErg11A, AoErg11B and AoErg11C were identified in Aspergillus oryzae genome through bioinformatics analysis. The function of these three genes were studied by yeast complementation, and the expression pattern/subcellular localization of these genes/proteins were detected. The results showed that the three AoErg11s were expressed differently at different growth times and under different abiotic stresses. All of the three proteins were located in endoplasmic reticulum. The AoErg11s could not restore the temperature-sensitive phenotype of S. cerevisiae erg11 mutant. Overexpression of the three AoErg11s affected both growth and sporulation, which may be due to the effect of AoErg11s on ergosterol content. Therefore, this study revealed the functions of three AoErg11s and their effects on the growth and ergosterol biosynthesis of A. oryzae, which may contribute to the further understanding of the ergosterol biosynthesis and regulation mechanism in this important filamentous fungus, A. oryzae.

Thiolases, including thioase I and thiolase II, play important roles in lipid metabolism. Aspergillus oryzae , one of the most industrially important filamentous fungi, has been widely used for manufacturing oriental fermented food such as sauce, miso, and sake for a long time. In addition, A. oryzae has a high capability in production of high lipid content and has been used for lipid production.

C. militaris is an insect-born fungus that belongs to Ascomycota and Cordyceps. It has a variety of biological activities that can be applied in medicine, health-care products, cosmeceuticals and other fields. Cordycepin (COR) is one of the major bioactive components identified from C. militaris. Thus, C. militaris and COR have attracted extensive attention. In this study, chemical synthetic methods and the biosynthesis pathway of COR were reviewed. As commercially COR was mainly isolated from C. militaris fermentation, the optimizations for liquid and solid fermentation and genetic modifications of C. militaris to increase COR content were also summarized. Moreover, the research progress of genetic modifications of C. militaris and methods for separation and purification COR were introduced. Finally, the existing problems and future research direction of C. militaris were discussed. This study provides a reference for the production of COR in the future.

Thiolase plays important roles in lipid metabolism. It can be divided into degradative thiolases (Thioase I) and biosynthetic thiolases (thiolases II), which are involved in fatty acid β-oxidation and acetoacetyl-CoA biosynthesis, respectively. The Saccharomyces cerevisiae ( S. cerevisiae ) genome harbors only one gene each for thioase I and thiolase II, namely, Pot1 and Erg10 , respectively. In this study, six thiolases (named AoErg10A−AoErg10F) were identified in Aspergillus oryzae ( A. oryzae ) genome using bioinformatics analysis. Quantitative reverse transcription–PCR (qRT-PCR) indicated that the expression of these six thiolases varied at different growth stages and under different forms of abiotic stress. Subcellular localization analysis showed that AoErg10A was located in the cytoplasm, AoErg10B and AoErg10C in the mitochondria, and AoErg10D-AoErg10F in the peroxisome. Yeast heterologous complementation assays revealed that AoErg10A, AoErg10D, AoErg10E, AoErg10F and cytoplasmic AoErg10B (AoErg10B ^ΔMTS ) recovered the phenotypes of S . cerevisiae erg10 weak and lethal mutants, and that only AoErg10D-F recovered the phenotype of the pot1 mutant that cannot use oleic acid as the carbon source. Overexpression of AoErg10s either affected the growth speed or sporulation of the transgenic strains. In addition, the fatty acid and ergosterol content changed in all the AoErg10-overexpressing strains. This study revealed the function of six thiolases in A. oryzae and their effect on growth, and fatty acid and ergosterol biosynthesis, which may lay the foundation for genetic engineering for lipid metabolism in A. oryzae or other fungi. Importance: Thiolase including thioase I and thiolase II, plays important roles in lipid metabolism. A. oryzae, one of the most industrially important filamentous fungi, has been widely used for manufacturing oriental fermented food such as sauce, miso, and sake for a long time. Besides, A. oryzae has a high capability in production of high lipid content and has been used for lipid production. Thus, it is very important to investiagte the function of thiolases in A. oryzae . In this study, six thiolase (named AoErg10A-AoErg10F) were identified by bioinformatics analysis. Unlike other reported thiolases in fungi, three of the six thiolases showed dual function of thioase I and thiolase II in S. cerevisiae , indicating the lipid metabolism is more complex in A. oryzae . The reveal of founction of these thiolases in A. oryzae can lay the foundation for genetic engineering for lipid metabolism in A. oryzae or other fungi.