Transcriptome and Metabolome Integration Reveals the Impact of Fungal Elicitors on Triterpene Accumulation in Sanghuangporus sanghuang.

Sanghuangporus sanghuang is a large wood-decaying mushroom highly valued in traditional Chinese medicine due to its medicinal properties, including hypoglycemic, antioxidant, antitumor, and antibacterial properties effects. Its key bioactive compounds include flavonoids and triterpenoids. Specific fungal genes can be selectively induced by fungal elicitors. To investigate the effect of fungal polysaccharides derived from Perenniporia tenuis mycelia on the metabolites of S. sanghuang, we conducted metabolic and transcriptional profiling with and without elicitor treatment (ET and WET, respectively). Correlation analysis showed significant differences in triterpenoid biosynthesis between the ET and WET groups. In addition, the structural genes associated with triterpenoids and their metabolites in both groups were verified using quantitative real-time polymerase chain reaction (qRT-PCR) and high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). Through metabolite screening, three triterpenoids were identified: betulinol, betulinic acid, and 2-hydroxyoleanolic acid. Excitation treatment increased the level of betulinic acid by 2.62-fold and 2-hydroxyoleanolic acid by 114.67-fold compared to WET. The qRT-PCR results of the four genes expressed in secondary metabolic pathways, defense gene activation, and signal transduction showed significant variation between the ET and WET groups. Overall, our study suggests that the fungal elicitor induced the aggregation of pentacyclic triterpenoid secondary metabolites in S. sanghuang.

Comparative transcriptome analysis reveals multiple functions for Mhy1p in lipid biosynthesis in the oleaginous yeast Yarrowia lipolytica.

Yarrowia lipolytica is considered as a promising microbial cell factory for bio-oil production due to its ability to accumulate a large amount of lipid. However, the regulation of lipid metabolism in this oleaginous yeast is elusive. In this study, the MHY1 gene was disrupted, and 43.1% (w/w) intracellular oil based on cell dry weight was obtained from the disruptant M-MHY1, while only 30.2% (w/w) lipid based on cell dry weight was obtained from the reference strain. RNA-seq was then performed to analyze transcriptional changes during lipid biosynthesis after MHY1 gene inactivation. The expression of 1597 genes, accounting for 24.7% of annotated Y. lipolytica genes, changed significantly in the disruptant M-MHY1 during lipid biosynthesis. Differential gene expression analysis indicated that Mhy1p performs multiple functions and participates in a wide variety of biological processes, including lipid, amino acid and nitrogen metabolism. Notably, data analysis revealed increased carbon flux through lipid biosynthesis following MHY1 gene inactivation, accompanied by decreased carbon flux through amino acid biosynthesis. Moreover, Mhy1p regulates the cell cycle, and the cell cycle rate was enhanced in the disruptant M-MHY1. These results suggest that Mhy1p plays critical regulatory roles in diverse aspects of various biological processes, especially in lipid biosynthesis, amino acid and nitrogen metabolism and cell cycle. Our dataset appears to elucidate the crucial role of Mhy1p in lipid biosynthesis and serves as a resource for exploring physiological dimorphic growth in Y. lipolytica.

Microbial community and metabolic pathway succession driven by changed nutrient inputs in tailings: effects of different nutrients on tailing remediation.

To solve the competition problem of acidophilic bacteria and sulfate-reducing bacteria in the practical application of mine tailing bioremediation, research into the mechanisms of using different nutrients to adjust the microbial community was conducted. Competition experiments involving acidophilic bacteria and sulfate-reducing bacteria were performed by supplementing the media with yeast extract, tryptone, lactate, and glucose. The physiochemical properties were determined, and the microbial community structure and biomass were investigated using MiSeq sequencing and qRT-PCR, respectively. Four nutrients had different remediation mechanisms and yielded different remediation effects. Yeast extract and tryptone (more than 1.6 g/L) promoted sulfate-reducing bacteria and inhibited acidophilic bacteria. Lactate inhibited both sulfate-reducing and acidophilic bacteria. Glucose promoted acidophilic bacteria more than sulfate-reducing bacteria. Yeast extract was the best choice for adjusting the microbial community and bioremediation, followed by tryptone. Lactate kept the physiochemical properties stable or made slight improvements; however, glucose was not suitable for mine tailing remediation. Different nutrients had significant effects on the abundance of the second enzyme of the sulfate-reducing pathway (p < 0.05), which is the rate-limiting step of sulfate-reducing pathways. Nutrients changed the remediation effects effectively by adjusting the microbial community and the abundance of the sulfate-reducing rate-limiting enzyme.

High-Level Production of Exopolysaccharides by a Cosmic Radiation-Induced Mutant M270 of the Maitake Medicinal Mushroom, Grifola frondosa (Agaricomycetes).

A new Grifola frondosa mutant, M270, was successfully isolated for high production of exopolysaccharides (EPSs) using cosmic radiation-induced mutagenesis. We found that the mutant M270 had a clearer and thicker EPS layer (~10 µm) adhering to mycelia than those of its parent strain 265 after Congo red staining. In the 20-L batch fermentation for M270, 10.3 g/L of EPS and 17.9 g/L of dry mycelia biomass were obtained after 204 hours of fermentation. Furthermore, a main water-soluble fraction (EP1) in the EPS was purified from M270 and then confirmed to be heteroglycan-protein complex with 91% (w/w) total carbohydrates and 9% (w/w) total proteins. Four kinds of monosaccharide-D-mannose, D-glucosamine, D-glucose, and D-xylose-were detected in EP1 with a molar ratio of 17.6:1.8:100:2.5. The molecular mass of the main component in EP1 was 8.9 kDa. The EPS from M270 significantly inhibited the growth of sarcoma 180 solid tumors in mice. This G. frondosa M270 mutant could serve as a better candidate strain for polysaccharide production.