Inhibition of Phenolics Uptake by Ligninolytic Fungal Cells and Its Potential as a Tool for the Production of Lignin-Derived Aromatic Building Blocks

Genome-Wide Identification of the ABC Gene Family and Its Expression in Response to the Wood Degradation of Poplar in Trametes gibbosa

Wood-rotting fungi's degradation of wood not only facilitates the eco-friendly treatment of organic materials, decreasing environmental pollution, but also supplies crucial components for producing biomass energy, thereby reducing dependence on fossil fuels. The ABC gene family, widely distributed in wood-rotting fungi, plays a crucial role in the metabolism of lignin, cellulose, and hemicellulose. Trametes gibbosa, as a representative species of wood-rotting fungi, exhibits robust capabilities in wood degradation. To investigate the function of the ABC gene family in wood degradation by T. gibbosa, we conducted a genome-wide analysis of T. gibbosa's ABC gene family. We identified a total of 12 Tg-ABCs classified into four subfamilies (ABCA, ABCB, ABCC, and ABCG). These subfamilies likely play significant roles in wood degradation. Scaffold localization and collinearity analysis results show that Tg-ABCs are dispersed on scaffolds and there is no duplication of gene sequences in the Tg-ABCs in the genome sequence of T. gibbosa. Phylogenetic and collinearity analyses of T. gibbosa along with four other wood-rotting fungi show that T. gibbosa shares a closer phylogenetic relationship with its same-genus fungus (Trametes versicolor), followed by Ganoderma leucocontextum, Laetiporus sulphureus, and Phlebia centrifuga in descending order of phylogenetic proximity. In addition, we conducted quantitative analyses of Tg-ABCs from T. gibbosa cultivated in both woody and non-woody environments for 10, 15, 20, 25, 30, and 35 days using an RT-qPCR analysis. The results reveal a significant difference in the expression levels of Tg-ABCs between woody and non-woody environments, suggesting an active involvement of the ABC gene family in wood degradation. During the wood degradation period of T. gibbosa, spanning from 10 to 35 days, the relative expression levels of most Tg-ABCs exhibited a trend of increasing, decreasing, and then increasing again. Additionally, at 20 and 35 days of wood degradation by T. gibbosa, the relative expression levels of Tg-ABCs peak, suggesting that at these time points, Tg-ABCs exert the most significant impact on the degradation of poplar wood by T. gibbosa. This study systematically reveals the biological characteristics of the ABC gene family in T. gibbosa and their response to woody environments. It establishes the foundation for a more profound comprehension of the wood-degradation mechanism of the ABC gene family and provides strong support for the development of more efficient wood-degradation strategies.

A compartmentalized microsystem helps understanding the uptake of benzo[a]pyrene by fungi during soil bioremediation processes

Hydrophobic organic soil contaminants such as polycyclic aromatic hydrocarbons (PAH) are poorly mobile in the aqueous phase and tend to sorb to the soil matrix, resulting in low bioavailability. Some filamentous fungi are efficient in degrading this kind of pollutants. However, the mechanism of mobilization of hydrophobic compounds by non-motile microorganisms such as filamentous fungi needs investigations to improve pollutant bioavailability and bioremediation efficiency. Usual homogeneous media for microbial growth in the lab are poorly suited to model the soil, which is a compartmentalized and heterogeneous habitat. A microfluidic device was designed to implement a compartmentalization of the fungal inoculum and the source of the pollutant benzo[a]pyrene (BaP) as a deposit of solid crystals in order to gain a further insight into the mechanisms involved in the access to the contaminant and its uptake in soils. Thus in this device, two chambers are connected by an array of parallel microchannels that are wide enough to allow individual hyphae to grow through them. Macro-cultures of Talaromyces helicus in direct contact with BaP have shown its uptake and intracellular storage in lipid bodies despite the low propensity of BaP to cross aqueous phases as shown by simulation. Observations of T. helicus in the microfluidic device through laser scanning confocal microscopy indicate preferential uptake of BaP at a close range and through contact with the cell wall. However faint staining of some hyphae before contact with the deposit also suggests an extracellular transport phenomenon. Macro-culture filtrates analyses have shown that T. helicus releases extracellular non-lipidic surface-active compounds able to lower the surface tension of culture filtrates to 49.4 mN/m. Thus, these results highlight the significance of active mechanisms to reach hydrophobic contaminants before their uptake by filamentous fungi in compartmentalized micro-environments and the potential to improve them through biostimulation approaches for soil mycoremediation.