Regulation of fungal decomposition at single-cell level

Abstract

Filamentous fungi play a key role as decomposers in Earth's nutrient cycles. In soils, substrates are heterogeneously distributed in microenvironments. Hence, individual hyphae of a mycelium may experience very different environmental conditions simultaneously. In the current work, we investigated how fungi cope with local environmental variations at single-cell level. We developed a method based on infrared spectroscopy that allows the direct, in-situ chemical imaging of the decomposition activity of individual hyphal tips. Colonies of the ectomycorrhizal Basidiomycete Paxillus involutus were grown on liquid media, while parts of colonies were allowed to colonize lignin patches. Oxidative decomposition of lignin by individual hyphae growing under different conditions was followed for a period of seven days. We identified two subpopulations of hyphal tips: one with low decomposition activity and one with much higher activity. Active cells secreted more extracellular polymeric substances and oxidized lignin more strongly. The ratio of active to inactive hyphae strongly depended on the environmental conditions in lignin patches, but was further mediated by the decomposition activity of entire mycelia. Phenotypic heterogeneity occurring between genetically identical hyphal tips may be an important strategy for filamentous fungi to cope with heterogeneous and constantly changing soil environments.

Seeking the Roles for Fungal Small-Secreted Proteins in Affecting Saprophytic Lifestyles

“…In spite of widespread cytoplasmic continuity present in many filamentous fungi, both environmental changes as well as inherent developmental factors can confer phenotypic heterogeneity along different sections of an integral colony (Tegelaar and Wösten, 2017;Op De Beeck et al, 2020;Tegelaar et al, 2020). Is it possible that SSPs are "self-effectors", which are involved in the regulation of the mentioned heterogeneity?…”

OCTAVVS: A Graphical Toolbox for High-Throughput Preprocessing and Analysis of Vibrational Spectroscopy Imaging Data

“…The usefulness of the OCTAVVS MCR-ALS analysis tool for enhancing spectra and highlighting spectral changes was demonstrated on a set of 96 images, part of a larger study on the regulation of degradation processes in the ectomycorrhizal fungus Paxillus involutus. In that study, the MCR-ALS-ROI functionality was used to remove contaminated areas, and cluster annotation was performed to extract comparable spectra from all images [27].…”

OCTAVVS: A graphical toolbox for high-throughput preprocessing and analysis of vibrational spectroscopy imaging data

“…The usefulness of the OCTAVVS MCR-ALS analysis tool for enhancing spectra and highlighting spectral changes was demonstrated on a set of 96 images, part of a larger study on the regulation of degradation processes in the ectomycorrhizal fungus Paxillus involutus. In that study, the MCR-ALS-ROI functionality was used to remove contaminated areas, and cluster annotation was performed to extract comparable spectra from all images [23].…”

“…The software and new algorithms were validated on spectra from experiments where thin films of organic material (lignin) were colonized by the ectomycorrhizal fungus Paxillus involutus, as described in a separate publication [23]. Images of fungal hyphae were recorded during 8 days of growth, under two slightly different growth conditions (with/without Fe 3+ in the lignin film), each with six replicates.…”

“…Right: MCR-ALS analysis and clustering steps, using the preprocessed data as input and ending in the extraction of average spectra for three identified regions of the image. Example data from a fungal cell grown on lignin[23]. Rectangles represent data (sharp corners) or processing steps (rounded corners).…”