Fungi present distinguishable isotopic signals in their lipids when grown on glycolytic versus tricarboxylic acid cycle intermediates
<p>Microbial activity in soils controls both the size and turnover rates of large carbon (<span class="inline-formula">C</span>) inventories stored in the subsurface, having important consequences for partitioning of <span class="inline-formula">C</span...
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| Main Authors: | , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2025-07-01
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| Series: | Biogeosciences |
| Online Access: | https://bg.copernicus.org/articles/22/3127/2025/bg-22-3127-2025.pdf |
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| Summary: | <p>Microbial activity in soils controls both the size and turnover rates of large carbon (<span class="inline-formula">C</span>) inventories stored in the subsurface, having important consequences for partitioning of <span class="inline-formula">C</span> between terrestrial and atmospheric reservoirs as well as recycling of mineral nutrients such as nitrogen or phosphorus (often bound to the <span class="inline-formula">C</span>) that support plant growth. Fungi are major decomposers of soil organic matter (SOM); however, uncertainty about the identity of predominant <span class="inline-formula">C</span> substrates that fuel their respiration confound models of fungal production and SOM turnover. To further define the signals of microbial heterotrophic activity, we applied a dual hydrogen (<span class="inline-formula">H</span>) and <span class="inline-formula">C</span> stable isotope probing (SIP) approach to pure fungal cultures representing the phyla Ascomycota, Basidiomycota, and Zygomycota growing on monomeric (glucose, succinate) or complex substrates (tannic acid, <span class="inline-formula"><i>β</i></span>-cyclodextrin). Our findings demonstrate that the investigated species incorporated only minor quantities of inorganic <span class="inline-formula">C</span> (provided as bicarbonate) into their membrane lipids, amounting to <span class="inline-formula"><</span> 3 % of lipid-C, with no consistent patterns observed between species or growth substrates. The net incorporation of water-derived <span class="inline-formula">H</span> (i.e., <span class="inline-formula"><i>a</i><sub>w</sub></span>) into lipids also did not differ significantly between incubations with monomeric versus complex substrates; however, growth on succinate elicited significantly higher <span class="inline-formula"><i>a</i><sub>w</sub></span> values than glucose or <span class="inline-formula"><i>β</i></span>-cyclodextrin. This finding suggests that <span class="inline-formula"><sup>2</sup>H-SIP</span> assays have the potential to distinguish between microbial communities supported predominantly by substrates that are catabolized by the tricarboxylic acid cycle versus glycolytic pathway. Furthermore, the average <span class="inline-formula"><i>a</i><sub>w</sub></span> value of heterotrophic fungal incubations 0.69 <span class="inline-formula">±</span> 0.03 (SEM) is consistent with that observed for bacterial heterotrophs and may be applied for upscaling lipid-based estimates of fungal production in environmental assays.</p> |
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| ISSN: | 1726-4170 1726-4189 |