Arsenault Emily R, Liew Jia Huan, Hopkins Jacob R
Kansas Biological Survey and Department of Ecology and Evolutionary Biology, University of Kansas, Lawrence, KS, USA.
Program in Environmental Studies, Bates College, Lewiston, ME, USA.
Environ Microbiol. 2022 Apr;24(4):2089-2097. doi: 10.1111/1462-2920.15961. Epub 2022 Mar 8.
Fungi link detrital resources and metazoan consumers through their role as decomposers. However, fungal contributions to metazoans may be misestimated in amino acid isotope studies because fungi are capable of both synthesizing amino acids (AAs) de novo and absorbing AAs from their environment. While fungi cultured in AA-free media have been used to represent fungi in studies of natural environments, fungi likely gain energetic benefits by taking up substrate AAs directly in situ. Consequently, fungi cultured on AA-free media may not be representative of the true variability of natural fungal δ C profiles. Therefore, the objective of this experiment was to determine the effect of substrate AA availability on yeast δ C profiles. We found that yeasts cultured in media of relatively higher AA content had different δ C profiles than yeasts grown in AA-free media, in part because yeasts utilized two essential AAs (Leu and Val) directly from media substrates when available in sufficient amounts. Furthermore, these differences among yeast δ C profiles remained after normalization of δ C values. We recommend further characterization of the variation in fungal δ C profiles and the incorporation of this potential variability into interpretations of basal resource use by metazoans.
真菌作为分解者，将碎屑资源与后生动物消费者联系起来。然而，在氨基酸同位素研究中，真菌对后生动物的贡献可能被错误估计，因为真菌既能从头合成氨基酸（AAs），也能从环境中吸收氨基酸。虽然在无氨基酸培养基中培养的真菌已被用于在自然环境研究中代表真菌，但真菌可能通过在原位直接摄取底物氨基酸而获得能量益处。因此，在无氨基酸培养基上培养的真菌可能无法代表天然真菌δC谱的真正变异性。因此，本实验的目的是确定底物氨基酸可用性对酵母δC谱的影响。我们发现，在氨基酸含量相对较高的培养基中培养的酵母与在无氨基酸培养基中生长的酵母具有不同的δC谱，部分原因是当有足够量的两种必需氨基酸（亮氨酸和缬氨酸）时，酵母会直接从培养基底物中利用它们。此外，在δC值标准化后，酵母δC谱之间的这些差异仍然存在。我们建议进一步表征真菌δC谱的变化，并将这种潜在的变异性纳入对后生动物基础资源利用的解释中。
