The Changes of Chemical Molecular Components in Soil Organic Matter Are Associated with Fungus Mortierella Capitata K.

Fungi play essential roles in the turnover of soil organic matter (SOM). However, it is unclear how fungi affect the chemical molecular composition of SOM. This study examined the effect of saprophytic soil fungus Mortierella capitata K on different soil carbon components and their molecular components. Genome sequencing revealed the ability of the strain to synthesize and degrade heterocycles, heteropolysaccharides, alkenes, terpenoids, steroids, amides, lipids, and amino acids. Subsequently, the turnover of SOM in M. capitata K inoculation with straw (KS) or without straw (K) addition was investigated via an aseptic microcosm experiment for 240 days. Pyrolysis gas chromatography-mass spectrometry analysis (Py-GCMS) showed that the molecular composition of SOM significantly changed with culture time in the two treatments. M. capitata K inoculation increased the relative abundance of tetradecanentitrile, dotriacontane, n-hexadecanoic acid, and n-dodecyl methacrylate in SOM during day 5–180. In contrast, the proportion of components in SOM (oxidizable by potassium permanganate) reduced after M. capitata K inoculation. Similarly, M. capitata K inoculation decreased the relative abundance of alkanes, alkenes, and alcohols in the original SOM on the 240th day. However, the above decline was effectively alleviated after straw addition. Straw addition significantly improved the abundance of n-hexadecanoic acid. RNA sequencing on the 30th day revealed the association between genes encoding alcohol dehydrogenase and SOM ester formation. Therefore, this study may provide insights into the complex feedback loops between microbial activities and molecular composition changes in SOM.