Soil microbial diversity and functional capacity associated with the production of edible mushroom Stropharia rugosoannulata in croplands

Effects of an efficient straw decomposition system mediated by Stropharia rugosoannulata on soil properties and microbial communities in forestland

Cultivation of Stropharia rugosoannulata with straw in forestland is effective for straw biodegradation and can prevent the waste of straw resources and environmental pollution and generate economic benefits. However, there is a lack of systematic evaluation of spent mushroom substrate (SMS) input into forestland, such as soil properties and microbial succession. In this experiment, 0 (CK), 10 (SA), 20 (SB), 30 (SC), 40 (SD), and 50 (SE) kg/m2 straw were used to cultivate S. rugosoannulata, and two soil layers (0-10 cm, 10-20 cm) of the cultivated forestland were analyzed. The results indicated that SMS significantly promoted nutrient accumulation in forestland. The bacterial alpha diversity in the SC treatment group was greater than that in the control and gradually decreased to the control level with interannual changes, while the trend of fungal alpha diversity was opposite to that of bacterial alpha diversity. Furthermore, the SC treatment group positively affected soil nitrogen metabolism-related microorganisms for two consecutive years and significantly promoted tree growth. Habitat niche breadth and null model analysis revealed that bacterial communities were more sensitive than fungal communities after SMS input. Linear mixed model (LMM) analysis revealed that SMS supplementation significantly positively affected bacteria (Gammaproteobacteria and Bacteroidota) and significantly negatively affected fungi (Coniochaetales). The constructed fungal-bacterial co-occurrence networks exhibited modularity, and the five types of bacteria were significantly correlated with soil organic matter (SOM), soil organic carbon (SOC), available potassium (AK), available phosphorus (AAP) and available nitrogen (AN) levels. The structural equation model (SEM) showed that bacterial diversity responded more to changes in soil nutrients than did fungal diversity. Overall, 30 kg/m2 of straw decomposition and 2 years of continuous cultivation were beneficial to soil health. This study provides new insights into the rational decomposition of straw and maintenance of forestland ecological balance by S. rugosoannulata.

A new strategy to improve Ganoderma polysaccharides production by symbiotic fungi elicitors through activating the biosynthetic pathway

Ganoderma lucidum polysaccharides (GLP) attract growing attention due to their remarkable bioactivities, but the low content in raw materials remains a bottleneck severely restricting their application. We previously found a higher polysaccharides accumulation in Ganoderma lucidum cultured in continuous cropping soil, and soil symbiotic fungi are presumed as the key among many factors. Herein, 33 symbiotic fungi were isolated from the soil, and fungal elicitors were prepared to investigate their biotic eliciting effect on GLP biosynthesis. Most elicitors were found to significantly improve GLP production, among which the NO.16 molecularly identified as Penicillium citrinum, exhibited the optimum eliciting effect with GLP yield increasing by 3.4 times. Differences in the biosynthetic pathway genes expressions and the monosaccharide components of GLP were further analyzed. The transcriptions of the main genes of GLP biosynthetic pathway were up-regulated under PCE treatments, suggesting it improves GLP production by activating transcriptions of the biosynthetic pathway genes. Moreover, PCE eliciting significantly altered the monosaccharide compositions of GLP with Gal, Man, GalA, GlcA, and Fuc increasing by 8.17 %, 5.68 %, 5.41 %, 2.66 %, and 1.51 % respectively, but Glc decreased by 23.43 %, which may result in the activity change. It can serve as a new strategy to improve GLP production.