Fungal secondary metabolite gliotoxin enhances enzymatic activity in soils by reshaping their microbiome

Gliotoxin (GT) is a sulfur-containing epidithiodioxopiperazine produced by various filamentous fungi, including those used in biological plant protection (Trichoderma virens). The pronounced antimicrobial effect of GT on a variety of fungi and bacteria makes it a promising agent for controlling phytopathogens in agricultural systems. In this study, we aim to investigate the microbiological properties of the soil microbiome after the introduction of GT. GT was applied at doses of 10, 25, 50, 100 and 500 μM kg⁻¹ soil. Soil sampling was carried out after 1, 7, 14, 30, 60 and 90 days of incubation. It was found that GT significantly stimulated the respiratory activity of soil microorganisms and maintained this activity throughout the experiment. Carbon of microbial biomass, on the contrary, decreases under the influence of GT and is restored at the end of the experiment only in microcosms with 10 and 25 μM GT. Separate estimates of bacterial and fungal biomass showed that the bacterial community increased in biomass on day 14, while fungal biomass increased on day 30 after the treatment. Under the influence of GT, the activity of soil enzymes involved in the carbon (CB, βG, βX), nitrogen (NAG, LAP) and phosphate (AP) cycles significantly increased. High-throughput amplicon sequencing of the ITS and 16S rDNA markers revealed that the soil fungal community is more susceptible to GT than the bacterial community. This was reflected in changes in alpha-diversity indices and in the pattern of changes in the abundance of some microbial genera. Thus, on the one hand, the data obtained provides insight into the biological effects of GT on the soil microbial community. On the other hand, it sets the direction for further research into the ecological role of antibiotics produced by soil and rhizosphere microorganisms.