Biodiversity and chitinase production of soil fungi in the Cerrado biome of Minas Gerais

Abstract

The Brazilian Cerrado is the second largest biome in the country and extends mainly across the central region of Brazil, harboring an exuberant biodiversity of plants and animals. However, this biome has already lost more than 44% of its native vegetation as a result of land-use change for the production of grains, such as soybeans, corn, and coffee, in addition to meat production. The impact of land-use change on the fungal communities of the Cerrado is still poorly understood, as is the diversity of these microorganisms and their enzymatic potential. Thus, the main objectives of this study were to investigate and compare fungal diversity in soils under different land uses, including agricultural areas of regenerative and conventional coffee cultivation, and areas of native Cerrado vegetation, in the municipality of Patrocínio, Minas Gerais. In addition, the study aimed to test the chitinolytic potential and to identify, through polyphasic taxonomy, fungal isolates obtained from the soil of these three different land-use systems. The serial dilution technique was used to isolate a total of 1.481 fungal strains from 60 soil samples. Aliquots of 0.1 mL of the dilutions were transferred to standardized culture media, Dichloran Rose Bengal Chloramphenicol (DRBC) and Dichloran Glycerol 18% (DG18), incubated at 25 °C for 7 days. Through Next-Generation Sequencing (NGS), soil samples from native Cerrado showed significant differences in both alpha and beta diversities; the native Cerrado areas Ce1 and Ce2 presented the lowest alpha diversity among the analyzed areas (Chao1 consistently < 50). However, fungal groups were similar among Cerrado samples, with a higher relative abundance of the phylum Basidiomycota, genera Apiotrichum and Saitozyma. On the other hand, coffee cultivation areas, both conventional and regenerative, presented similar fungal groups belonging to the phylum Ascomycota. Regarding chitinase production, the highest number of fungal strains with activity above 70 U min−1 was isolated from conventional coffee soil, suggesting that the type of management may influence the synthesis of this enzyme. Seven new species of the genus Penicillium were described: P. patrocinensis (section Brevicompacta), P. guarae (section Cinnamopurpurea), P. seriamae (section Guizhouorum), P. beraoi and P. moreirae (section Lanata-Divaricata), P. pequii and P. pluvialis (section Ramosum). Other isolates were identified as occurrence records of 29 species. Of this total, four were identified using partial sequences of the BenA, CaM, and RPB2 genes, while the remaining 25 were identified only through the partial sequence of the BenA gene. These results reinforce that land-use change exerts a strong impact on the fungal communities of the Cerrado. Furthermore, they demonstrate that this biome constitutes an important reservoir of new species, whose diversity presents high potential for biotechnological applications, especially in the production of hydrolytic enzymes such as chitinases.