Physiological stress tolerance responses of the dung decomposer fungus Mucor circinelloides

The Mucor circinelloides complex, a group of dung-dwelling fungi, is essential for nutrient cycling and organic matter breakdown. Despite their ecological significance, variations in germination rates and stress tolerance among isolates are not well understood. This study examined four isolates—Cicarelli, Doc Beaver, Papulsa, and Zaina—to assess their germination on various media, including potato dextrose agar (PDA), Czapek (CZA), Sabouraud dextrose agar (SDA), Emerson (EM), and minimal media (MM). The results showed notable differences in germination rates, with CZA and EM promoting the fastest growth. The study also analysed sporangiospore tolerance to UV-B radiation and high temperatures (47 °C), with findings highlighting the role of growth media in stress resistance. Sporangiospores from Cicarelli, Doc Beaver, and Papulsa grown on PDA exhibited greater UV-B tolerance than those on CZA. Conversely, sporangiospores produced on CZA were more heat tolerant than those on PDA. The 12-h survival curve for the Zaina isolate reinforced these findings, showing similar trends in UV-B resilience and heat tolerance. This research demonstrates how growth media influence the environmental stress responses in M. circinelloides, providing insights into the adaptive potential of these fungi.