The hypothermic nature of fungi

Abstract

Fungi play essential roles in global health, ecology, and economy, but their thermal biology is relatively unexplored. Mushrooms, the fruiting body of mycelium, were previously noticed to be colder than surrounding air through evaporative cooling. Here, we confirm those observations using infrared thermography and report that this hypothermic state is also observed in mold and yeast colonies. The relatively colder temperature of yeasts and molds is also mediated via evaporative cooling and associated with the accumulation of condensed water droplets on plate lids above colonies. The colonies appear coldest at their center and the surrounding agar appears warmest near the colony edges. The analysis of cultivated Pleurotus ostreatus mushrooms revealed that the hypothermic feature of mushrooms can be observed throughout the whole fruiting process and at the level of mycelium. The mushroom's hymenium was coldest, and different areas of the mushroom appear to dissipate heat differently. We also constructed a mushroom-based air-cooling prototype system capable of passively reducing the temperature of a semiclosed compartment by approximately 10 °C in 25 min. These findings suggest that the fungal kingdom is characteristically cold. Since fungi make up approximately 2% of Earth's biomass, their evapotranspiration may contribute to cooler temperatures in local environments.

Keywords: fungal evapotranspiration; fungal hypothermia; fungal thermoregulation; infrared thermography; mushroom.

Fig. 1.

Wild mushrooms are colder than the surrounding air. Visible images and infrared thermographs of 20 different wild mushrooms in their natural habitat while attached to their natural substrate. (A) Amanita spp.; (B) Pleurotus ostreatus; (C) Amanita muscaria; (D) Amanita brunnescens; (E) Russula spp.; (F) Boletus separans; (G) Russula spp.; (H) Amanita spp.; (I) Thelephora spp.; (J) Cerrena unicolor; (K) Cantharellus spp.; (l) Russula spp.; (M) Hortiboletus spp; (N) Marasmius capillaris; (O) Coprinellus micaceus; (P) Lactifluus spp.; (Q–S) unidentified; and (T) Pleurotus ostreatus. Temperature scale bars at the bottom of each thermograph depict °C. The average temperatures of specimens and surroundings are listed in SI Appendix, Table S1.

Fig. 2.

Yeast and mold colonies are colder than surrounding agar. Visible images and infrared thermograph examples of fungal colonies from (A) C. neoformans H99; (B) C. neoformans cap59 acapsular mutant; (C) C. neoformans B3501; (D) E. dermatitidis; (E) C. albicans; (F) C. tropicalis; (G) C. glabrata; (H) C. auris; (I) C. krusei (J) Candida haemulonii, (K) Candida duobushaemulonii, (L) Saccharomyces cerevisiae, (M) Rhodotorula mucilaginosa, (N) Gliocephalotrichum simplex, (O) Cladosporium sphaerospermum, (P) Penicillium spp., (Q) Aspergillus niger, and (R) Cryomyces antarcticus colonies. Temperature scale bars correspond to group panels A to I, J to O, and individual panels, P to R. The average temperatures of specimens and surroundings are listed in SI Appendix, Table S2.

Fig. 3.

The thermal landscape of (A) C. albicans, (B) C. neoformans H99, (C) C. neoformans cap59, and (D) Penicillium spp. colony. Close-up of a single yeast colony thermograph shows that the coldest temperature of a colony appears at its center and the warmest temperature of the surrounding agar appears near the colony edge.

Fig. 4.

Evaporative cooling in yeast and mold colonies. The evidence for evaporative cooling is observed from the condensed water droplets at the lid of the petri dish on top of the colonies. Visible (Top and Middle) and thermal images (Bottom) of (A) wildtype H99 Cryptococcus neoformans; (Scale bar, 1 cm.); (B) cap59 acapsular mutant of C. neoformans colonies; (Scale bar, 1 cm.), and (C) normal Penicillium spp.; (Scale bar 3 cm.) Visible images (Middle row) were altered to increase contrast and help visualize water droplets (arrows).

Fig. 5.

Proof-of-concept of a mushroom-based air conditioning system constructed from Styrofoam boxes and A. bisporus mushrooms. (A) Model diagram model of MycoCooler™ air conditioning system inside a semiclosed chamber. Warm air enters an insulated chamber containing mushrooms. As the warm air flows inside the chamber, mushroom-mediated evaporative cooling will cool the air. An exhaust fan will push the cooled air through a HEPA filter to limit spore dispersal and enhance air circulation. The fan can be powered via a photovoltaic cell making this system free of carbon emissions. See prototype images in SI Appendix, Fig S6. (B) Air temperature and RH as a function of time inside a Styrofoam box as the semiclosed system. The black arrow points to the time when commercially available and detached mushrooms were added inside MycoCooler™; once the temperature inside the Styrofoam box semiclosed system reached a steady state.