Smith Daniel F Q, Bencomo Alexa, Faiez Tasnim Syakirah, Casadevall Arturo
W. Harry Feinstone Department of Molecular Microbiology and Immunology, The Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, 21205, USA.
Krieger School of Arts & Science, Johns Hopkins University, Baltimore, MD 21218, USA.
bioRxiv. 2023 Nov 10:2023.11.10.566554. doi: 10.1101/2023.11.10.566554.
One of the major barriers of fungal infections of mammals is the inability to grow and/or survive at mammalian body temperature, typically around 37°C. This has provided mammals an advantage over fungi. However, environmental fungi may soon adapt to persist at higher temperatures, consistent with mammalian body temperature, due to thermal selection pressures imposed by climate change, global warming, and increased frequency of extreme heat events. Consequently, there is a need for more updated information about the thermal tolerance range of fungi near humans, such as in urban areas. The heat island effect suggests that cities are up to 8°C warmer than their suburban counterparts because of increased heat production, asphalt coatings and reduced greenspace among other factors, and it is more common in lower income and marginalized urban communities. Thus, urban centers are at increased risk for the emergence of heat tolerant fungi. In this study, we developed a methodology to collect and archive fungal isolates from sidewalk and soil samples in both warmer and cooler neighborhoods in Baltimore, Maryland. We demonstrate a novel methodology for fungal sample collection from sidewalks, employing the use of standardized and commercially available taffy. Analysis of fungal isolates collected from warmer neighborhoods revealed greater thermal tolerance and lower pigmentation, suggesting local adaptation to heat. Lower pigmentation in hotter areas is consistent with the notion that fungi use pigmentation to help regulate their temperature. Further, we identified the robust presence of the polyextremotolerant fungus from the warmest neighborhood in Baltimore further showing that the extreme conditions of cities can drive proliferation of extremotolerant fungi. This study develops new techniques for environmental fungal collection and provides insight on the fungal census in an urban setting that can inform future work to study how urban environments may drive stress/thermotolerance in fungi, which could alter fungal interactions with humans and impact human health.
哺乳动物真菌感染的主要障碍之一是无法在哺乳动物体温（通常约为37°C）下生长和/或存活。这使哺乳动物相对于真菌具有优势。然而，由于气候变化、全球变暖和极端高温事件频率增加所施加的热选择压力，环境真菌可能很快适应在与哺乳动物体温一致的更高温度下生存。因此，需要更多关于人类附近（如城市地区）真菌耐热范围的最新信息。热岛效应表明，由于热量产生增加、沥青涂层和绿地减少等因素，城市比其郊区温度高8°C，这在低收入和边缘化城市社区更为常见。因此，城市中心出现耐热真菌的风险增加。在本研究中，我们开发了一种方法，用于从马里兰州巴尔的摩市较温暖和较凉爽社区的人行道和土壤样本中收集和存档真菌分离株。我们展示了一种从人行道收集真菌样本的新方法，即使用标准化的市售太妃糖。对从较温暖社区收集的真菌分离株的分析显示，其耐热性更高且色素沉着更低，表明其对热的局部适应性。较热地区色素沉着较低与真菌利用色素沉着来帮助调节体温的观点一致。此外，我们在巴尔的摩最温暖的社区中发现了多极端耐受真菌的大量存在，进一步表明城市的极端条件可推动极端耐受真菌的增殖。本研究开发了环境真菌收集的新技术，并提供了城市环境中真菌普查的见解，可为未来研究城市环境如何驱动真菌的应激/耐热性提供参考，这可能会改变真菌与人类的相互作用并影响人类健康。
