Fungi are everywhere, playing a vital role in ecosystems. However, their activity is highly sensitive to environmental factors, and temperature is one of the most important of these. The effect of temperature on fungal growth influences fungal reproduction, survival, and how fungi interact with other organisms.
Understanding how temperature impacts fungi is critical in many fields, from agriculture to medicine to ecology.
Climate change is changing temperature patterns worldwide, which means that fungal distribution, activity, and even their ability to cause disease are also changing. As the IPCC (2022) reports, Earth’s climate is warming even faster than many climate models initially predicted. This means that the distribution of suitable habitats is also changing for many species, including pathogenic microbes.
This article will explore the many effects of temperature on fungal growth, drawing on the latest research to highlight how these effects are playing out in our changing world. We’ll examine how temperature influences:
- fungal growth rate
- mycotoxin production
- interactions with host organisms
Finally, we’ll explore the thermal mismatch hypothesis as a way to understand plant-pathogen interactions as temperature conditions change.
How temperature impacts fungal growth and metabolism
Temperature is a huge deal for fungi! It affects everything from how quickly they grow to how they reproduce and get food. Think of it like this: Goldilocks and the Three Bears. Fungi have temperatures that are “too cold,” “too hot,” and “just right.”
Cardinal Temperatures and Growth Rate
Like all living things, fungi have what scientists call “cardinal temperatures”: the minimum, optimum, and maximum temperatures where they can survive.
- Minimum: The lowest temperature where the fungus can grow (very slowly).
- Optimum: The temperature where the fungus grows the fastest.
- Maximum: The highest temperature where the fungus can still grow (before it dies).
Fungal species vary widely in their cardinal temperatures, because they’ve adapted to live in different environments.
Temperature directly affects the enzymes and metabolic processes fungi need to grow. Enzymes are like tiny workers that speed up chemical reactions. Higher temperatures can make enzymes work faster, up to a certain point. If it gets too hot, the enzymes break down (denature), stopping growth.
Low temperatures slow down metabolic processes, making fungi grow slower or even become dormant.
How it affects Spore Germination and Reproduction
Temperature is also key for spore germination, which is like a fungal seed sprouting. Spores often need a specific temperature “signal” to start growing.
Also, temperature can influence whether a fungus reproduces sexually (mixing genes) or asexually (cloning itself).
- Some fungi prefer sexual reproduction when temperatures are just right, to create more genetic diversity.
- Asexual reproduction might be favored when temperatures are stable and optimal, because it allows for quick population growth.
For example, high temperatures (above 86°F) have been shown to reduce the ability of anther-smut spores to germinate.
How it affects Nutrient Uptake and Utilization
Temperature affects how well fungal cells can absorb nutrients.
- Higher temperatures can make cell membranes more fluid, making it easier for nutrients to pass through.
- Low temperatures can make membranes less fluid, limiting nutrient uptake.
Temperature can also determine what kinds of nutrients a fungus can use. Some fungi might be able to break down complex carbon sources more easily at certain temperatures.
Temperature can also influence how well fungi produce and use special enzymes that break down nutrients in their environment, a process that can be influenced by pH levels.
How temperature affects mycotoxin production
Mycotoxins are toxic substances that some fungi make. They can be dangerous for both humans and animals, so it’s important to understand the factors that affect when fungi create them. Temperature is one of the most important of these factors.
Specific temperatures can trigger or increase how much of a particular mycotoxin a fungus makes.
But the relationship between temperature and mycotoxin production can be complicated, and it changes based on the type of fungus and the specific mycotoxin it makes. Some fungi create more mycotoxins at higher temperatures, while others make more at lower temperatures. It also depends on other environmental factors, such as water and carbon dioxide levels.
Fusarium and Aspergillus: Case studies
Fusarium fungi are known for creating mycotoxins like trichothecenes and fumonisins. The best temperature for these fungi to make mycotoxins varies with the species of Fusarium and the specific mycotoxin.
One study looked at how climate change conditions (temperature, water, and carbon dioxide) affected how well Fusarium verticillioides and F. graminearum grew and how many mycotoxins they produced.
Aspergillus fungi are known for making aflatoxins and ochratoxins, both of which are potent carcinogens. Aflatoxin production tends to happen more often in high temperatures and drought conditions. The best temperature for ochratoxin production changes depending on the type of Aspergillus.
What it means for food safety
It’s essential to understand how temperature affects mycotoxin production if we want to keep our food safe. By monitoring temperature during food storage and processing, we can reduce the risk of mycotoxin contamination.
The research mentioned above can help us come up with strategies to reduce mycotoxin contamination of crops as the climate changes.
Climate change is expected to change temperature patterns, which could increase the risk of mycotoxin contamination in some areas. Warmer temperatures and more frequent droughts may create better conditions for certain fungi to grow and produce mycotoxins.
How temperature interacts with other environmental factors
Temperature is a big deal when it comes to fungal growth, but it doesn’t work alone. Other environmental factors also play a key role, and they can either amplify or counteract the effects of temperature.
Temperature and water activity
Think of “water activity” as how much water is available for fungi to use. It’s not just about how wet something is, but about how easily the fungi can access that moisture.
Temperature and water activity have a complex relationship. Fungi need a certain amount of water activity to grow, and that amount can change depending on the temperature. For example, when it’s hotter, fungi might need more water activity to make up for the fact that water evaporates more quickly.
Scientists have gathered data that shows specific ways temperature and water activity interact, influencing fungal growth and mycotoxin production.
Temperature and carbon dioxide (CO2)
Climate change is causing CO2 levels to rise, and this can also affect fungi. The relationship between temperature and CO2 is complicated and varies from one type of fungus to another. However, some fungi grow faster or produce more mycotoxins when CO2 levels are high, especially when the temperature is just right for them.
One study found that changes in temperature, water activity, and CO2 had a significant effect on how fast fungi grew and how many mycotoxins they produced.
It’s possible that higher CO2 levels change the balance of carbon and nitrogen in fungal tissues, which then affects their metabolic processes.
Temperature and host interactions
When it comes to fungi that infect plants, temperature can affect how easily the plant gets infected. The “thermal mismatch hypothesis” suggests that pathogens might be more sensitive to temperature changes than their hosts.
For example, one study found that a plant called Silene latifolia was more tolerant of high temperatures than the fungus that infects it.
Temperature can also affect how well a plant defends itself against fungal infections, but vitamins can also boost your immunity. Higher temperatures might help the plant produce defense compounds or activate its immune responses.
Examples of temperature effects on specific fungal-host systems
Fungi and other organisms interact in specific ecosystems. The ways these interactions play out depends on the temperature of the environment.
Microbotryum lychnidis-dioicae and Silene latifolia: A model system
Scientists often use the relationship between Microbotryum lychnidis-dioicae (anther smut fungus) and Silene latifolia (white campion) to study temperature’s effects on plants and the pathogens that infect them.
When temperatures rise above 86°F (30°C), the growth, infection, and transmission of the Microbotryum lychnidis-dioicae fungus slows down significantly.
Warmer temperatures can even lead to the fungus’s demise, creating safe zones where the host plant can thrive.
Studies have shown that high temperatures can “cure” infected plants and that the “heat-curing effect” can occur both in controlled laboratory settings and out in the world.
Different characteristics of the pathogen, such as germination, growth, and conjugation, react differently to heat.
White Pine Blister Rust (Cronartium ribicola)
White pine blister rust is a disease that devastates white pines and is caused by the Cronartium ribicola fungus.
As temperatures warm, the fungus is shifting its range to cooler, higher elevations. This change threatens white pine populations, especially in areas where those populations already suffer from other stressors.
Amphibian Chytridiomycosis (Batrachochytrium dendrobatidis)
Batrachochytrium dendrobatidis (Bd) is a fungus that causes chytridiomycosis, a disease that can kill amphibians.
Bd is very sensitive to high temperatures. As climate change progresses, it may create safe havens for some amphibian populations by limiting the growth and spread of Bd.
Frequently Asked Questions
How does temperature affect fungal growth?
Temperature plays a crucial role in fungal growth. Most fungi have an optimal temperature range where they thrive. Generally, growth rates increase as temperature rises within that range. However, exceeding the maximum tolerable temperature can inhibit growth or even kill the fungus.
Do fungal infections get worse with heat?
Yes, in some cases, heat can exacerbate fungal infections. Warm and moist environments, like those found in sweaty shoes or skin folds during hot weather, can create ideal conditions for fungal proliferation, potentially worsening infections like athlete’s foot or yeast infections.
What temperature destroys fungus?
The temperature required to destroy fungus varies depending on the species. Some fungi are relatively heat-resistant, while others are more sensitive. Generally, temperatures above 140°F (60°C) for a sustained period can kill many types of fungi. However, some resistant spores may survive even higher temperatures, requiring sterilization techniques for complete elimination.
Why do fungi grow faster in warmer temperatures?
Warmer temperatures generally accelerate the metabolic processes within fungal cells. Enzymes, which catalyze biochemical reactions necessary for growth and reproduction, function more efficiently at optimal temperatures. This increased metabolic activity leads to faster nutrient uptake, cell division, and overall growth.
In Conclusion
Temperature plays a huge role in how fungi grow, how they metabolize, how they produce mycotoxins, and how they interact with other living things. Understanding how temperature affects fungi is key to tackling problems in agriculture, food safety, and managing our ecosystems. To predict how warming temperatures will affect the spread of diseases, we need to know how much heat both the host and the pathogen can tolerate.
Climate change is changing temperatures all over the world, which is shifting where fungi live, how active they are, and how likely they are to cause disease. The changing climate is also rapidly changing the distribution of habitats suitable for many species and their pathogenic microbes. As temperatures rise, we’re likely to see an increase in the spread of many important pathogens and their geographic range.
We still need more research to fully understand the complex ways temperature and other environmental factors work together to shape how fungi live and evolve. Future studies need to focus on how multiple climate change factors combine to affect fungal growth and mycotoxin production, instead of looking at isolated factors. Ongoing monitoring and modeling are crucial for predicting how climate change will impact fungal communities and the ecosystems they live in.