Mycotoxigenic fungi and how they adapt to climate change? (Interview)

Mycotoxigenic fungi are a pressing concern in the food and animal feed industries. Hence, it is a very appealing and important subject for many specialized research groups around the globe.

Ángel Medina, Full time Professor and researcher is part of the Applied Mycology Group at Cranfield University (United Kingdom). His studies focus on the impact of environmental stress on the functioning of fungi, the mechanisms involved in ecophysiological tolerance and the molecular basis of secondary metabolite production. Especially that of mycotoxins and other relevant metabolites for industrial applications.

You have a PhD in microbiology from the University of Valencia and are currently carrying out your research within the applied mycology research group at Cranfield University. What led you to become interested in this field of research?

I did my PhD in Valencia under the direction of Prof. Misericordia Jiménez. At the time, the presence of ochratoxin A in wine and beer was known but the responsible fungi were not as apparent.

        Therefore, most of my PhD was about the discovery of the fungi that produc mycotoxins in grapes or barley.

However, I found the publications of Prof. Naresh Magan (Cranfield University) to be very interesting. Where he  shows that no matter what a fungus can do, it is a matter  of controlling the environment in which it lives.

After thousands of fungi plates and characterizing fungi using different techniques, the concept of “fungi ecology” became very appealing to me.

I applied for a stay at Cranfield in my final year of PhD and that was it… I knew from the beginning that I wanted to go back. And here I am.

Could yo tell us about the main lines of research or the most interesting ones you are carrying out?

One of the most interesting things about working at Cranfield is that I work directly, or am involved, on many different projects on different topics. We examine the benefits and dangers. From all this, I would say that in the last 5 years my research has focused on:

» Ecophysiology of fungal species, mainly those that produce mycotoxins, and the effects that environmental factors predicted by climate change may have on mycotoxigenic fungi

» High-performance techniques to accelerate ecophysiological studies

» The development of early forms of fungal detection or fungal activity.

You have focused on the ecophysiology of mycotoxigenic fungi. What does this concept mean and what kind of information does it provide to us?

For me, ecophysiology is a primary aspect when it comes to mycotoxigenic fungi.

The first rule when you want to win a “war” is to know your enemy.

This is what understanding the ecophysiology of a fungus resembles.

You get to know in what conditions they will grow or not, if they will produce toxins or not,and whether they will reproduce or not, amongst other aspects.

What are the environmental factors that most influence the development of mycotoxigenic fungi and the production of mycotoxins?

 I may be a bit biased!  But so far, the ones I’ve found have the most effect are water activity and temperature.

Right now, we are conducting a lot of research in relation to rising CO2 levels, as we think it could be very important in terms of Climate Change.

Temperature, pH  and water activity have a major influence on these fungi’s life cycle right? Are these factors independent or can the variation of one of them influence the effects of the others? Could you give an example of such phenomenon with a specific mycotoxigenic fungus? 

Our research at Cranfield is known by other colleagues as we are one of the few groups trying to combine 3 environmental factors simultaneously in some experiments.

In this case, in our experiments with Aspergillus flavus we have combined:

• Temperature
• Water availability
• CO₂ concentration

Our tests revealed that there is an interaction between these parameters and that the changes cannot be explained by individual or a pair of changes alone.

In other cases, such as with some Fusarium spp., we have observed that by adding CO2 in the mixture, there is an extension of the water activity and temperature range in which the fungus can grow.

Thus, the fungus can grow at higher temperatures and in drier conditions.

Climate change is a pressing global concern. How are mycotoxigenic fungi being affected by this phenomenon?

I think that nature in general is being affected by these tremendous changes.

One of the most significant changes, and surely everyone has felt it, is temperature fluctuation.

I remember when I was a kid I would run around on my birthday in November in a very thick jacket. This does not happen anymore in my hometown, Carcaixent (Valencia – Spain). Where even in some years people wear t-shirts until mid-December.

Another thing that has changed a lot is the way in which it rains. Therefore, due to climate change, what is changing the most are those same factors that will affect fungi. Which are the ones I mentioned earlier: temperature and water availability.

Remember that survival is the main impulse of all living organisms, and fungi are no exception to the rule. In order to survive they will move towards “better places with better living conditions.” However,when it comes to humans and as far as our food security is concerned, this represents a great risk.

Therefore, it is better that we prepare ourselves.

Has there been a variation in the occurrence of mycotoxigenic fungi in relation to climate change? Which ones should concern us the most for the future?

Currently available studies suggest that several things will change. However, looking at the different mycotoxigenic fungi, both in Europe and in other areas of the world, I think Aspergillus flavus and aflatoxins are a big concern.

This is due to the fact that this “guy” is a tough “guy”. It can survive in very bad conditions during winter, and is capable of thriving under very restrictive conditions (high temperature and low water availability.) Conditions where other fungi or microorganisms cannot grow, and this means they have no competition.

Considering the increase in temperature and drought problems, decreased rainfall, etc., it can be quickly understood that these environmental fluctuations create ideal conditions for this fungus to prevail over others. Allowing it to spread to different areas where it was not a major concern before or could not even grow.

In itself, this won’t be a problem, but A. flavus comes with the added potential problem of producing mycotoxins under those conditions and I think it’s worth remembering that aflatoxin B1 is the most potent mycotoxin and a clear carcinogen for humans.

Within your scope and lines of research, you have analyzed the gene expression of different strains of mycotoxigenic fungi. Have these studies revealed significant changes? Have any remarkable epigenetic effects been observed related to air composition, environmental pollution or pesticide use? Have you found and concrete examples of these types of changes?

Yes, of course! We always try to find the reasons behind mycotoxin changes, by investigating what happens to genes in the biosynthetic pathways of toxins.

This is what we call “molecular ecology“. It has helped us to have  a better understanding of how fungi adapt to specific environmental conditions and why they change the amount of toxin they produce.

In the research that our group has carried out in the last 15 years we have highlighted that environmental conditions are capable of modifying the expression of these genes and therefore modifying the amount of toxins produced.

We have described for different fungi, that mild stress sometimes enhances the expression of some genes that lead to an increase in the accumulation of mycotoxins.

In fact, most mycotoxigenic fungi have maximum mycotoxin production under conditions that are just slightly different from their optimal growing conditions. This shows that mild stress increases the production of mycotoxins.

As mentioned above, most of these experiments have always considered one or two factors and their potential interactions.

In our most recent studies, as aforementioned, we have been evaluating three factors simultaneously adding _CO2 in our climate change experiments. We have seen clear interactions that in some cases lead to a sudden increase in the production of toxins.

Could we say that mycotoxigenic fungi are adapting to climate change at a faster rate than other plant species of interest for animal feed?

Well, microorganisms generally have greater adaptability than other living organisms because their life cycle is short and therefore they replicate many more times in the same period of time.

However, I do not think we have seen major modifications derived from genetic modifications in a very short period of time, as this will happen more in the long term.

What we are seeing is the movement of species and pathogens to areas where they were not found before.

» Some plants will be exposed to these new pathogens and may not be ready.

» Our agricultural practices might not minimize the development of these pathogens, so we wouldn’t be prepared either.

Storage conditions of raw materials are very important to avoid the production of mycotoxins. Which parameters are essential to be monitored in this regard?

This question is closely related to the research we have been developing at Cranfield for the European project MyToolBox.

At Cranfield we have been working on developing an improved decision support system for those that are responsible for silo storage.

Currently, silos are monitored with temperature and humidity sensors.

However, from our experience and our talks with industry members, once you have an alert it means that the situation is already bad enough and losses can be significant.

Therefore, we decided to look for options to improve detection. After examining different alternatives, we decided to study whether CO2 levels linked to temperature and humidity could be a good indicator of fungal activity.

⇒ At a certain level of temperature and humidity, the grain continues to breathe at a specific rate.

⇒ Silos are semi-closed systems and if there is a disturbance in the system in terms of water, temperature or fungal contamination, the respiration of the grain and that of the fungi which grow, will vary from the normal pattern in specific silos.

⇒ The specific location can also be identified.

WITH THIS WE CAN CREATE AN ALERT SYSTEM

Our results in in vitro experiments  and in small silos with 2 tons of wheat or corn (in collaboration with Michelle Suman de Barilla in Italy) have shown that we can set fungal deterioration alerts before systems based solely on temperature and humidity.

From your experience, are there other mycotoxins that should be included in the analyses being carried out currently, which have not been previously contemplated?

That is the “million dollar” question for many.

At Cranfield we are in close contact with companies and most of the things we do are in collaboration with them.

Therefore, we are aware of the limitations and problems that mycotoxin analyses pose to them.

On the other hand, we focus on consumers, both human and animals. Which we want to keep healthy.

It is a compromise between what we have in food and animal feed, and its effects.

It’s very difficult to answer such question. However, I would like to highlight something about this matter.

Legislation is now based on specific relationships between food/feed and mycotoxins, which is based on current toxicological and occurrence data.

Our research and some trends that we have observed in research papers, indicate that trends in mycotoxigenic fungi and mycotoxins are changing.

For example, we are starting to have problems with aflatoxins in areas and in crops where they were not a problem before.

AND, PREVENTION IS THE BEST STRATEGY!

What advice or final takeaways would you give to our readers in regard to mycotoxin control in feed materials?

I feel the pressure of the final question now!

I think the best advice I can give to everyone who reads me is to keep an open mind.

The way we grow and produce food and feed will be greatly affected in the coming years due to climate change.

In fact, we are already noticing these changes in some areas and regions of the world. Therefore, we need to be prepared for unprecedented mycotoxigenic challenges in areas where there were no problems before.

Don’t think “this is none of my business”, “we’ve never had this problem before”, because it may be close to knocking on your own door and you need to be prepared, so, say “hello!”