Pollen has a microbiome!

27 Feb 2017

Pollen has a microbiome!

The unearthing of pollen’s microbiome has potential for helping us understand the biggest threats to the environment and may change the way we view and treat allergies in the near future.

Research published in SfAM’s Environmental Microbiology journal is the most comprehensive study of pollen microbiology to date.

We spoke to Michael Zasloff, Scientific Director of MedStar-Georgetown Transplant Institute to find out more.

What aspects of this research were exciting for you?

I have forever wondered why we suffer from seasonal allergies. I’ve always thought our body is fighting off pollen because, it doesn’t want a plant to take root! However, there’s a much deeper explanation and it’s because every pollen grain is a vaccine. That is the miracle.

It’s the most perfect nasal vaccine. If you wanted to develop a mucosal response, in other words, you wanted to direct your mucous membranes to deal with an antigen- it could be a virus, but in this case it’s a pollen grain- you would in some way, couple it to a microbe. The body doesn’t care about pollen.

What the body cares about are the bacteria attached to that pollen. When our immune system sees a microbe, it immediately organises the immune system to deal with the assault.

Now I understand why pollen allergy is so common. That’s a big deal.

Will this research will lead to better treatment for allergies?

It could be that we educate the immune system against the bacteria, the microbe associated with the common pollen species- might that have an impact?

What I’m getting at is that there’s a lot of research needed. This is not a cure for allergy. You can’t use this right now and say, ‘here’s a shot of this, that’s the end of your allergy’.

Right now, there are virtually no methods to supress allergy effectively, once it’s developed. We DO have better methods to prevent the onset of allergy, for example- the whole peanut allergy story is now being approached from another direction. Expose the child from a very young age- to peanuts.

My training position, as a paediatrician, was to keep kids away from certain foods. The idea was to keep them from peanuts and eggs, tomatoes and bunch of other things. But turns out- it’s making it worse.

Allergies, whether it’s eczema, hayfever or asthma have a very strong genetic relationship. I would imagine that exposure for children in certain families to the microbiome of pollen, in the world of that child, might be a way to approach this.

I wouldn’t have been able to approach this problem in an experimental way, if I didn’t have the data that came out of that paper. Now, at least there’s a starting block.

How much of the allergies we have to our pets isn’t the same thing? The dander on a cat? I mean, come on! If you looked at the dander particle, you know what that dander’s gonna look like, it’s gonna have colonies of microbes on it. It’s changed the way we’re thinking about inhaled allergies.

And how might this research help our dwindling bees?

Every insect is hardwired. It makes a collection of antimicrobial peptides that defend it from a very specific spectrum of microbes. It will generate an orchestrated response to microbes.

The bee may produce a dozen antimicrobial peptides in a particular concentration. Its response has co-evolved with the organisms it will meet in its search for food. These insects- and most animals, (other than mammals), have very specific niches. Except for vertebrates, most animals have a particular food source- and they stick to it.  They have a very limited range of nutrients. The ultimate expression of that is Darwin’s whole discussion of the co-evolution of the orchid and the specific pollinator.

What’s the deal with orchids?

Every orchid species has a specific pollinator and I’ve never understood that. Nor has anyone explained it. It could be that part of the constraint, is the microbiome of the organism and the immune capacity of the pollinator.

Maybe every orchid species has its own particular microbiome and that’s part of nature’s restriction. It opens up the possibility that if you alter the microbiome of the pollen that is carried by the bee into a hive- do you put that bee colony into a dangerous place? Microbes can grow pretty fast in the warm nest. It’s an incubator. It’s maintained at a constant temperature by the bee. What happens? We don’t have any idea.

After we treat a population of tulips with fertilizer, do we change the microbiome?  There would be no reason to look at that if you didn’t know there was a live population of bacteria growing on the pollen. It would make no sense to ask such a question.

You know why I think this research is important? It gives scientists work. Once something gives a scientist work- it’s usually an important discovery.

Why hasn’t the microbiome of pollen been studied in this way before?

We are at the beginning of microbiome studies. Everyone is looking at the microbiome of this, that and the other. Also, the cost has dropped for these previously expensive studies.

What other discoveries could stem from this?

There was a paper that argues that there seems to be some impact on pollen’s bacterial composition as a consequence of pollution. Then you suddenly realise that the pollen is also a vehicle for the spread of a particular species of bacteria. That to me is remarkable.

You have a whole epidemiology, in a way. If something is happening in your field and you’ve eliminated or created a whole new grouping of pollen, you are now going to transfer that ecosystem to another one. You don’t think of pollen in flowers to be carrying bacteria. Now you do!

Think of the corn plant and all of these crops we grow. It’s the same thing-those that require fertilisation. Trees? Just an enormity. Every flowering plant has this population and has a particular affinity for certain organisms. What does perturbation lead to? I dunno. It’s like a new field. That’s why it’s so exciting.

One of the most amazing things is that it takes an enormous amount of energy for plants spend to create and manage genes that play a role in defending various parts of the plant against microbes- because that’s all they have. You take a tree, a redwood tree or ANY tree that’s been living for thousands of years. It can’t move. It has to stay where it is. The antimicrobial defences that it requires are basically the same type that the bee is using. And very similar to what we use.

We’ve lost a lot of olive groves to bacterial diseases in Europe..

These olives are flowering plants or they wouldn’t make olives. When the pollen lands on the female portion of the plant and begins to make its way down, the progress is orchestrated by antimicrobial peptides that are also monitoring organisms entering the embryo.

God knows what happens if the wrong microbes are on that pollen. Do you alter the outcome of that fruit? What happens to the overall life cycle of that plant? Maybe you can’t kill a microbe that enters the embryo. Maybe that seed becomes weak. It’s so complicated. These are is not well studied. It’s not often that you get a paper with this much behind it- it’s amazing.

Michael A. Zasloff is an American doctor, immunologist, medical researcher, professor, and geneticist. He is currently Scientific Director, MedStar-Georgetown Transplant Institute, Georgetown University Hospital.

This interview is in response to a research article published in Environmental Microbiology titled ‘Bacterial microbiota associated with flower pollen is influenced by pollination type, and shows a high degree of diversity and species-specificity‘.