Sexual Magnetism as an Infection – How Red Dwarf Got Close to the Truth

The sitcom Red Dwarf has an episode where the crew boarded a derelict ship and discovered the remains of research into positive viruses, like luck, inspiration, and sexual magnetism. Scientists are finding that the writers were correct: some infections can increase your attractiveness.

The Sexual Magnetism Virus

The sexual magnetism virus has already been discovered, and it has a name. It’s called the Cucumber Mosaic Virus, but you don’t have to be a cucumber to catch it. Sadly, you do have to be a plant.
Cucumber Mosaic Virus infects a lot of plants, but when it does it’s bad news. It seriously harms the plant, stunting its growth and damaging its fruits. Yet it’s also difficult to remove. For some reason, it’s really infectious, and now we might know why. The virus changes the smell of a plant’s flowers, making them much more attractive to pollinators.

Dr. John Carr, Head of Cambridge’s Virology and Molecular Plant Pathology group said: “We were surprised that bees liked the smell of the plants infected with the virus – it made no sense. You’d think the pollinators would prefer a healthy plant. However, modelling suggested that if pollinators were biased towards diseased plants in the wild, this could short-circuit natural selection for disease resistance.”

By getting more pollinators to the sick plants, the virus is making the bees select the most suitable hosts for the next generation of virus. The reduced seed set isn’t so much a problem if the plants are getting pollinated much more often. The virus is effectively breeding a variety of plant to produce more suitable victims.

The way the virus works is through ‘volatiles’: these are the chemical scents that plants produce in their flowers. Get the chemistry right, and your flower is irresistible to passing pollinators like bees. However, it’s not just the flowers that give off volatiles. Research just published has looked at microbes living in the flower nectar, and found that attraction could also be the result of a yeast infection.

The Sexual Magnetism Yeast Infection

Yeasts are single-celled fungi and the organisms that convert sugar into alcohol, giving Holsten Pils its distinctive second-hand taste. Nectar is basically a sugary soup, so it’s perfect. Or at least it would be, if it weren’t such a temporary environment. These habitats don’t last long, so as soon as yeast arrives in the nectar, it needs to start working on hitching a lift back out. What Caitlin Rering and her colleagues have found is that it’s not just the flowers that work to attract pollinators. The yeast is signalling too.

The team tested a variety of microbes inhabiting nectar, including Metschnikowia reukaufii, a yeast that specialises in nectar and relies on pollinators to move it from one flower to another. They did this by collecting bees, feeding them to make sure they were healthy and then starving them for two hours, so they could be sure they were ready for a meal. They then provided them with sugar solutions with either nothing special, or various microbes in it – which would be signalling.

On the whole, the bees preferred their sugar solution uninfected, with one exception. Sugar solution containing the Metschnikowia reukaufii yeast was more attractive than the control sample. Whatever scent the yeast was giving off, it was attracting the attention of the bees.

At the moment the research is in the early stages, so Rering’s team are open to the idea that Metschnikowia reukaufii isn’t so much attractive as not giving off something repulsive to bees like other microbes might. Still, it looks like plants can be made more attractive if scientists can work out what a suitable infection for a plant is. That might sound like something only a microbiologist could be interested in, but it could have an impact across agriculture.

Why Do We Need Sexy Plants?

While he has no desire to infect plants with the current Cucumber Mosaic Virus, John Carr is eager to learn the way it works. “Better understanding the natural chemicals that attract bees could provide ways of enhancing pollination, and attracting bees to good sources of pollen and nectar – which they need for survival,” he said.

The payback is that when you attract the bees, you also help target pollination to the plants that matter to you. Enhanced pollination could help improve crop yield and bring down the price of a lot more than cucumbers and tomatoes in your local supermarket.

We tend to think of infections as malevolent. That’s no surprise when they tend to make us feel unwell as they use our bodies for their own means. However, it’s better to think of them as selfish. That means they’re capable of having some positive effects, if it serves their own means. We’ve domesticated animals and plants. Is Red Dwarf right to suggest the next step is to domesticate microbes and infections?

You can find out more about Red Dwarf, including where and how to watch it at the Official Site.