When walking by the ocean at the low tide, I look for… nudibranchs - these colorful slugs from the tidepools. Nudibranchs are known to harbor different chemicals, which can be toxic or disgusting to their predators, but if find the right one and we find the right dose, these toxins could be used for killing plant pathogens or cancer cells… 

For our lab experiments, we would need a lot of toxin. But it would be so sad to kill so many nudibranchs, right? Well, with new technologies, that’s not a problem anymore! Through DNA sequencing and genome engineering, it’s possible to read the DNA sequence of the toxin genes and use it as a recipe for producing it in our lab. But! There is still a big question: How do we find the right toxin sequence? 

Researchers in the past just put the toxins in a blender and they automatically assumed, it’s produced directly by the nudibranchs in their skin cells. But, I’m a microbiologist. Knowing that the skin of all humans and animals is full of beneficial microbes, I asked a question: Are there any microbes in the nudibranch skin, helping to produce the toxins? When I started, nothing was known about the bacteria of nudibranch. My research task was to find among the millions of unknown microbes in nudibranch skin the right one! 

For that purpose, our group has developed a special fluorescent molecule, which is absorbed only by bacteria which produce some kind of toxin. We then use a high throughput cell sorter to scan thousands of bacterial cells per second and collect only those ones which have absorbed our special fluorescent molecule… Like a treasure-seeking metal detector on a beach, we discovered… a brand new bacterial species! It forms less than 1% of the total nudibranch skin microbiome, and it would not be detectable otherwise. And what’s more exciting, these bacteria contain genes for production of a previously unknown toxin. 

Our work has revealed an amazing relationship between the nudibranch and the few microbes in its skin cells that are helping to protect it against predators. Imagine if we could demonstrate that this toxin could kill plant pathogens or cancer cells… That would be awesome! Now, always when I’m walking by the ocean, I’m thinking about the bacteria in nudibranch skin, because they are the real treasure from the tidepools.