Resistance to plant toxins in milkweed butterflies is linked to toxin storage for defense

A monarch caterpillar feeding on milkweed (Credit: OakleyOriginals. CC BY 2.0)
A monarch caterpillar feeding on milkweed (Credit: OakleyOriginals. CC BY 2.0)

When your only food source also contains a deadly poison, your options are pretty limited: either find a new food source or find some way of making the poison less toxic. This is exactly the situation that many plant-eating insects find themselves in, particularly those that eat milkweed.

Milkweeds produce a class of chemical toxins named cardenolides. These compounds specifically bind and inhibit the sodium potassium pumps found in heart muscle cells. Without working pumps sodium levels in the cell rise, setting off a chain of events that ultimately disrupt muscle contraction in cardiac tissue. At a high enough dose, these heart-stimulating effects can be lethal to insects, humans and animals in between. How then do insects that depend on milkweed as their main food source cope with this hidden poison? Continue reading

Less toxic staph cause more severe disease

A scanning electron micrograph of methicillin-resistant Staphylococcus aureus and dead human immune cells. (Credit: National Institute of Allergy and Infectious Diseases. CC BY 2.0)
A scanning electron micrograph of methicillin-resistant Staphylococcus aureus and dead human immune cells. (Credit: National Institute of Allergy and Infectious Diseases. CC BY 2.0)

We hear a lot about toxins in the news these days. Specifically, the hidden toxins lurking in the food we eat, the household products we use, the air we breathe and why we need to go on a juice cleanse to detox our bodies, lose weight and feel great!

But right now, let’s ignore those exaggerations and pseudoscience (because that’s a lengthy post in and of itself) and talk about real toxins. Real bacterial toxins. These toxins are proteins made and secreted by bacteria that help them establish an infection and cause disease. Staphylococcus aureus, commonly known as staph, is one species of bacteria that deploys a large and diverse arsenal of toxins. Most people carry staph bacteria asymptomatically on their skin and in their noses. In certain individuals, such as those with a weakened immune system, the bacteria can cause a wide spectrum of diseases from minor skin and soft tissue infections to life-threatening pneumonia and bloodstream infections. A key component of the bacteria’s survival strategy are the toxins that damage tissues and attack immune cells to interfere with the host’s defense system. Toxins are also responsible for disease symptoms such as the skin lesions commonly seen in patients with a staph infection.

Given the important role that toxins play in establishing and maintaining an infection, it would be logical to assume that the more toxins a bacteria produces, the more severe the infection. Until recently, that was the prevailing belief in the research community. Continue reading