The Taste of Light

In nature there are supposed to be only five tastes that make up the human palette. There is sweet, salty, bitter, sour, and savory. Everything else about our taste experience is supposed to come from the texture, aroma, and aesthetics. Yet there are tastes that we identify outside of those areas. For example, there is a carbon taste, a burned food or a metallic “taste.” A recent study from MIT has found a unique mechanism of photosensitivity in the roundworm. These simple organisms have been shown to detect light by tasting it. So just what does light taste like? Bleach.

Roundworms taste light indirectly as they detect hydrogen peroxide and other reactive substances that often result when fragile molecules are damaged by light. This has implications not just for vision, but for our understanding of taste, overall.

Human beings have strong and primitive reactions to the tastes and smell of spoiled food, but for the worm its ability to taste active molecules seems to be serving double duty. Not only does hydrogen peroxide signal environmental hazards, but the molecule-blasting effects of ultraviolet light. Sunlight isn’t strong enough to harm the worm, but the peroxide signal lets the worm know when it’s at or near the surface of soil.

Roundworms are parasites that can infect human beings. They usually reside the intestines. There are different kinds of worms that can cause infection. They range in length from 1 millimeter to 1 meter. Their eggs or larvae live in soil and enter the body when they attach to your hands and you touch your mouth. Some enter the body through the skin.

Like other parasitic diseases, roundworm infections usually happen in warm, tropical climates. Ascariasis is the most common roundworm infection. It affects as many as 1 billion people worldwide.

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