SKIN WARRIORS

The human skin is a veritable ecosystem, teeming with microbes that wriggle around, have turf battles and vanquish enemies

Microbes have been around longer than anything else on this planet. Fossils of these single-celled creatures date back more than 3.5 billion years. They became so good at survival8212;thanks to superfast reproduction and smart mutations8212;that now they are everywhere. If all the microbes on and in the earth could be gathered in one place, they would take up more space than all the animals put together. We don8217;t see them but they are all over us.

Imagine each of us as an active ecosystem. A large part of us that is, the mass of our body is actually something else: microbes of different shape and size. Each of us is host to microbes like bacteria, viruses, fungi and protozoa in our intestines, mouth, eyes, ears, nose and skin. Contrary to popular belief, these are not dirty, dangerous creatures. They produce vitamins, help digest our food and work as an essential part of our immune system.

The skin is the largest organ of our body, and a generous host to microbes. We have between 11,000 forearm to 1.5 million scalp bacteria per sq cm. Many people believe washing will remove these 8220;bugs and germs8221;. In fact, studies show even the most vigorous washing does not remove microbes completely. Babies are born microbe-free, but rapidly pick up their own set of microbial friends and become 8220;saturated8221; within nine days.

A layer of dead cells constitutes the outer section of our skin. Each new cell produced by cell division moves from the inner section of the skin towards the surface. In the process, the liquid component cytoplasm of the cell transforms into a resistant protein known as keratin and the cell dies. This keratin has a very hard structure and cannot be decomposed by digestive enzymes, which is a sign of its resistance. So invaders such as bacteria and fungi don8217;t find anything to rip off from the outer layer of the skin.

Now dead outer cells containing keratin are constantly shed from the skin surface. Feeding on the leftovers stuck on the keratin, a group of harmless microbes live on the skin, which have adapted to its acidic medium. These microbes attack all kinds of foreign bodies to protect their feeding site.

In one experiment, the typhoid bacteria, Salmonella typhi, was smeared on human skin and, within twenty minutes, was completely destroyed by resident bacteria. The same Salmonella tyhpi smeared on a glass slide, after twenty minutes, had remained and reproduced. Though we can8217;t see or feel our tiny 0.1-0.4 mm resident skin microbes, they wriggle around, constantly fighting territorial battles against other, often harmful, microbes.

There are two main types of microbes on our skin: permanent residents and transients. Permanent microbial species live on the surface of the skin and also in deeper layers. Washing off the surface populations simply encourages microbes in the lower layers to come up. However, transient populations, which are picked up from other people or animals, are generally removed by thorough washing.

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Meanwhile, we produce 10 billion skin flakes8212;squames8212;daily. In a year, that amounts to over 2 kg. What happens to these? Well, remember the idea of dust-to-dust? Dust is 90 per cent squames, the favorite food of the peaceful dust mite. Dust mites have evolved to live with us in harmony. A double bed has 2 million dust mites. Studies have found no home free of dust mites. These peaceful squames-munchers are the final link in the skin8217;s ecosystem.

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