Viruset och cellen

Här kommer ett utdrag ur boken I Contain Multitudes av Ed Yong. 

Vad man behöver veta innan man läser detta är att många bakterier faktiskt kan vara nyttiga för människor och djur, och finns i miljontals i exempelvis tarmarna.

 

"When you think of viruses, you probably think of Ebola, HIV, influenza: well-known villains that make us sick. But most viruses infect and kill microbes instead. These are called bacteriophages – literally 'eaters of bacteria' – or phages, for short."

"When they touch down on a bacterium, they inject their DNA and turn the microbe into a factory for making more phages. These eventually burst  out of their hosts in fatal fashion. Phages don't infect animals, and they far outnumber the viruses that do. The trillions of microbes in your gut can support quadrillions of phages."

"Rohwer [en forskare] suspects that animals, by changing the chemical composition of their mucus, could potentially recruit specific phages, which kill some bacteria while providing safe passage to others. Perhaps this is one way in which we select for our favoured microbial partners."

"This concept has profound implications. It suggests that phages – which, remember, are viruses – have a mutually benificial relationship with animals, including us. They keep our microbes in check and we, in return, help them to reproduce by offering them a world full of bacterial hosts. Phages are 15 times more likely to find a victim if they stick to mucus. And since mucus is universal in animals, and phages are universal in mucus, this partnership probably started at the dawn of the animal kingdom. In fact, Rohwer suspects that phages were the original immune system – the means through which the simplest animals controlled the microbes at their door. These viruses were already plentiful in the environment. It was a simple matter of concentrating them by giving them a layer of mucus in which to anchor themselves. From this basic beginning, more complex means of control emerged."

Boken I Contain Multitudes av Ed Yong, sida 90-91