Virus, So Unlike Everything Else

This book I bought for my daughter, The Bacteria Book, said that the an E. coli bacteria cell divides into two every 20 minutes. If there’s enough food:

“After 12 hours, one bacteria cell can grow and divide into 70 billion.”

Whoa! How short is their life if they reproduce like this, I thought.

 

But I’d forgotten nature is red in tooth and claw. The point was brought home in Carl Zimmer’s (very) short book, Rabbits with Horns and Other Astounding Viruses, where he wrote:

“Marine viruses are powerful because they are so infectious. They invade a new microbe host ten trillion times a second, and every day they kill about half of all bacteria in the world’s oceans. Their lethal efficiency keeps their hosts in check.”

Take cholera, a water-borne disease caused by the bacteria named Vibrio:

“Vibrio are host to a number of phages (viruses that kill bacteria). When the population of Vibrio explodes and causes a cholera epidemic, the phages multiply. The virus population rises to rapidly that it kills Vibrio faster than the microbes can reproduce.”

Imagine that!

 

Another fascinating point on viruses was their sheer variety. But first, some context:

“The genes in a human and the genes in a shark are quite similar – so similar that scientists can find a related counterpart in the shark genome to most genes in the human genome.”

On the other hand:

“The generic makeup of marine viruses… matches almost nothing… Only 10 percent of them showed any match to any gene from any microbe, animal, plant, or other organism – even from any other known virus.”

So why so much variety in viruses?

Lots of hosts out there: “Each lineage of virus has to evolve new adaptations to get past its host’s defenses.”

Host cells “sometimes accidentally adds some of its genes to them”! These viruses then go on to find another host:

  1. “By one estimate, viruses transfer a trillion, trillion genes between host genomes in the ocean every year.”
  2. For example: “Scientists have even found free-floating viruses with photosynthesis genes, searching for a new host to infect.”

 The second point above is why Zimmer says:

“Darwin may have envisioned the history of life as a tree. But the history of genes, at least among the ocean’s microbes and their viruses, is more like a bustling trade network, its web reaching back billions of years.”

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