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Welcome to Principles of Virology.
I'm Vincent Racaniello and I am a professor at Columbia University in
New York and I've spent my entire career studying viruses.
We live and prosper in a cloud of viruses.
Viruses infect all living things on the planet
and humans regularly eat and breathe billions of virus particles daily.
Furthermore, we also carry viral genomes as part of our own genetic material.
The number of viruses on planet Earth is staggering. Here's an example.
In the world's waters,
there are over 10^30 bacteriophage particles.
A bacteriophage particle weighs about a femtogram.
If you add up all the bacteriophage particles on the planet,
their biomass alone exceeds that of elephants by over a 1000 fold.
This is a particle that you can't even see.
Here's another amazing fact.
If you lined up all of these 10^30 bacteriophages end to end,
they would stretch for a 100 million light years.
That's farther than the nearest galaxy.
Again, the numbers are amazing and these are just bacteriophages.
These are just viruses that infect bacteria.
There are many, many others on the planet as well.
Most of us think of viruses as purveyors of bad news. It's not true.
Most of the viruses on the planet are in fact beneficial.
Let's take the oceans.
There are more viruses in a liter of coastal seawater than there are people on Earth.
Always find that fact amazing.
If you look in the water at biomass shown in these charts, prokaryotes win out.
They have more biomass than protists or viruses.
But if you look simply at particle abundance,
viruses out number protists and prokaryotes in the waters.
Their numbers are huge,
and these numbers have massive effects.
Viruses in the oceans, for example,
are incredibly important for global cycles.
They are important for the degradation of particulate organic matter and its recycling.