"The biology song 07" joke

Away in a Test Tube
(Melody: "Away in a Manger")

Away in a test tube
My plague cultures grow
On nutrient agar
Mankind's greatest foe

It's easy to grow them
If one does it right
At thirty-five Celsius
All day and all night

Once they are ready
You can let them go
To sicken the masses
With pus-filled buboes.