This is one of the stories Kirby did for the DC fantasy/sci-fi books in the late 1950s, the same era he was also doing Green Arrow, Challengers of the Unknown and the Sky Masters comic strip.
In this 8 page story, two scientists discover a destructive microbe in their lab. To destroy it, they try a positive ion beam on it. Unfortunately, the next day they find it has grown to huge proportions, destroying everything in its path and continuing to grow, threatening untold havoc if unchecked.
They notice that the creature doesn't seem to be able to affect glass, leading to some lovely pseudo-science revealing that a negative ion charge will shrink the creature.
A fairly standard story, but some nice art like the image of a hypothetical city-sized microbe on the loose.