@earlyforest -- I assume you want to know more about the physical characteristics of a gram negative bacillus? Bacteria species vary so much that there's not really one behavioral characteristic of gram negative bacteria, so I'll stick with the physical.
The main difference between gram negative or positive bacteria is the structure of their cell wall. Gram negative bacteria have more layers to their cell walls than gram positive bacteria, which can protect the bacillus from some antibiotics, detergents, or dyes, and can also act an an endotoxin, which is what causes the body to get sick.
Although this is a very basic overview, that is the main difference between gram positive and gram negative bacteria, in layman's terms -- hope that helps you!