They have internal skeletons which cover their skin. The body of an echinoderm seems little more than a skeleton of tiny plates and water. They don't use large muscles working on large body parts like many other animals. Instead they move, feed and breathe with a unique water-vascular system ending in hundreds of water-filled tube feet.
Knowing whether a bacteria is gram positive or negative will help to narrow down the types of pathogen it could be and will determine which antibiotics will be effective against it.
