Disease-causing agents are called pathogens. It is the broadest term that can be used which refers to any bacterium, viruses or any microorganism that causes disease. It is also known as infectious agent. It can also be defined as an agent that disrupts the normal function of a multicellular animal or plant.
Double helix like a spiral ladder
Both plant and animal development is seeded in the perspective that a cell divides itself to form a tissue and tissues grouped will become an organ and the organism itself. The cell hierarchial model is followed in the development in both of these diverse however seemingly similar organisms.
I think it might be lyosomes as they help break down waste and other stuff in a cell.