 [ Symptoms ] what are the differences between bacteria and viruses [ Disease ] although bacteria and viruses are both too small to be seen without a microscope they are structurally as different as giraffes and goldfish bacteria are relatively complex single celled creatures with a rigid wall and a thin rubbery membrane surrounding the fluid or cytoplasm inside the cell shaped like balls rods or spirals they contain all of the genetic information needed to make copies of themselves fossilized records show that bacteria have existed for about 3 5 billion years and it is known that bacteria can survive in a variety of environments including extreme heat and cold radioactive waste and the human body most bacteria are harmless and some    such as the lactobacilli acidophilus bacteria that can live in the human intestine    actually help digest food destroy disease causing microbes fight cancer cells and provide essential nutrients fewer than 1 of bacteria cause disease in people in contrast viruses are tiny the largest of them are smaller than the smallest bacteria viruses come in varied shapes and have a limited genetic blueprint all they have is a protein coat and a core of genetic material either rna or dna unlike bacteria viruses can not survive without a host they can only reproduce by attaching themselves to cells and hijacking the cells cellular machinery in most cases they reprogram the cells to make new viruses until the cells burst and die in other cases they turn normal cells into malignant or cancerous cells also unlike bacteria most viruses do cause disease and they are quite specific about the cells they attack for example certain viruses are programmed to attacks cells in the liver respiratory system or blood in some cases viruses called bacteriophages target bacteria