Bacteria are much larger than viruses. They range in size from 1 micron to 200 microns. A good place to see the difference in sizes can be found at Cells alive. There you can see that bacteria are about 10 times bigger than viruses. Bacteria are still quite small and require the aid of a microscope to see the individual organisms.
However, when grown on a nutrient containing medium the organisms grow into large "cities" of growth called colonies. There can be up to one billion cells in a colony. If you follow this link you can see plates containing colonies of cells. The small round dots are called colonies.
Bacteria also come in a variety of shapes and sizes. Bacteria are round(cocci), rod-shaped, and spiral. Bacteria are found everywhere. Even in the deep sea vents. They are important in the making of antibiotics, breakdown of our compost piles, and for making sauerkraut! They can also cause diseases.
Now, Why did I say that bacteria are gutless? This statement could get me in trouble with the SPCB (The society for the protection from cruelty to bacteria). The reason I said bacteria are gutless is because they are. They lack certain specialized structures called organelles. The cells that make up you and I contain organelles. Organelles are like the organs in our bodies. Each has a specialized function (eg. Our heart pumps blood.). The organelles in our cells also have specialized functions (eg. The cell nucleus protects our DNA.). In addition to the cell nucleus we have the golgi complex, endoplasmic reticulum, and mitochondrian, in our cells.
Bacteria live and grow just fine without these organelles. An excellent site that compares prokaryotes (gutless critters) with eukaryotes (our cells) is Dr. Hurlbert's site. Here is another great site that tells you more about our organelles as well as another organelle that is special to plants. For information about bacteria go to What is Microbiology or to Dr. Baron's Medical Microbiology book
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