Bacteria & Viruses

Essential Understandings for Bacteria & Viruses:

Bacteria are made of cells and are alive. The average bacteria cell is between 1 and 10 µm (microns) long. Some bacteria are bigger. Bacteria have been on earth for billions of years. We know this from the fossil record and the age of rocks.
Most bacteria are harmless to humans, some are helpful to humans, and some cause diseases in humans. Many foods contain helpful bacteria such as yogurt, buttermilk, beer, sourdough bread, kimchi, and chocolate, among other foods. Diseases caused by bacteria include Lyme disease, Tuberculosis, Salmonella, Legionella, and Syphilis.
Before the discovery & production of antibiotics in the mid 20th century, half of all human deaths were caused by bacteria. Alexander Fleming discovered that certain types of fungus produced a substance that could kill bacteria. This substance he called penicillin, and became the first antibiotic. Today, we are able to produce many synthetic forms of antibiotics. Some species of bacteria are evolving & adapting to resist antibiotics.
Viruses are much smaller than bacteria, and they are not alive. Viruses do not grow, or metabolize, and cannot reproduce on their own. Most viruses are less than 1 µm micron and are measured using nanometers. 1 micron is equal to 1000 nanometers (nm).
In the picture above, a type of virus called a phage is attacking one bacterial cell. The virus needs to take over a bacteria cell in order to reproduce. Viruses cannot reproduce on their own, they need other cells to reproduce. Viruses do not grow. New viruses are "assembled" by the cell that they have entered and burst out in millions to infect other cells. Viruses are not cellular, they are made of primarily two bio-molecules; nucleic acids (DNA or RNA) & proteins.