Class Notes 3: Domain Bacteria, Domain Archae & Viruses

I. Domain Bacteria A. Remember that bacteria are prokaryotes. B. This means that they are simple cells. C. They do not have a nucleus or organelles!

II. What is the structure of bacteria? A. Their DNA can be found in a single circular chromosome. B. They have a cell wall, which prevents the cell from bursting.

III. How do bacteria reproduce? A. There are two ways bacteria reproduce. B. Asexually through binary fission and sexually through conjugation.

IV. Bad Bacteria A. Bacteria are responsible for such diseases as strep throat, tuberculosis, lyme disease, cavities, and cholera. B. Fortunately, we have antibiotics to fight off bacterial infections.

V. Good Bacteria A. Nitrogen fixing bacteria live in the roots of peas and other legumes, adding nitrogen to the soil.

B. Bacteria recycle dead organisms back into the earth. C. Vinegar, yogurt and cheese are all made with bacteria. Yum!! D. Good bacteria live in your digestive system.

VI. Domain Archae A. Archae are also prokaryotes, and they have a similar function and appearance to bacteria. B. Molecular evidence shows Archae are not closely related to bacteria. C. Bacteria have a polymer called peptidoglycan in their cell walls, Archae do not.

VI. What is a virus? A. A virus is considered non-living, so it is not in a domain. B. It invades host cells and uses the machinery of the invaded cell to make more viruses. Influenza-->

VII. What is the structure of a virus? A. A typical virus is made of a DNA or RNA center, surrounded by a protein coat, called a capsid.

VIII. How viruses work? A. Lytic Infection A virus enters the cell, makes copies of itself, then causes the cell to burst

B. Lysogenic Infection A virus inserts its DNA into the cell. The host cell copies its own DNA, and also that of the virus.

C. Viruses and illness 1. Viruses cannot be destroyed by antibiotics. 2. A vaccine is a weakened version of a virus that allows your body to build immunity to the virus, hopefully preventing you from becoming ill.

Summary Why are Bacteria and Archae in separate domains? What is the difference between bacteria and viruses?