Class Notes 1: Bacteria and Virus

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

D. What is the structure of bacteria? 1. Their DNA can be found in a single circular chromosome. 2. They have a cell wall, which prevents the cell from bursting.

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

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

IV. 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.

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

C. What is the structure of a virus? 1. A typical virus is made of a DNA or RNA center, surrounded by a protein coat, called a capsid.

D. How viruses work 1. Lytic Infection A virus enters the cell, makes copies of itself, then causes the cell to burst

2. Lysogenic Infection A virus inserts its DNA into the cell. The host cell copies its own DNA, and also that of the virus. . Can go through dormant/active cycles

E. Viruses and illness Viruses cannot be destroyed by antibiotics. 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 What is the difference between bacteria and viruses?