What is a Microbe? Microscopic organisms that exist as single cells or cell clusters. Too small to be seen w/out a microscope.

Classified into 2 Categories Prokaryotes: organisms that do NOT have a membrane-enclosed nucleus. Ex) Bacteria Eukaryotes: contain membrane- enclosed organelles such as a nucleus. Ex) Animal Cells and Protists

Viruses Tiny NON-LIVING particle that enters and then reproduces inside a living cell. Considered to be NON-LIVING because they are not cells and cannot make or take in food.

Size of Viruses

Structure of a Virus All viruses have 2 basic parts: a protein coat that protects the virus and an inner core made of genetic material. Come in different shapes.

Filovirus Do not have a distinct, uniform shape Ex)Ebola

Polyhedral Virus Geometric appearance, look like crystals Ex) Polio

Envelope With Projections Spherical shape with projections Ex) Flu, HIV

Bacteriophage Resembles a spacecraft. Attacks only bacteria Ex) E.coli

How Viruses Multiply Although viruses can multiply, they do so differently than organisms. Viruses can multiply ONLY when they are inside a living cell. Host: organism that provides a source of energy for a virus or another organism. Parasite: an organism that lives on or inside a host and causes it harm.

How Viruses Multiply Once inside a cell, a virus’s genetic material takes over many of the cell’s functions. It instructs the cell to produce the virus’s proteins and genetic material. The proteins and genetic material then assemble into new viruses.

Active v. Hidden Active viruses enter cells and immediately begin to multiply leading to the quick death of the invaded cells. Hidden viruses “hide” for a while inside host cells before becoming active.

Active Virus

Hidden Virus