Bacteria and Viruses

Unit 1: Nature of Biology

Prokaryote Characteristics

Prokaryotes have:

Cell Membrane

Cytoplasm

Genetic material

Prokaryotes do NOT have:

Nucleus

Membrane-bound Organelles

Example: Bacteria

Bacteria

Bacteria

Unicellular prokaryotes

Are living

Bacteria are found everywhere and can use just about anything for energy.

Bacteria move using whip-like structures called flagella or oozing a slime layer.

Bacterium with Flagella

Bacteria

Bacteria also come in different shapes

Rod-shaped are called bacilli

Round are called cocci

Spiral

E. coli Bacterium

Roles of Bacteria in the Environment

There are many helpful bacteria, such as the bacteria found in your intestines.

Some Bacteria:

Carry out photosynthesis

Recycle Nutrients

Carry out nitrogen fixation (for plants)

Bacteria

Bacteria reproduce by fission. This means that they split in two.

The growth rate of most bacteria will be slowed at low temperatures. Most bacteria die at high temperatures (above 100oF).

Viruses

A virus is NOT a “true” cell.

It is not considered living.

Viruses exist for one purpose: to reproduce!

They cannot reproduce on their own. Viruses MUST have a host cell copy their DNA for them.

Viruses & Characteristics of LifeMade of Cell(s)

Maintains Homeostasis

Uses Materials & Energy

Grows & Develops

Contains DNA (genetic code) Note: Some only contain RNA

Reproduces Note: MUST have a host

Evolvescopyright cmassengale 11

Viruses

All viruses are made of proteins and nucleic acids.

Viruses have two parts:

Protein coat = capsid

DNA or RNA that contains the instructions for replication

Viral Reproduction A virus will attach itself to a host cell.

It then injects its DNA into the cell.

The cell copies the DNA, which makes more of the virus.

Eventually, the cell will burst releasing all the new viruses.

Viruses cause infections by entering body cells and replicating.

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Attachment:Phage attaches to host cell.

Penetration:Phage pnetrates host cell and injects its DNA.

Merozoites released into bloodsteam from liver may infect new red blood cells

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2

3

Bacterial cell wall

Bacterial chromosome

Capsid DNA

Capsid

Sheath

Tail fiber

Base plate

Pin

Cell wall

Tail

Plasma membrane

Sheath contracted

Tail core

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4 Maturation:Viral components are assembled into virions.

Tail

5 Release:Host cell lyses and new virions are released.

DNA

Capsid

Tail fibers

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Bacterial Infections

Bacterial infections can be treated medically using antibiotics, which will target the living prokaryotic cells.

Antibiotics do NOT work against viruses!

Viral Infections Viruses have to be PREVENTED

or treated with anti-VIRALS.

Viruses can be prevented using a vaccine.

A vaccine contains an inactive or weak version of the virus.

It exposes your immune system to the virus so that the body can build up defenses.

Bacteria vs. Viruses

A living Prokaryote

1000x smaller than eukaryotes

Reproduces itself (through fission)

Treated using antibiotics

Not living

100x smaller than a bacterium

Must have a host copy its DNA

Vaccines used for prevention

https://www.youtube.com/watch?v=zQGOcOUBi6s

http://learn.genetics.utah.edu/content/cells/scale/

https://www.youtube.com/watch?v=s-HThHRV4uo

https://www.youtube.com/watch?v=cE0qdqoBFa8