Chapter 19

Bacteria and Viruses

1. Which of the following characteristics is NOT true of both Archaebacteria and Eubacteria?

A.UnicellularB.All heterotrophicC.ProkaryoticD.Have cell walls

2. Which bacterial kingdom lives in extreme habitats?

A.ArchaebacteriaB.Eubacteria

3. What do you think the root “eu-” means?

A.NucleusB.NewC.TrueD.Green

Bacteria are the simplest and oldest life forms

–fossils show bacteria that are 3.5 billion years old!• The oldest fossil evidence on earth is that of

Archaebacteria.• Archaebacteria are believed to be the ancestors of

both Eubacteria and the other eukaryotic kingdoms

Page 472 DNA

Cell wall

General Bacteria Structure

Bacterial Shapes

• Coccus – spherically shaped • Ex: Streptococcus

• Bacillus – rod shaped • Ex: Clostridium botulinum

• Spirillum – spiral shaped • Ex: Spirillum

Arrangements of shapes

• single cells or in groups• Diplo – two • Ex: Diplococcus (two spheres)

• Strepto – in chains• Ex: Streptococcus (spheres in a chain)

• Staphylo – in clumps• Ex: Staphylococcus (a clump of spheres)

Name these bacterial cells:

4. What would be the name of this bacterial cell?

A.DiplobacillusB.StreptococcusC.StaphylococcusD.Streptobacillus

Draw the following bacterial cells:

• Diplospirillum

• Streptobacillus

• Staphylococcus

Bacteria and You

• Foods made with bacteria: yogurt, cheese, sour cream

• Decomposition• Bacteria are prevalent in sewage treatment plants,

can be used to clean up oil spills, etc.

Bacteria and You (cont)• Bacteria can be pathogenic (disease causing)• Can damage tissues (ex-Mycobacterium

tuberculosis) or can release toxins (ex: Dental cavities and Streptococcus)

• Antibiotics - compounds that block the growth and reproduction of bacteria• Penicillin – fungus that was the 1st antibiotic

5. Which bacterial kingdom do you think is “disease-causing”?

A. ArchaebacteriaB. Eubacteria

Viruses

• poison in Latin• nonliving• don’t fulfill all criteria for life• must infect host cell to reproduce• lack enzymes for metabolism• don’t grow

Virus Shape and Structure• Nucleic acid core • Capsid (protein coat) – gives the virus its

shape

How does a virus infect cells?

1. The virus recognizes a host cell at a specific receptor site.

2. The virus and host cell interlock like a puzzle; a lock and key

3. The virus then destroys the cell’s DNA and takes over metabolic functions

• This specificity explains why each virus can only invade certain types of cells.

Virus Examples

•HIV – white blood cells• Polio- nerve cells• Adenovirus (cold virus)- adenoid tissue•Hepatitis- liver cells