Chapter 19

Bacteria and Viruses

19-1 BacteriaClassifying Prokaryotes

Eubacteria- have cell walls with peptidoglycan, a carbohydrate

Archaebacteria- have cell walls with out peptidoglycan

-DNA is more similar to eukaryotes

-live in harsh environments

Identifying Prokaryotes

• Shape

– Bacilli (rod shaped)

– Cocci (spherical)

– Spirilla (spiral and corkscrew)

Identifying Prokaryotes

• Cell Walls

– Gram-positive: thick peptidoglycan walls

– Gram-negative: think peptidoglycan walls

• More resistant to antibiotics

Identifying Prokaryotes

• Movement

– Some move (flagella)

– Some don’t move

Metabolic Diversity

Heterotrophs

Chemoheterotrophs- get carbon and energy from organic molecules

Ex: humans

Photoheterotrophs- get carbon from organic molecules, get energy from sunlight

Metabolic Diversity

Autotrophs

Photoautotrophs- get carbon from CO2, get energy from sunlight

Ex: cyanobacteria.

Chemoautotrophs- get carbon from CO2, get energy from inorganic chemical reactions

Metabolic Diversity

Carbon Source Energy source

Chemoheterotroph Organic molecules organic molecules

Photoheterotrophs Organic molecules Sunlight

Photoautotrophs Carbon dioxide Sunlight

Chemoautotrophs Carbon dioxide Inorganic chemical reactions

Releasing Energy

• Obligate aerobes- require oxygen

Ex: Mycobacterium tuberculosis

• Obligate anaerobes- do not require oxygen, oxygen kills them

Ex: Clostridium botulinum

• Faculatative anaerobes- live with or w/o oxygen

Ex: E. coli

Growth and Reproduction

• Binary fission- parents splits into two daughter cells, asexual reproduction

Growth and Reproduction

• Conjugation- a pilus forms between two bacteria, DNA is transferred, sexual reproduction

Growth and Reproduction

• Spore Formation-

Endospore- thick wall that protects a dormant bacterium

Importance of Bacteria

• Decomposers

• Nitrogen Fixation

– Taking nitrogen from the air and converting it to a useable form

19-2 Viruses

Virus- composed of a DNA or RNA core surrounded by a capsid (protein coat)

Viral Infection

Lytic Infection- Virus enters the cells, copies itself, and causes the cell to burst

Viral Infection

Lysogenic Infection- virus enters the cell, integrates its DNA into the host DNA, it gets copied when the host replicates

Prophage- viral DNA embedded in a host’s DNA

Retroviruses

• Genetic information is RNA

• In the host RNA is copied to DNA (reverse transcription)

• Examples: HIV

Viroids and Prions

• Viroids- effect plants, ssRNA w/o a capsid

– Damage tomatoes, apples, potatoes

• Prions- effect animals, protein infectious particles

– Ex: mad cow disease, Creutzfeldt-Jakob disease