Viruses and Bacteria

Bacterial sizes

• Prokaryotes range from 1-5 μm

• Exception: – Epulopiscium fisheloni is 500 μm!

Classification

• Old system– One kingdom: Monera

• New system– 2 kingdoms

• Eubacteria (Domain Bacteria)• Archaebacteria (Domain Archaea)

Archae is more like us (Eukarya) because we share key genes

Bacteria Shapes

• Bacillus (pl bacilli)– Rod-shaped

• Coccus (pl cocci)– Spherical

• Spirillum (pl spirilla)– Spiral-shaped

Cell Wall

• Gram staining can be used to differentiate bacteria– Thick wall of peptidoglycan—purple color– Thin/no wall—pink/red color

Identify it!

Identify it!

Identify it!

Identify it!

Movement

• Nonmotile• Flagella

Escherichia aurescens

Escherichia coli

Movement

• Spiral movement • Glide on slime

Spirillum volutans Myxobacterium

Metabolism• Bacteria can be either heterotrophic or

autotrophic– Heterotrophic—does not produce own food

source– Autotrophic—does produce own food source

Heterotroph types

• Chemoheterotrophs- take in organic molecules for energy and carbon source– EX: E. coli

• Photoheterotrophs- photosynthetic, but needs organic molecules for a source of carbon

Autotroph types

• Photoautotrophs- use light energy to convert CO2 and water into organic compounds and O2

– EX: cyanobacteria— “blue green algae”• Chemoautotrophs- make organic molecules

from CO2 but use chemical reactions instead of light– Live deep in ocean vents

Releasing energy

• Obligate aerobes—need O2 to live– Ex Mycobacterium tuberculosis

• Obligate anaerobes—die with O2

– Ex Clostridium botulinum• Facultative anaerobes—either or

– Ex E. coli

Growth and Reproduction

• Binary fission—grow, double cellular components, and divide

Growth and Reproduction

• Conjugation– hollow bridge forms so that bacteria can exchange genetic material

Growth and Reproduction

• Spore formation– bacteria can form spores when growth conditions become bad (too hot/cold, too dry, no food)– Protective barrier– When conditions are good again, bacteria will

grow again

Importance of bacteria

• Decomposers-

• Nitrogen Fixers-

• Human uses-

History of Viruses

• Iwanowski and Beijernick (1890’s) – Worked on Tobacco Mosaic Virus (infects tobacco and

tomato leaves). – Creates mosaic pattern on leaves. – Made a juice of the infected leaves and then put this juice

through a filter. Rubbed the filtered juice onto leaves. Still became infected. Concluded that whatever these disease causing particles were, they were very small (smaller than bacteria).

• Named them viruses meaning “poison”.

History of Viruses

• Stanley (1935) – Purified TMV into a crystal. – Living particles don’t crystallize therefore, viruses

are non-living pathogenic (disease causing) particles.

Viruses

• Particles of nucleic acid, protein and sometimes a lipid envelope.

• Obligate intracellular parasite (can only replicate within a living cell)

Structure of a Virus

• Small – 20nm (polio virus) – 350nm (small pox virus)• Single type of nucleic acid (RNA or DNA but never

both)• Protein coat – capsid• Some have envelopes (made of lipids)outside of

capsid• Surface projections made up of lipids for attachment

onto host cells• Are specific to their host

Structure of a Virus

Viral Shapes

• Shapes are – Rod– Helical– Icosahedral (20 sides)

Viruses

• Particles of nucleic acid, protein and sometimes a lipid envelope.

• Obligate intracellular parasite (can only replicate within a living cell)

Bacteriophage

• Infect E. coli bacteria

• Attach with tail fibers onto cell.

• Inject nucleic acid into cell

The Lytic Cycle• Get in, replicate and get out to invade other host cells• Virulent (Disease causing)• The cold, rubella (German measles), mumps

ReleaseAttachment at Receptor site

Entry

Replication

Assembly

The Lytic Cycle of Virus infection

Attaches onto host cell Injects DNA into host cell Replication of Viral parts

Reassembly of virons Lysis – bursting out

Viruses that reproduce only by the lytic cycle are called Virulent

Lysogenic Infection• Virus embeds its DNA into hosts DNA which is replicated

with host cell’s DNA. • Remains unnoticed for sometimes years• AIDS, cold sores, chicken pox, hepatitis

Prophage

Attachment Integration Cell multiplication & Injection of nucleic acid Prophage remains unnoticed and not transcribed

Viral Diseases

• Measles, Mumps, Rubella, Rabies, the Cold, the Flu, Influenza, Hepatitis, AIDS, Chicken pox, Small pox, Polio, Yellow fever, Meningititis, some cancers

• Vaccines are small doses of either killed, altered or live viruses. Body builds up antibodies against virus

Diseases Caused by Viruses• AIDS• The Cold• Measles• Mumps• Rubella• Chicken pox/Shingles• Small Pox• Hepatitis• SARS• The Flu• Ebola• HPV• Bird Flu• Polio

The Different Forms of Viruses• Retroviruses – AIDS. Contains RNA instead of DNA.

Goes from RNA to DNA to RNA to protein. Normal is DNA to RNA to protein.

• Viroids – another disease causing agent but no capsid, only the RNA. – Found only in plants

• Prion – viral proteins that cause diseases. Scrapie in sheep degrades nervous system. Mad Cow disease (Bovine spongiform encephalopathy) in cows – puts holes into brain.– In humans, its Creutzfeld-Jakob disease & Kuru.

Diseases Caused by Bacteria and Viruses

1. What is a pathogen?

2. Okay, now the bad. Name the two ways bacteria cause disease in living organisms.

3. How can bacterial diseases be prevented?

4. How can they be treated?

5. Make a list of human diseases caused by bacteria.

6. What does it mean to sterilized a substance?

7. How can we prevent bacteria from spoiling our food?

8. What do viruses do to us to produce disease?

9. How are viral diseases treated and prevented?

10.What is non-effective at treating viral diseases?

11.List 9 diseases caused by viruses in humans

12.How are most plant diseases spread?

13. What is a prion? 14. Why are viruses not considered to be alive?