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!

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 CO 2 and water into organic compounds and O 2 – EX: cyanobacteria— “blue green algae” Chemoautotrophs- make organic molecules from CO 2 but use chemical reactions instead of light – Live deep in ocean vents

Releasing energy Obligate aerobes—need O 2 to live – Ex Mycobacterium tuberculosis Obligate anaerobes—die with O 2 – 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 Release Attachment at Receptor site Entry Replication Assembly

The Lytic Cycle of Virus infectionLytic Cycle 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?