1. Viruses and Bacteria

2. Viruses Living or Non-Living?
Infectious particles of nucleic acid and proteins
Cannot “live” (reproduce) outside a host

3. History/Discovery
1883 Adolf Mayer sought cause of Tobacco Mosaic Disease
1935- Wendell Stanley crystallized the infectious particle—determined it was NONLIVING (can’t crystallize cells)

4. 1st virus discovered-Tobacco Mosaic Virus (TMV)

5. Virus Structure
Very small and simple (smaller than a ribosome ~20nm in diameter)
Made of DNA or RNA surrounded by a protein coat (capsid)

6. Characteristics
Host specific—identify host cells by “lock and key” fit between proteins on virus and host cell receptors
*Presumed that receptors first evolved because they carried out some functions that benefited the organism

8. Naming Viruses
International Committee on Taxonomy of Viruses names them based on three characteristics:
Type of nucleic acid (DNA or RNA)
Is the nucleic acid double or single stranded
Presence or absence of nuclear envelope

9. Viral Infection
Lytic Infection- virus enters the cell, makes copies of itself, and causes the cell to burst
Lysogenic Infection- virus integrates it DNA into the DNA of the host. Viral DNA replicates with host DNA

10. Viral Reproduction Steps of Lytic Cycle Attachment Entry Replication
Assembly
Lysis/Release (lyses the cell)

13. Retroviruses Contain RNA instead of DNA
Copy their RNA into DNA instead of DNA to RNA
Examples: AIDS, some cancers

14. Bacteria Most numerous and widespread organisms
“Discovered” with the invention of the microscope by Robert Hooke and Anton van Leeuwenhoek (1676)

15. Classification
Two kingdoms of Prokaryotes (Prokaryotes are organisms that lack nuclei or membrane-bound organelles)
Kingdom Eubacteria: “true bacteria” , variety, 3 shapes, no phyla
Kingdom Archaebacteria: “ancient”, lives in extreme environments

16. Archaebacteria
Methanogens–live in large intestines of animals, decompose dead organisms, produce methane gas (CH4)
Halophiles--live in salty environments
Thermoacidophiles—live in hot, acidic environments

17. Size and Structure
1-5 micrometers (much smaller than eukaryotic cells– micrometers)
Unicellular (although grow in colonies)
Prokaryotic- no nucleus, no membrane-bound organelles
* CAN IDENTIFY BACTERIA BASED ON:
Shape, Cell Wall, and Movement

18. Method of Obtaining Energy
Most are heterotrophic (mostly decomposers)
Some are autotrophic—chemotrophs and photoautotrophs
Ex: cyanobacteria

19. Shape Coccus (spherical)* Bacillus (rod-shaped)*
Spirillum (spiral-shaped)*
*Arranged in chains, groups, or pairs
Pair– Diplo-
Chains– Strepto-
Groups– Staphylo—
**Example: Spherical shaped bacteria arranged in chains would be named, “Streptococcus”

22. Cell Wall For Eubacteria only!
Gram negative- thin cell wall consisting of a few layers of peptidoglycan
Gram positive- thick cell wall consisting of many layers of peptidoglycan

23. Typical Bacterial Cell
Cell wall
Cell membranes
DNA (floating freely)-circular chromosome
Ribosomes
Some can move (flagella, others glide)

25. Reproduction Most bacteria reproduce by Binary Fission
Produces 2 identical “daughter” cells
Can grow and divide every 20 minutes
Asexual (no exchange or recombination of genetic information)

26. Image of E. coli going through Binary fission

27. Ways bacteria can accomplish genetic recombination (variation)
Conjugation- exchange of genes from 1 bacterial cell to another
Transformation-bacteria take up pieces of free DNA from another bacterial cell
Transduction- bacteriophage transfer portions of bacterial DNA from one cell to another.

28. E.coli undergoing conjugation

29. “BAD” Bacteria Food Spoilage—smells, makes you sick Bacterial Diseases
Only 3% of all bacteria cause human diseases
Can be treated with antibiotics and prevented through vaccination
1st antibiotic discovered/source
Examples: pneumonia, bubonic plague, Strep. Throat, Syphilis, gonorrhea, anthrax, botulism

30. E. coli

31. “GOOD” Bacteria: The Importance of Bacteria
Decomposers
Help ecosystem recycle nutrients
Breakdown complex compounds into usable materials
Nitrogen fixers
Bacteria perform nitrogen fixation

32. Importance of Bacteria (Cont.)
Human Uses
Production of food and beverages
Medicine and chemical industry
Genetic engineering
Bioremediation: Cleaning up the environment