1. Prokaryotes and Viruses
Adapted from presentation by Stephanie Bolton, White County High School, Georgia

2. Microorganisms
Single-celled organisms that are too small to be seen without a microscope
Bacteria are the smallest living organisms
Viruses are smaller but are not alive

3. The Prokaryotes Only two groups Archaebacteria and Eubacteria
Arose before the eukaryotes

4. Prokaryotic Characteristics
No membrane-bound nucleus
Single chromosome
Cell wall (in most species)
Prokaryotic fission
Metabolic diversity

5. Prokaryotic Body Plan Figure 21.3 Page 348 DNA capsule plasma membrane
ribosomes in cytoplasm
bacterial flagellum
pilus
cell wall
cytoplasm

6. Bacterial Shapes
coccus
bacillus
spirillum
In-text figure Page 348

7. Bacterial Genes Bacteria have a single chromosome
Circular molecule of DNA
Many bacteria also have plasmids
Self-replicating circle of DNA that has a few genes
Can be passed from one cell to another

8. Prokaryotic Fission - 1 Bacterium before bacterial chromosome
DNA replication
bacterial chromosome
DNA replication
begins
Figure 21.7
Page 350

9. DNA replication completed Membrane growth moves DNA molecules apart
Prokaryotic Fission - 2
parent DNA molecule
DNA copy
DNA replication completed
Membrane growth moves DNA molecules apart
Figure 21.7
Page 350

10. New membrane and cell-wall material deposited Cytoplasm divided in two
Prokaryotic Fission - 3
New membrane and cell-wall material deposited
Cytoplasm divided in two
Figure 21.7
Page 350

11. Conjugation Transfer of plasmid Figure 21.8 Page 351 nicked plasmid
in donor cell
conjugation tube
to recipient cell
Conjugation
Transfer of plasmid
Figure 21.8 Page 351

12. Prokaryotic Classification
EUBACTERIA
(Bacteria)
ARCHAEBACTERIA
(Archaea)
EUKARYOTES
(Eukarya)
Traditionally classified by numerical taxonomy
Now increased use of comparative biochemistry
Figure 21.9 Page 351

13. Archaebacteria
Methanogens-live in oxygen free habitats (form methane gas as a biproduct) Extreme halophiles- can survive in extreme salt Extreme thermophiles- can survive extreme heat WHERE MIGHT WE FIND THESE TODAY?

14. Eubacteria Includes most familiar bacteria
Most have cell wall; always includes peptidoglycan
Classification based largely on metabolism

15. Eubacteria cont.

16. Metabolic Diversity
Photoautotrophs- use light & inorganic carbon dioxide to make organic compounds. (like plants)
Photoheterotrophs- use light & obtain carbon from ORGANIC sources. (halophiles)
Chemoautotrophs- Use chemicals as energy source + inorganic carbon dioxide.
Chemoheterotrophs-must consume organic compounds to get energy & carbon. (Most common)

17. Some Pathogenic Eubacteria
Most are chemoheterotrophs/decomposers
E. coli strains
Clostridium botulinum
Clostridium tetanus
Borrelia burgdorferi
Rickettsia rickettsii

18. Bacterial Behavior Bacteria move toward nutrient-rich regions
Aerobes move toward oxygen; anaerobes avoid it
Photosynthetic types move toward light
Magnetotactic bacteria swim downward
Myobacteria show collective behavior

19. Virus Noncellular infectious agent
Protein wrapped around a nucleic acid core
Cannot reproduce itself; can only be reproduced using a host cell

20. Viral Body Plans Complex virus (bacteriophage) Helical virus
Genetic material is DNA or RNA (not both)
Coat is protein
Helical virus
Polyhedral virus
Fig Page 356

21. Enveloped Virus (HIV) viral protein lipid envelope (derived from host)
viral RNA
reverse transcriptase
Fig Page 356
viral coat (proteins)

22. Viral Multiplication - Basic Steps
Attach to host cell
Enter host (virus or just genetic material)
Direct host to make viral genetic material and protein
Assemble viral nucleic acids and proteins
Release new viral particles

23. Lysis of host cell is induced; infectious particles escape.
Lytic Pathway
Tail fibers and other parts are added to coats.
Virus particles bind to wall of suitable host. Viral genetic material enters cell cytoplasm.
Viral protein molecules are assembled into coats; DNA is packaged inside.
Viral DNA directs host machinery to produce viral proteins and viral DNA.
Stepped Art Fig Page 358

24. Viral DNA usually becomes integrated into the bacterial chromosome.
Lysogenic Pathway
Viral DNA is excised from chromosome and cell enters lytic pathway.
Prior to prokaryotic fission, the chromosome and integrated viral DNA are replicated.
After binary fission, each daughter cell will have recombinant DNA.
Stepped Art Fig (2) Page 358

25. Viroids Smaller than viruses Strands or circles of RNA
No protein-coding genes
No protein coat
Cause many plant diseases

26. Prions Small proteins Linked to human diseases Animal diseases Kuru
Creutzfeldt-Jakob disease (CJD)
Animal diseases
Scrapie in sheep
Bovine spongiform encephalopathy (mad cow disease)

27. Nature of Disease
Contagious disease pathogens must directly contact a new host
Epidemic
Pandemic (AIDS)
Sporadic
Endemic

28. Evolution and Disease Host and pathogen are coevolving
If a pathogen kills too quickly, it might disappear along with the individual host
Most dangerous if pathogen
Is overwhelming in numbers
Is in a novel host
Is a mutant strain

29. New Threats Emerging Pathogens Drug-resistant strains Food poisoning
Ebola virus
Monkeypox virus
Drug-resistant strains
Food poisoning
E. coli
Salmonella