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Unit 4: Bacteria and Viruses


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Are bacteria alive?
Yes, they reproduce, can adapt, and obtain enrgy and materials.
Are viruses alive?
Yes and No, they carry out all the functions of living things, but only within a host cell.
Binary Fission
Replication of DNA, bacteria cell divides in half.
A bridge forms between two bacteria cells, genes move from one cell to the other.
Voilet and Pink stains are put on the cells. If cell wall has thick peptidoglycan wall stain dark (gram-positive). Gram-negative stay light.
How do you treat bacteria?
Lysogenic Infection
Virus integrates its DNA into the DNA of host cell (using capsid protein), and virus replicates along with host cell.
Lytic Infection
Virus enters cell, makes copies of itself, and causes cell to burst.
Spore Formation
Bacteria produces a thick wall that encloses DNA and part of cytoplasm. When conditions improve, spore will germinate and disappear.
Structure of Bacteria
Cell wall, cell membrane, DNA, ribosomes. NO NUCLEUS.
Three shapes of Bacteria
Bacilli rod-shaped, Cocci spherical, spirilla spiral.
Virus Structure
Core of DNA or RNA surrounded by a protein coat, or capsid.

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