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Viruses, Bacteria & Archaea - Coggle Diagram
Viruses, Bacteria & Archaea
Lytic Cycle
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The lytic cycle produces new phages and lyses (breaks open) the host’s cell wall, releasing the progeny viruses
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Lysogenic Cycle
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The viral DNA molecule is incorporated into the host cell’s chromosome Phages that use both the lytic and lysogenic cycles are called temperate phages
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Integrated viral DNA
Every time the host divides, it companies the phage DNA and passes the copies to daughter cells
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An environmental signal can trigger the virus genome to exit the bacterial chromosomes and switch to the lytic mode
Some prophages are expressed during lysogeny, and some cause the host bacteria to secrete toxins that are harmful to humans
Bacterial Defenses
Natural selection favors bacterial mutants with surface proteins that cannot be recognized as receptors by a particular type of phage
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Bacterial Appendages
Fimbriae- hairlike appendages that allow them to stick to their substrate or other individuals in a colony
Pili- (sex pili) are longer than fimbriae and function to pull cells together enabling the exchange of DNA
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Oxygen in metabolism
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Obligate anaerobes are poisoned by O2 and live by fermentation or use of substances other than O2 for anaerobic respiration
Facultative anaerobes can use O2 if it is present or carry out fermentation or anaerobic respiration or not
Motility
Texis
About half prokaryotes exhibit taxis, the ability to move toward or away from a stimulus
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Recombinant Cells
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If F- obtains the allele for the F factor from an F positive, the F- cell will become F+, if only a portion of the DNA is transferred the recipient cell will be recombinant
Antibiotics kill most bacteria, but not those with R plasmids, plasmids that carry resistance genes
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Nitrogen metabolism
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Prokaryotes metabolize nitrogen in many forms
For example some prokaryotes convert atmospheric nitrogen (N2) to ammonia (NH3) in a process called nitrogen fixation.
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