Flashcard library · Microbiology
Microbiology: Bacteria & Viruses
Dive into the essential world of Microbiology with this flashcard deck focused on Bacteria and Viruses. This resource covers fundamental structures, life cycles, reproductive strategies, and key distinctions between these microscopic entities. Perfect for students preparing for exams or looking to solidify their understanding of microbial biology and disease.
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What defines a prokaryotic cell?
No membrane-bound nucleus or organelles; its DNA sits in a nucleoid region.
How do Gram-positive and Gram-negative cell walls differ?
Gram-positive: thick peptidoglycan, no outer membrane. Gram-negative: thin peptidoglycan plus an outer membrane with LPS.
How do bacteria reproduce?
Asexually, by binary fission into two identical cells.
What are the three basic bacterial shapes?
Cocci (spheres, e.g., Staphylococcus), bacilli (rods, e.g., E. coli) and spiral forms (e.g., the spirochete Treponema pallidum).
What are bacterial flagella for?
Movement (motility).
What are pili (fimbriae) for?
Attachment to surfaces and cells; sex pili transfer DNA in conjugation.
How do exotoxins differ from endotoxins?
Exotoxins are proteins secreted by many bacteria; endotoxin is the LPS of Gram-negative outer membranes, released mainly when cells lyse.
What are the three ways bacteria exchange genes horizontally?
Transformation (naked DNA), transduction (via bacteriophages) and conjugation (direct cell contact).
What is a virus made of?
DNA or RNA inside a protein capsid, sometimes surrounded by a lipid envelope.
How do the lytic and lysogenic cycles differ?
Lytic: the phage replicates and bursts the cell. Lysogenic: its DNA integrates as a prophage and is copied with the host.
Why are viruses obligate intracellular parasites?
They have no metabolism or ribosomes of their own, so they can only replicate inside host cells.
Why don't antibiotics work against viruses?
Antibiotics hit bacterial targets such as cell walls and ribosomes, which viruses do not have.
Where does a viral envelope come from?
From host cell membrane, picked up as the virus buds out of the cell.
What is a virus's host range?
The cells or species it can infect, set largely by which host receptors it can bind.
Name three ways bacteria resist antibiotics.
Altering the drug's target, making enzymes that inactivate it, and pumping it out with efflux pumps.
What do the beneficial gut bacteria do?
Aid digestion, make vitamins such as K, crowd out pathogens and help regulate the immune system.