BIOL 1111 Lecture Notes - Lecture 5: Crystal Violet, Horizontal Gene Transfer, Antimicrobial Resistance
13 Jun 2018
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Chapter 22- Bacteria and Archaea
-Archaea and bacteria=prokaryotes
Prokaryotic Cellular Structure
-small but plenty; greatest biomass, very
diverse
-common shapes: spiral, spherical
(coccoid), cylindrical (rod)
-uncommon shape: square
-cell wall, plasma membrane, nucleoid
(DNA concentrated in one region),
ribosomes scattered throughout, no
organelles
Prokaryotic chromosomes: single,
circular DNA molecule packed into nucleoid (no nucleolus and no nuclear
membrane)
Plasmids: small circles of DNA, genes supplement nucleoid genes (ex.
Antibiotic resistance); replicate independently
-transfer DNA between the two happens using Horizontal Gene Transfer
Prokaryotic Ribosomes
Bacterial ribosomes: smaller than eukaryotic ribosomes, but similar protein synthesis to eukaryotes
Archaeal ribosomes: different structure, protein synthesis is a combination of bacterial and eukaryotic
processes
Prokaryotic Cell Wall
-peptidoglycan is primary component (polymer of sugars and amino acids in a chain)
-the peptide cross linkages between chains gives the cell wall strength and rigidity; provides shape and
protection
-penicillin prevents peptide cross-linkage formation (inhibitor of the enzyme use to create
peptidoglycan)
Gram Stain
-based on cell wall thickness
-stain with crystal violet, rinse with ethanol and counterstain with safranin
Gram positive bacteria: appear purple because crystal violet retained (thick peptidoglycan wall/layer)
Gram negative bacteria: appear pink because crystal violet lost (thin peptidoglycan sheath surrounded
by outer membrane- acts as a barrier for crystal violet)
Capsule
-not all bacteria have this
-a sticky layer of polysaccharides surrounding the cell wall
-protects bacteria from extreme temperatures, desiccation, antibiotics, viruses, and
antibodies
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Document Summary
Cell wall, plasma membrane, nucleoid (dna concentrated in one region), ribosomes scattered throughout, no organelles. Prokaryotic chromosomes: single, circular dna molecule packed into nucleoid (no nucleolus and no nuclear membrane) Plasmids: small circles of dna, genes supplement nucleoid genes (ex. Transfer dna between the two happens using horizontal gene transfer. Bacterial ribosomes: smaller than eukaryotic ribosomes, but similar protein synthesis to eukaryotes. Archaeal ribosomes: different structure, protein synthesis is a combination of bacterial and eukaryotic processes. Peptidoglycan is primary component (polymer of sugars and amino acids in a chain) The peptide cross linkages between chains gives the cell wall strength and rigidity; provides shape and protection. Penicillin prevents peptide cross-linkage formation (inhibitor of the enzyme use to create peptidoglycan) Stain with crystal violet, rinse with ethanol and counterstain with safranin. Gram positive bacteria: appear purple because crystal violet retained (thick peptidoglycan wall/layer)
