Chapter 27 Bacteria & Archaea

How do bacterial cell walls differ from plant cell walls?Plants – made of cellulose (polysaccharide)

Bacteria – made of peptidoglycan

Archaea – lack peptidoglycan, made of a variety of polysaccharides and proteins

GRAM STAINING

Simpler cell wall, large amounts of peptidoglycan

+-

More complex, less peptidoglycan, outer layer of lipopolysaccharides

Capsule – sticky layer of polysaccharide or protein covering the cell wall of many prokaryotes

enables them to adhere to substrate or other cells (colony)

prevent dehydration protects from host’s immune system

Fimbriae – hair-like protein appendages (aka “attachment pili”)

Sex pili – appendages that pull two cells together prior to DNA transfer from one cell to the other.

Bacteria Locomotion

Flagella Slimmer than Eukaryotic flagellaNot covered by plasma membrane as Eukaryotic flagella aDifferent molecular composition and Eukaryotic flagellaMechanism of propulsion is different than Eukaryotic

Taxis – movement towards or away from a stimulus

Positive taxis – towards stimulusNegative taxis – away from stimulus

Examples:ChemotaxisPhototaxis

Transformation – pGLO lab – genotype and possibly phenotype is changed by the uptake of foreign DNA from its surroundings.

pGLOGriffins experiment

Transduction – Bacteriophages (viruses) carry bacterial genes from one host cell to another (accidents during viral replication)

Conjugation – DNA transfer from one bacterial cell to another (same or different species)

Binary Fission – asexual reproduction of bacteria

What is the difference between and F plasmid and an R plasmid?F plasmid – contains genes that enable cell to form a “mating bridge” with a cell that does not have the plasmid.

R plasmid – contains genes that make it resistant to antibiotics

What is the difference between F+ cells and F- cells?F+ cells contain the F plasmid and therefore are donors during conjugation

F- cells do not contain the F plasmid and therefore are recipients during conjugation

Questions from 27.2 pg. 564

1. What features of prokaryotes make it likely that considerable genetic variation will be added to their populations in each generation?

Large population size (more likely that more individuals will have new mutations at any particular gene…adding diversity)

Short generation time.

2. Distinguish between the three mechanisms of transferring DNA from one bacterial cell to another.

Transformation TransductionConjugation

3. If a nonpathogenic bacterium were to acquire resistance to antibiotics, could this strain pose a health risk to people? Explain.

Yes. Genes for antibiotic resistance could be transferred from the nonpathogenic bacterium to a pathogenic bacterium, which could then harm the population. (MRSA). The processes listed in #2 increase the spread of resistance genes.