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Chapter 27 Bacteria & Archaea.

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1 Chapter 27 Bacteria & Archaea

2 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

3 Gram Staining - + More complex, less peptidoglycan, outer layer of lipopolysaccharides Simpler cell wall, large amounts of peptidoglycan

4 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.

5 Bacteria Locomotion Flagella Slimmer than Eukaryotic flagella Not covered by plasma membrane as Eukaryotic flagella a Different molecular composition and Eukaryotic flagella Mechanism of propulsion is different than Eukaryotic

6 Taxis – movement towards or away from a stimulus
Positive taxis – towards stimulus Negative taxis – away from stimulus Examples: Chemotaxis Phototaxis

7 Transformation – pGLO lab – genotype and
Transformation – pGLO lab – genotype and possibly phenotype is changed by the uptake of foreign DNA from its surroundings. pGLO Griffins experiment Transduction – Bacteriophages (viruses) carry bacterial genes from one host cell to another (accidents during viral replication)

8 Conjugation – DNA transfer from. one bacterial cell to another
Conjugation – DNA transfer from one bacterial cell to another (same or different species) Binary Fission – asexual reproduction of bacteria

9 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

10 Transformation Transduction Conjugation
Questions from 27.2 pg. 564 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. Distinguish between the three mechanisms of transferring DNA from one bacterial cell to another. Transformation Transduction Conjugation 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.

11 Photoautotroph vs. Chemoautotroph
Energy source is light Energy source is inorganic compounds (H2S or NH3) Photoheterotroph vs. Chemoheterotrophs Energy source is light Energy source is organic but obtain carbon in organic form compounds and obtain carbon in organic form (animals, fungi, and most protists)

12 The role of Oxygen in metabolism
1. Obligate Aerobes – use O2 for CR, can’t live wo/it 2. Obligate Anaerobes – poisoned by O2, some live by fermentation while others go through anaerobic respiration using nitrate ions or sulfate ions 3. Facultative Anaerobes – use O2 if it is present but can also carry out anaerobic respiration or fermentation if needed Nitrogen fixation – converting atmospheric nitrogen to ammonia (NH3) Benefit: can then use ammonia to make amino acids and nucleotides

13 Filamentous colonies – cooperation between the same species
majority of cells in the colony carry out photosynthesis there are a few cells (“heterocytes”) that carry out nitrogen fixation (have a thicker cell wall to keep O2 out) cells can’t do both because the O2 inactivates the enzymes involved in nitrogen fixation. products from both reactions get transported via intercellular connections between the cells Biofilms – cooperation between different species cells in colony secrete signaling molecules that recruit nearby cell. cells also produce proteins that stick the cells together and to a substrate. channels wi/biofilm allow nutrients and waste to be transported Causes of tooth decay, damage to industrial and medical equipment, contamination of products

14 Ecological Significance of Prokaryotes:
Recycling: Symbiosis: Pathogens: Bioremediation: Genetic Engineering Identify 2 ways Prokaryotes have affected you positively today…


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