Presentation on theme: "How do bacterial cell walls differ from plant cell walls? Plants – made of cellulose (polysaccharide) Bacteria – made of peptidoglycan Archaea – lack."— Presentation transcript:
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
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 flagella Not covered by plasma membrane as Eukaryotic flagella a Different molecular composition and Eukaryotic flagella Mechanism of propulsion is different than Eukaryotic
Taxis – movement towards or away from a stimulus Positive taxis – towards stimulus Negative taxis – away from stimulus Examples: Chemotaxis Phototaxis
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)
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 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 Transduction Conjugation 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.
Photoautotrophvs.Chemoautotroph Energy source is lightEnergy source is inorganic compounds (H 2 S or NH 3 ) Photoheterotrophvs.Chemoheterotrophs Energy source is lightEnergy source is organic but obtain carbon in organic formcompounds and obtain carbon in organic form (animals, fungi, and most protists)
The role of Oxygen in metabolism 1. Obligate Aerobes – use O 2 for CR, can’t live wo/it 2. Obligate Anaerobes – poisoned by O 2, some live by fermentation while others go through anaerobic respiration using nitrate ions or sulfate ions 3. Facultative Anaerobes – use O 2 if it is present but can also carry out anaerobic respiration or fermentation if needed Nitrogen fixation – converting atmospheric nitrogen to ammonia (NH 3 ) Benefit: can then use ammonia to make amino acids and nucleotides
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 O 2 out) cells can’t do both because the O 2 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
Ecological Significance of Prokaryotes: Recycling: Symbiosis: Pathogens: Bioremediation: Genetic Engineering Identify 2 ways Prokaryotes have affected you positively today…