AP Biology

1. AP Biology Lecture #46 Prokaryotes

2. Domain Bacteria Domain Archaea Domain Eukarya Common ancestor Prokaryotes Domain Bacteria Domain Archaebacteria

3. Bacteria • Bacteria are classified into two kingdoms: Eubacteria (true bacteria) and Archaebacteria (Ancient Bacteria). • BACTERIA are microscopic Prokaryotes.  (“before nucleus”) • Adapted to living in all environments (even some extreme) – they exist EVERYWHERE

4. Bacteria live EVERYWHERE! • Bacteria live in all ecosystems • on plants & animals • in plants & animals • in the soil • in depths of the oceans • in extreme cold • in extreme hot • in extreme salt • on the living • on the dead Microbes alwaysfind a way tomake a living!

5. Bacterial diversity Rods(bacilli) and spheres(cocci) and spirals(helical)…Oh My!

6. eukaryote cell prokaryotecell Prokaryote Structure • Unicellular • bacilli, cocci, spirilli • Size • 1/10 size of eukaryote cell • 1 micron (1μm) • Internal structure • no internal compartments • no membrane-bound organelles • only ribosomes • circular chromosome, naked DNA • not wrapped around proteins

7. Shapes of Bacteria • Coccus • Chain = Streptoccus • Cluster = Staphylococcus • Bacillus • Chain = Streptobacillus • Coccobacillus • Vibrio = curved • Spirillum • Spirochete • Square • Star

9. mitochondria chloroplast Variations in Cell Interior cyanobacterium(photosythetic) bacterium aerobic bacterium internal membranesfor respirationlike a mitochondrion(cristae) internal membranesfor photosynthesislike a chloroplast(thylakoids)

11. Bacterial Structures • Flagella • Pili • Capsule • Plasma Membrane • Cytoplasm • Cell Wall • Lipopolysaccharides • Teichoic Acids • Inclusions • Spores

12. Bacteria Structure Flagella is used for movement Pilli (Fimbrae) help bacteria cling to surfaces Prokaryotes do not have organelles or a membrane bound  nucleus! Nucleoidregion contains a circular loop of DNA Plasmids are rings of DNA, used in reproduction Ribosomesin cytoplasm synthesize proteins

13. outer membrane of lipopolysaccharides Gram-negative bacteria Gram-positive bacteria peptide side chains outer membrane cell wall peptidoglycan cell wall peptidoglycan plasma membrane plasma membrane protein Prokaryote Cell Wall Structure That’simportant foryour doctorto know! peptidoglycan = polysaccharides + amino acid chains lipopolysaccharides = lipids + polysaccharides

14. Motility • 1- Flagella • 2- Helical shape (spirochetes) • 3- Slime • 4-Taxis (movement away or toward a stimulus)

15. Flagella • Motility - movement • Swarming occurs with some bacteria • Spread across Petri Dish • Proteus species most evident • Arrangement basis for classification • Monotrichous; 1 flagella • Lophotrichous; tuft at • one end • Amphitrichous; both • ends • Peritrichous; all around • bacteria

16. Form & Function • Nucleoid region (genophore: non-eukaryotic chromosome) • Plasmids • Asexual reproduction: binary fission (not mitosis) • “Sexual” reproduction (not meiosis): • transformation~ uptake of genes from surrounding environment • conjugation~ direct gene transfer from 1 prokaryote to another transduction~ gene transfer by viruses • Endospore: resistant cells for harsh conditions (250 million years!)

17. Bacteria can reproduce sexually by conjugation or asexually by binary fission.

18. In bacteria, genetic recombination can occur in three ways. a. Conjugation occurs when a bacterium passes DNA to a second bacterium through a tube (sex pilus) that temporarily joins two cells; this occurs only between bacteria in the same or closely related species. b.Transformation involves bacteria taking up free pieces of DNA secreted by live bacteria or released by dead bacteria. c. In transduction, bacteriophages transfer portions of bacterial DNA from one cell to another. Plasmids can carry genes for resistance to antibiotics and transfer them between bacteria by any of these processes

19. Genetic variation in bacteria • Mutations • bacteria can reproduce every 20 minutes • binary fission • error rate in copying DNA • 1 in every 200 bacteria has a mutation • you have billions of E. coli in your gut! • lots of mutation potential! • Genetic recombination • bacteria swap genes • plasmids • small supplemental circles of DNA • conjugation • direct transfer of DNA conjugation

20. Plasmid – an extra bit of DNA, used in sexual reproduction Plasmids are also used in genetic engineeringSome bacteria form resistant endospores in response to unfavorable environmental conditions.

21. Nutrition & Metabolism • Photoautotrophs: photosynthetic; harness light to drive the synthesis of organics (cyanobacteria) • Chemoautotrophs: oxidation of inorganics for energy; get carbon from CO2 • Photoheterotrophs: use light to generate ATP but get carbon in an organic form • Chemoheterotrophs: consume organic molecules for both energy and carbon • saprobes-dead organic matter decomposer • parasites-absorb nutrients from living hosts • Oxygen relationships: obligate aerobes; facultative anaerobes; obligate anaerobes

22. Bacteria classified as heterotrophs derive energy from breaking down complex organic compoundsin the environment. This includes saprobes, bacteria that feed on decaying material and organic wastes, as well as those that live as parasites, absorbing nutrients from living organisms.

23. Prokaryotic Nutrition 1.   Bacteria differ in their need for, and tolerance of, oxygen (O2). a.   Obligate anaerobes are unable to grow in the presence of O2; this includes anaerobic bacteria that cause botulism, gas gangrene, and tetanus. b.   Facultative anaerobes are able to grow in either the presence or absence of gaseous O2. c.   Aerobic organisms (including animals and most prokaryotes) require a constant supply of O2 to carry out cellular respiration. staphylococcus is a gram-positive, facultative anaerobe

24. 2.   Autotrophic Prokaryotes a.   Photoautotrophs are photosynthetic and use light energy to assemble the organic molecules they require. b.   Chemoautotrophs make organic molecules by using energy derived from the oxidation of inorganic compounds in the environment. (methanogens)

25. 3.   Heterotrophic Prokaryotes a.    Most free‑living bacteria are chemoheterotrophsthat take in pre-formed organic nutrients. b.    As aerobicsaprotrophs, there is probably no natural organic molecule that cannot be broken down by some prokaryotic species. c.    Detritivores (saprophytic bacteria)are critical in recycling materials in the ecosystem; they decompose dead organic matter and make it available to photosynthesizers. Bacteria have an important role to play in breaking down materials in the environment. Some are harmful and break down material we'd rather keep, like this image of an infection of necrotizing fasciitis (flesh-eating bacteria)

26. Endospore • Bacteria can survive unfavorable conditions by producing an endospore.

27. Bacteria as pathogens • animal diseases • tooth decay, ulcers • anthrax, botulism • plague, leprosy, “flesh-eating” disease • STDs: gonorrhea, chlamydia • typhoid, cholera • TB, pneumonia • lyme disease plant diseases • wilts, fruit rot, blights opportunistic: normal residents of host; cause illness when defenses are weakened •Koch’s postulates: criteria for bacterial disease confirmation •exotoxins: bacterial proteins that can produce disease w/o the prokaryote present (botulism) •endotoxins: components of gram - membranes (Salmonella)

28. The Gram Stain Gram's Crystal iodine violet Decolorise with acetone Gram-positives appear purple Counterstain with e.g. methyl red Gram-negatives appear pink

29. Bacteria as beneficial (& necessary) • Life on Earth is dependent on bacteria • decomposers • recycling of nutrients from dead to living • nitrogen fixation • only organisms that can fix N from atmosphere • needed for synthesis of proteins & nucleic acids • plant root nodules • help in digestion (E. coli) • digest cellulose for herbivores • cellulase enzyme • produce vitamins K & B12 for humans • produce foods & medicines • from yogurt to insulin

30. Archaebacteria • Methane producers – anaerobic • Halophiles • Halo = salt • Philia = love • Thermophiles • Thermo = heat

31. Methanogens • These Archebacteria are anaerobes. They make methane (natural gas) as a waste product. They are found in swamp sediments, sewage, and in buried landfills. In the future, they could be used to produce methane as a byproduct of sewage treatment or landfill operation.

32. Extreme halophiles can live in extremely salty environments. Most are photosynthetic autotrophs. The photosynthesizers in this category are purple because instead of using chlorophyll to photosynthesize, they use a similar pigment called bacteriorhodopsin that uses all light except for purple light, making the cells appear purple.

33. These are Archaebacteria from hot springs and other high temperature environments. Some can grow above the boiling temperature of water. They are anaerobes, performing anaerobic respiration. Thermophiles are interesting because they contain genes for heat-stable enzymes that may be of great value in industry and medicine.