Exploring Prokaryotes: Origins, Diversity, and Metabolism

1. Prokaryotes and Origin of Metabolic Diversity AP Biology Crosby High School

2. A World of Prokaryotes • Your mouth • They are more infamous than famous • Two types • Archaea: Origin from the first cell • Bacteria: More recent • Differ in structural, biochemical, and physiological • Carl Woese

3. Cell Shapes • Cocci • Spherical • Bacillus • Rod • Spirilla and Spirochetes • Size range • 1-5 µm • Largest is .75 mm

4. Bacterial Cell Walls • Composed of peptidoglycans • Form a capsule to protect from host defenses • Gram stains • Gram-positive (Purple) • Simpler walls • Large amt. Peptidoglycans • Gram-negative (Pink) • Contain lipopolysaccharides • Generally more threatening

5. Prokaryotic Motility • Flagella • 1/10 width of Eu. • Not covered by membranous extension • Spirochetes • Flagella-like connected to basal motor • Corkscrew motion • Slime Secretions • Taxis: Movement toward or away from stimulus

6. Cellular and Genomic Organization • Lack Compartmentalization • 1/1000 as much DNA as Eu. • May contain Plasmids • Can survive w/o Plasmids • Give resistance to antibiotics • Replicate independently of genophore

7. Prokaryotic Reproduction • Binary Fission • Gene transfer • Transduction: Viruses transfer genes • Conjugation: Direct transfer of genes • Transformation: Takes genes from surrounding environment • Generations take minutes – hours

8. Growth and Protection • Geometric “Growth” • Limitations of growth • Nutrient exhaustion • Metabolic waste • Endospore • Cell Replicates its chromosomes • One copy is surrounded by a durable wall • Autoclaves needed to kill endospores

9. Prokaryotic Nutrition • Photoautotrophs • Light and Carbon Dioxide • Cyanobacteria • Chemoautotrophs (Pro. Only) • Carbon dioxide for Carbon source • H2S, NH3, Fe2+ • Photoheterotrophs (Pro. Only) • Light for ATP, but needs a Carbon source • Chemoheterotrophs • Consume organic molecules for both energy and carbon source

10. Nutritional Diversity • Saprobes: Decomposers • Parasites: Absord nutrients from living host body fluid • Specificity • Lactobacillus: • Require all 20 a.a. • Several vitamins • E. coli: • Glucose or some other substitute

11. Nitrogen Metabolism • Nitrosomes: convert NH4+ to NO2- • Pseudomonas: “Denitrify” NO2- or NO3- to N2 for atmosphere • Cyanobacteria: • use atmospheric nitrogen directly • Nitrogen Fixation: N2 NH4+ • Nitrogen – fixing cyanobacteria are most self-sufficient form of life

12. Oxygen and Metabolism • Obligate Aerobes • Use O2 for cellular respiration • Obligate Anaerobes • Poisoned by O2 • Live mostly by fermentation • Partly by Anaerobic respiration • Facultative Anaerobes • Use O2 if present • Fermentation if no O2

13. Photosynthesis Evolved Early • Glycolysis was probably among the first metabolic pathways • Photosynthesis likely evolved only once and very early • Cyanobacteria are the only prokaryotic photoautotrophs that release O2 by splitting H2O

14. Archaea Kingdoms • Most sorted into Euryarchaeota or Crenarchaeota • Extremophiles • Methanogens (Eury) • CO2 + H2 CH4 • Strictest anaerobes live in swamps • Extreme Halophiles (Eury) • Purple-red scum due to bacteriorhodopsin • Extreme Thermophiles (Cren) • Generally 60-80 °C but up to 105 °C in deep sea vents • Sulfolobus in Yellowstone

15. Bacteria Kingdoms • Proteobacteria • Alpha • Closely associated with Eukarya • i.e. Rhizobium, Agrobacterium, Rickettsias, Mitochondria • Beta • Nitrosomonas: NH4+ NO2- • Gamma • i.e. Chromatium, Legionella, Salmonella, Vibrio cholerae, Escherichia coli

16. Bacterial Kingdoms (cont.) • Proteobacteria (cont.) • Delta • Myxobacteria • Secretes a slimy substratum to glide along • When soil is dry it produces “fruiting” bodies • Releases spores to form new colonies • Bdellovibrio • Charges prey at 100 µm/sec • Drills by spinning at 100 rps • Epsilon • Helicobacter pylori: stomach ulcers

17. Bacterial Kingdom (cont. cont.) • Chlamydias • Gram-negative w/o peptidoglycans • Chlamydia trachomatis: causes blindness and nongonococcal urethritis • Spirochetes • Treponema pallidum: Syphilis • Borrelia burgdorferi: Lyme disease

18. Bacteria Kingdoms (will they ever end?) • Gram-Positive Bacteria • Actinomycetes • Tuberculosis and leprosy • Spore formers • Bacillus anthracis • Clostridium botulinum • Staphylococcus and Streptococcus • Mycoplasmas • Smallest of all living cells and lack cell walls • Cyanobacteria: only bacterium with plantlike oxygenic photosynthesis

19. Prokaryotes and Our World • Decomposers: release C, N, and other elements back into the ecosystem • Producers: Provide the base for many food chains • Symbiosis • Mutualistic: Both members benefit • Commensalistic: One member benefits • Parasitic: Parasite benefits while host suffers

20. Human Diseases as a Result of Prokaryotes • Opportunistic • Koch’s Postulate • Find the same pathogen in every diseased individual • Isolate same pathogen and grow microbe in pure culture • Induce disease in experimental animal from culture • Isolate same pathogen from infected animal

21. Toxins • Exotoxins: Proteins secreted by pro. • 1g of Botulism can kill a million people • Endotoxins • Components of outer membrane of gram-neg. bacteria • Antibiotics • Biological Warfare

22. Human Uses • Bioremediation: • Organisms are used to remove pollutants from the air, water and soil • Sewage treatment facilities • Mass Production • Insulin production

23. Cyanobacteria

24. Streptomyces and Mycoplasmas

25. Leptospira

26. Chlamydias

27. Helicobacter pylori

28. Myxobacteria and Bdellovibrio

29. Chromatium

30. Rhizobium

31. Photosynthetic Parsimony

32. Gram Stains