Classification

1. Eukaryote Prokaryote Archaebacteria&Bacteria Classification • Old 5 Kingdom system • Monera, Protists, Plants, Fungi, Animals • New 3 Domain system • reflects a greater understanding of evolution & molecular evidence • Prokaryote: Bacteria • Prokaryote: Archaebacteria • Eukaryotes • Protists • Plants • Fungi • Animals

2. Fig. 27-2 2 µm 5 µm 1 µm (a) Spherical (cocci) (b) Rod-shaped (bacilli) (c) Spiral

3. Structure and Function • 3 basic shapes: spherical (cocci), rods (bacillus) and spiral • Cell Wall • Peptidoglycan covers cell, anchors attachments • Archaea have no peptidoglycan

4. Gram Staining Gram + : simple walls, lots of PTG Gram - : complex walls with lipopolysaccharides less PTG • Medical significance: Gram – lipids are toxic causing fever or shock and are resistant to our defenses • Gram –: antibiotic resistance (hard for drugs to penetrate) • Antibiotics often target peptidoglycan

5. 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 peptidoglycan = polysaccharides + amino acid chains lipopolysaccharides = lipids + polysaccharides

6. 200 nm Fig. 27-4 Capsule

7. Sticky and covers entire cell Protection from dehydration and shield from immune system Hair like appendages that stick Ex. Neisseria gonorrhoeae sticks to mucus membranes Shorter and more numerous than sex pilli Capsule vs Fimbriae

8. Fig. 27-5 Fimbriae 200 nm

9. Motility for most bacteria • propel themselves by flagella that are structurally and functionally different from eukaryotic flagella • PROK flagella are 1/10 the width of EUK • PROK flagella are not covered by plasma mem

10. Motility • Different composition and propulsion • The motor of the flagella is the basal apparatus (rings embedded in the cell wall) • ATP proton pump generates power by turning hook attached • Hook is attached to chains of flagellin • In a heterogeneous environment, many bacteria exhibit taxis, the ability to move toward or away from certain stimuli Video: Prokaryotic Flagella (Salmonella typhimurium)

11. Fig. 27-6 Flagellum Filament 50 nm Cell wall Hook Basal apparatus Plasma membrane

12. Chromosome Plasmids Fig. 27-8 1 µm

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

14. Reproduction and Adaptation • Binary fission in optimal conditions every 1-3 hours (E.coli every 20 min usually 1/24 hr) • They are small, repro binary fission and short generation time • Endopsores (ability to endure hardship)

15. Fig. 27-10 EXPERIMENT Daily serial transfer 0.1 mL (population sample) New tube (9.9 mL growth medium) Old tube (discarded after transfer) RESULTS 1.8 1.6 Fitness relative to ancestor 1.4 1.2 1.0 10,000 0 5,000 15,000 20,000 Generation

16. Rapid Evolution: high genetic diversity • 2 strains of E.coli differ in an rRNA gene more than between a human and a platypus • Rapid reproduction • Mutation • Genetic recombination

17. Mutation • Probability of a spontaneous mutation in an E.coli gene is 1 in 10 million/division • 2x1010 new E.coli per day • About 2000 bacteria will have mutations • 4300 genes total in E.coli • 4300 x 2000 = 9 million mutation per day in the human intestines

18. Genetic Recombination • Transformation: uptake foreign DNA • Ex. Competent cells, pneumonia • Transduction: a bacteriophage performs horizontal gene transfer • Conjugation • Plasmids

19. Fig. 27-11-4 Phage DNA A+ B+ A+ B+ Donor cell A+ Recombination A+ A– B– Recipient cell A+ B– Recombinant cell

20. Conjugation and Plasmids • Conjugation is the process where genetic material is transferred between bacterial cells • Sex pili allow cells to connect and pull together for DNA transfer • A piece of DNA called the F factor is required for the production of sex pili • The F factor can exist as a separate plasmid or as DNA within the bacterial chromosome

21. Fig. 27-12 1 µm Sex pilus

22. The F Factor as a Plasmid • Cells containing the F plasmid function as DNA donors during conjugation • Cells without the F factor function as DNA recipients during conjugation • The F factor is transferable during conjugation

23. Fig. 27-13 F plasmid Bacterial chromosome F+ cell F+ cell Mating bridge F– cell F+ cell Bacterial chromosome (a) Conjugation and transfer of an F plasmid Recombinant F– bacterium A+ Hfr cell A+ A+ A+ F factor A– A+ A– A+ A– A– F– cell (b) Conjugation and transfer of part of an Hfr bacterial chromosome

24. R Plasmids and Antibiotic Resistance • R plasmids carry genes for antibiotic resistance • Antibiotics select for bacteria with genes that are resistant to the antibiotics • Antibiotic resistant strains of bacteria are becoming more common

25. Bacterial Diversity Major nutritional modes Role of oxygen in metabolism Nitrogen metabolism nitrogen fixation: converting N2 from the atmosphere into ammonia NH3 Metabolic Cooperation colony of cyanobacterium Anabaena (filaments) genes for photosynthesis (most cells) and N fixation)few heterocytes) but one cell cannot perform both Biofilms

26. Table 27-1

27. Fig. 27-14 Photosynthetic cells Heterocyte 20 µm

28. Prokaryotic phylogeny • Horizontal gene transfer (ring instead of a tree) • Archaea more closely related to eukaryotes than bacteria • polyphyletic Eukarya Archaea Bacteria Eukarya Bacteria Archaea

29. Fig. 27-16 Domain Eukarya Eukaryotes Korarcheotes Euryarchaeotes Domain Archaea Crenarchaeotes UNIVERSAL ANCESTOR Nanoarchaeotes Proteobacteria Chlamydias Spirochetes Domain Bacteria Cyanobacteria Gram-positive bacteria

30. Table 27-2

31. Proteobacteria • These gram-negative bacteria include photoautotrophs, chemoautotrophs, and heterotrophs • Some are anaerobic, and others aerobic

32. Fig. 27-18a Subgroup: Alpha Proteobacteria Alpha Beta Gamma Proteobacteria Delta 2.5 µm Epsilon Rhizobium (arrows) inside a root cell of a legume (TEM) Subgroup: Beta Proteobacteria Subgroup: Gamma Proteobacteria 1 µm 0.5 µm Thiomargarita namibiensis containing sulfur wastes (LM) Nitrosomonas (colorized TEM) Subgroup: Delta Proteobacteria Subgroup: Epsilon Proteobacteria B. bacteriophorus 5 µm 2 µm 10 µm Fruiting bodies of Chondromyces crocatus, a myxobacterium (SEM) Helicobacter pylori (colorized TEM) Bdellovibrio bacteriophorus attacking a larger bacterium (colorized TEM)

33. Subgroup: Alpha Proteobacteria • Many species are closely associated with eukaryotic hosts • Scientists hypothesize that mitochondria evolved from aerobic alpha proteobacteria through endosymbiosis

34. Example: Rhizobium,which forms root nodules in legumes and fixes atmospheric N2 • Arrows in the next slide are Rhizobium • Example: Agrobacterium,which produces tumors in plants and is used in genetic engineering

35. Fig. 27-18c 2.5 µm Rhizobium (arrows) inside a root cell of a legume (TEM)

36. Cyanobacteria • These are photoautotrophs that generate O2 • Plant chloroplasts likely evolved from cyanobacteria by the process of endosymbiosis Two species of Oscillatoria, filamentous cyanobacteria (LM)

37. Concept 27.6: Prokaryotes have both harmful and beneficial impacts on humans • Some prokaryotes are human pathogens, but others have positive interactions with humans • Prokaryotes cause about half of all human diseases • Lyme disease is an example

38. Fig. 27-21 5 µm

39. Pathogenic prokaryotes typically cause disease by releasing exotoxins or endotoxins • Exotoxins cause disease even if the prokaryotes that produce them are not present • Endotoxins are released only when bacteria die and their cell walls break down • Many pathogenic bacteria are potential weapons of bioterrorism