Evolution of Microbial Life: Prokaryotes and Protista

1. Evolution of Microbial Life: Prokaryotes and Protista • Prokaryotes • Bacteria • Archaea • Protists

2. Prokaryotes have inhabited earth for billions of years • Fossil record shows prokaryotes abundant 3.5 bya • Currently, collective biological mass is at least 10 times that of eukaryotes • There are tens of thousands of species (many of which have not been described)

3. Prokaryotes come in a variety of shapes • Coccus: spherical • Streptococcus, staphloylococcus • Bacillus: rods • Spirillum: curly Q

4. Prokaryote External Structures • Gram + • Simple walls with thick peptidoglycan • Gram – • Complex walls with little peptidoglycan, outer membrane

5. Prokaryote External Structures • Capsule • Sticky layer of polysaccharides • Fimbriae • Hairlike appendages, help anchor bacteria • Motility: • Many have flagella (lacks microtubules)- protein structure

6. Reproduction and Adaptation • Most reproduce in 1-3 hours • Some can form endospore: protection in harsh environment (Bacillus anthracis)- can remain dormant for centuries

7. Internal Organization • Some have specialized membranes that perform metabolic functions • Circular DNA, different ribosomes, etc.

8. Autotrophs • Produce their own carbon molecules • Photoautotrophs: photosynthesis • Chemoautotrophs: inorganic chemicals

9. Heterotrophs • Obtain carbon from other sources • Photoheterotrophs: can do photosynthesis • Chemoheterotrophs: obtain energy and carbon from exterior sources

11. Prokaryotes obtain nourishment in a variety of ways • Some are individualists (obtain their own food, energy) • Some are cooperative (some cells perform some processes, while other cells perform other processes) • Biofilms: cells in a colony adhere to each other and their substrate (function as one) • Some cross-species cooperation possible

13. Prokaryotes help clean up the environment • Natural situations: many prokaryotes recycle nitrogen, etc. through natural systems • Bioremediation: remove pollutants from soil, air, or water with help of organisms • Prokaryotes help clean up oil spills, clean sewage

15. Bacteria and Archaea • Two kinds of prokaryotes: bacteria and archaea • Current theory: Archaea and Eukaryotes have evolved from the same ancestor • Differences: cell wall components (bacteria has peptidoglycan, archaea doesn’t have peptidoglycan); different plasma membrane lipids, etc.

17. Archaea thrive in extreme environments- and in other habitats • Extreme halophiles: salt lovers • Salt-lake • Extreme thermophiles: heat lovers • Hot springs, deep ocean vents (over 100 C) • Methanogens: anaerobic conditions • Mud at bottom of lakes (swamp bubbling) • Almost everywhere else, too!

18. Methanogens Thermophiles

20. Bacteria • Proteobacteria: gram-negative • 5 of the 9 groups • Gram-positive bacteria

21. Bacteria • Cyanobacteria • Plant-like, oxygen producing photosynthesis • Chlamydias

22. Bacteria • Spirochetes: helical (syphilis, Lyme disease)

24. Some bacteria cause disease • Pathogenic bacteria cause about ½ of all human diseases • Most produce poison • Exotoxin: secreted by bacterial cell (Staphlococcus aureus, E. coli O157:H7) • Endotoxin: components of outer membrane of gram- bacteria (Salmonella) • Sanitation has reduced threat, as has education

25. Staph

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27. Bacteria can be used as biological weapons • Millionth of a gram of Bacillus anthracis can kill a person (anthrax) • Gram of aerosolized botulinum toxin can kill 1.5 million people (Clostridium botulinum)

29. The eukaryotic cell probably originated as a community of prokaryotes • Widely accepted view: two processes • Membrane infolding: • Created endomembrane system • Endosymbiosis: • Mitochondria and chloroplasts were at one time free-living prokaryotes (they are very similar to modern day prokaryotes) • Were engulfed by eukaryotic cells (explains extra membranes)

32. Protists are an extremely diverse assortment of eukaryotes • Probably not 1 kingdom • Algae: photosynthesis • Protozoans: heterotrophic • Most are aquatic, unicellular • Have membrane enclosed organelles, cilia and flagella have 9+2 microtubule arrangement

34. Chromalveolates • Autotrophs: • Diatoms: unicellular algae with glassy walls • Dinoflagellates: usually photosynthetic, unicellular, cause red tide • Brown algaes: multicellular, called seaweed, kelp

35. Chromalveolates • Heterotrophs: • Water molds: unicellular, decomposers • Ciliates: move, feed using cilia

36. Rhizarians • Amoebas: • Use pseudopods for movement, feeding • Some have internal or external structures that are rigid or semi-rigid

37. Excavata • Have an excavated feeding groove • Many lack functional ETC in mitochondria, so use anaerobic pathways • Many are human pathogens, parasites

38. Unikonts • More amoebas (free-living, test free) • Slime molds • Plasmodial: huge, but unicellular; bright colors • Cellular: start as amoeboid cells, form glob that produces spores

41. Archaeplastids • Most are autotrophic, colored algaes • Red algae: some have hard outer parts, others commercially important • Green algae: unicellular to multicellular, very similar to plants (NOT plants)

43. Multicellularity evolved several times in eukaryotes • Unicellular organisms: all of life’s activities occur within a single cell • Multicellular organisms: specialized cells for specialized processes • Process: • Ancestral colony formed • Cells in colony become specialized • Specialization continues until formation of sex cells