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From the molecules of life, to the simpler organisms

From the molecules of life, to the simpler organisms. Part I. Paula B. Matheus Carnevali. Outline. The first organisms Classification systems The major divisions of life Phylogeny of bacteria Prokaryotic cell structure and function Gram negative vs. Gram positive.

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From the molecules of life, to the simpler organisms

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  1. From the molecules of life, to the simpler organisms Part I Paula B. Matheus Carnevali

  2. Outline • The first organisms • Classification systems • The major divisions of life • Phylogeny of bacteria • Prokaryotic cell structure and function • Gram negative vs. Gram positive

  3. Cartoon of the tree of life Figure 1. Last Universal Common Ancestor

  4. The first cellular life whose descendants ultimately survived, appeared at least 2 billion years ago and probably much earlier Figure 2. Fossilized bacteria. a) Archean Apex, 3.5 billion yrs old, b) Gloeodiniopsis, 1.5 billion yrs old, c) Palaeolyngbya, 950 million yrs old. From Prescott et al., 2005

  5. Which of its two most vital substances did life acquire first, proteins or DNA?Ribozymes Figure 3. The mechanism of action of the ribozymes. From Essential cell biology, 2/e, 2004, Garland Science

  6. Characteristics of the first organisms • Self-replicating systems • Use of DNA to store heritable information • Use of proteins to express information • Cellular forms • Cellular membranes

  7. Classification of organisms • Taxonomyis the science of biological classification. • Classificationis the arrangement of organisms into groups or taxa (s. taxon) based on mutual similarity or evolutionary relatedness. • Nomenclatureis the branch of taxonomy concerned with the assignment of names to taxonomic groups in agreement with published rules. • Identificationis the process of determining that a particular isolate belongs to a recognized taxon. • Systematicsis the scientific study of organisms with the ultimate object of characterizing and arranging them in an orderly manner.

  8. Some remarkable discoveries in microbiology • Aristotle first classified living things in Plants and Animals • Bacteria were first observed by Anton van Leeuwenhoek in 1676 using a single-lens microscope of his own design. • The invention of the Electron Microscope allowed for the distinction between Prokaryotic and Eukaryotic cells • In the 1960s Robert Whittaker presented the five kingdoms system of classification including Fungi • Based on 16S rDNA Carl Woese and his collaborators suggested that prokaryotes were divided into two distinct groups very early on, and presented the Three domain system including Archaea

  9. Prokaryotes vs. Eukaryotes Table 1. Comparison of Prokaryotic and Eukaryotic cells From Prescott et al., 2005

  10. Prokaryotes vs. Eukaryotes Figure 4. Comparison of Prokaryotic and Eukaryotic cell structure. (a) The prokaryote Bacillus megaterium, (b) The eukaryotic alga Chlamydomonas reinhardtii, a deflagellated cell.From Prescott et al., 2005

  11. Whittaker’s 5-Kingdom system It lacks distinction between Archaea and bacteria. The kingdom Protista also may be too diverse to be taxonomically useful. The boundaries between kingdoms are ill-defined Figure 5. The five kingdom system proposed by Whittaker. From Prescott et al., 2005

  12. Major characteristics used in taxonomy • Classical Characteristics: • Morphological characteristics • Physiological and metabolic characteristics • Ecological characteristics • Genetic analysis • Molecular characteristics: • Comparison of proteins • Nucleic acid base composition • Nucleic acid hybridization • Nucleic acid sequencing

  13. Phylogeny of bacteria Figure 6 . Hierarchical arrangement in taxonomy. From Prescott et al. , 2005 • A prokaryotic species is a collection of strains that share many stable properties and differ significantly from other groups or strains. • A species (genomospecies) is a collection of strains that have a similar G+C composition and 70% or greater similarity as judged by DNA hybridization experiments.

  14. Woese’s three domain system Figure 7. Tree of life by the three domain system

  15. Bacteria, Archaea and Eucarya Table 2. Comparison of Bacteria, Archaea, and Eucarya From Prescott et al., 2005 Figure 8a. Prokaryotic cell Figure 8b. Eukaryotic cell

  16. Table 2 cont. Comparison of Bacteria, Archaea, and Eucarya

  17. Eukaryotic cells arouse form prokaryotic cells Figure 9. A schematic representation of the process of endosymbiosis

  18. Endosymbiotic hypothesis Figure 10. A schematic representation of the process of endosymbiosis

  19. Phylogeny of bacteria Figure 11. Phylogeny of Bacteria. The tree is based on 16S rRNA comparisons. From Prescott et al., 2005.

  20. Purpose of the Gram Stain To separate bacteria based upon their cell wall structure and to determine their morphology and possible cellular arrangement Gram-negative rod Gram-positive cocci in chains Figure 12. The Gram-Positive and Gram-Negative envelopes.From Prescott et al., 2005

  21. Gram negative vs Gram positive Table 3. Comparison between Gram-positive and Gram-negative bacteria Modified from Prescott et al., 2005

  22. Prokaryotic cell organization Figure 13. A prokaryotic cell

  23. Size, shape and arrangement Figure 14. Examples of bacterial shapes. From Prescott et al., 2005

  24. Size, shape and arrangement Figure 15. Comparison between the size of a human cell, bacteria and viruses. From Prescott et al., 2005

  25. Table 4. Prokaryotic structures From Prescott et al., 2005

  26. Plasma membrane Figure 16 . Plasma membrane structure.From Prescott et al., 2005

  27. Cell wall Figure 17. The cell wall. The Gram+ envelope is from Bacillus licheniformis, and the Gram- micrograph is of Aquaspirillum serpens. M=peptidoglycan or murein layer, OM=outer membrane, PM=plasma membrane, P=periplasmic space, W=Gram+ peptidoglycan wall. From Prescott et al., 2005

  28. Gram positive cell walls Figure 18. The Gram-Positive envelope. From Prescott et al., 2005

  29. Gram negative cell walls Figure 19. The Gram-Negative envelope.From Prescott et al., 2005

  30. Bacterial nucleoid Figure 20. Some bacterial nucleoids. From Prescott et al., 2005 E. coli chromosome growing

  31. Flagella and motility Figure 21. The ultrastructure of bacterial flagella. Flagellar basal bodies and hooks in (a) gram-negative and (b) gram-positive bacteria. From Prescott et al., 2005

  32. Flagella and motility Figure 22. The long flagella and the numerous shorter fimbriae on Proteous vulgaris. (a) Monotrichous polar, (b) Lophotricous, (c) Peritrichous. From Prescott et al., 2005

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