BACTERIAL MORPHOLOGY: PROCARYOTIC AND EUCARYOTIC CELLS Chapter 4

1. BACTERIAL MORPHOLOGY:PROCARYOTIC AND EUCARYOTIC CELLSChapter 4

2. Eucaryotic cells • any organism with a fundamental cell type containing membrane-enclosed organelles

3. Prokaryotic Cells • Comparing Prokaryotic and Eukaryotic Cells • Prokaryote comes from the Greek words for prenucleus. • Eukaryote comes from the Greek words for true nucleus.

4. Prokaryote Eukaryote • Paired chromosomes, in nuclear membrane • Histones • Organelles • Polysaccharide cell walls • Mitotic spindle • One circular chromosome, not in a membrane • No histones • No organelles • Peptidoglycan cell walls • Binary fission

5. Procaryotes (Bacteria) • Average size: 0.2 -1.0 µm  2 - 8 µm • Basic shapes:

6. Protozoan (eucaryote)

7. Procaryotic cells • any organism with a fundamental cell type without nucleus

8. Unusual shapes • Star-shaped Stella • Square Haloarcula • Most bacteria are monomorphic • A few are pleomorphic Figure 4.5

9. Bacteria (procaryote)

10. Procaryotic cells (cont.) • Bacteria • Differentiation by: • Morphology, composition, nutritional requirements, and biochemical activities and source of energy

11. Shapes of bacteria • coccus (spheres) • bacillus (rods) • spiral (twisted) • pleomorphic (several)

19. Arrangements • Pairs: diplococci, diplobacilli • Clusters: staphylococci • Chains: streptococci, streptobacilli

20. Arrangements of cocci • Divide in: • one plane=diplococci • two planes=tetrads • three planes=sarcineae • multiple=staphylococci

27. Structures external to the bacterial cell wall • Glycocalyx • Flagella • Axial filaments • Fimbriae and pili

29. Glycocalyx • Capsule (firm) or slime layer (loose) • polysaccharide and/or polypeptide • Inhibits phagocytosis • Attaches to host surfaces • Protects against desiccation

30. Glycocalyx • Outside cell wall • Usually sticky • A capsule is neatly organized • A slime layer is unorganized & loose • Extracellular polysaccharide allows cell to attach • Capsules prevent phagocytosis Figure 4.6a, b

31. Bacterial glycocalyx

32. Streptococcus pneumoniae capsule

33. Flagella • Outside cell wall • Made of chains of flagellin • Attached to a protein hook • Anchored to the wall and membrane by the basal body • They propel bacteria around

34. Flagella

36. Motile Cells • Rotate flagella to run or tumble • Move toward or away from stimuli (taxis) • Flagella proteins are H antigens (e.g., E. coli O157:H7)

37. Lophotrichous Monotrichous Peritrichous

38. Types of Flagella

39. Types of Flagella Main function: to propel bacteria to and from area’s of nutrients/toxic environments

40. Types of Flagella

41. Axial filaments • Present in spiral cells • Similar to flagella, but they wrap around the cell • Corkscrew motion enables a bacterium such as T.pallidum (causative agent of Syphilis) to move effectively through body fluids (vaginal secretions)

43. Fimbriae, pili and sex pili • Short thin appendages • Fimbriae and pili • Help cells to adhere to surfaces • Sex pili • Bridge between bacterial cells for DNA transfer

44. DNA transfer through a sex pili

45. Fimbriae

46. Fimbriae allow attachment to teeth, stones in creeks, plastic catheter's in hospitals • Pili are used to transfer DNA from one cell to another Fimbriae

47. Intestinal mucosa E. coli

48. Cell wall • Surrounds the plasma membrane • Protects the cell from osmotic pressure changes • Lattice formed by peptidoglycan (murein)

49. Cell Wall • Prevents osmotic lysis • Made of peptidoglycan (in bacteria) Figure 4.6a, b

50. Peptidoglycan (murein) • N-acetylglucosamine (NAG) • N-acetylmuramic acid (NAM) • repeating disaccharides joined by polypeptides