BIO 411

1. BIO 411 Chapter 3 – Bacterial Morphology and Cell Wall Structure and Synthesis

2. Prokaryote vs. Eukaryote • Get with a partner and make a list of the differences between Prokaryotes and Eukaryotes. • List differences on board • Amazing cell size demo!

3. Shapes of Bacteria • Almost all bacteria have one of three morphologies (or shapes): • coccus - spherical-shaped (pl., cocci) • Diplococcus • Streptococcus • Staphylococcus • bacillus - rod-shaped (pl., bacilli) • spirillum - spiral-shaped (pl., spirilla) • Figure 3-3 B

4. Gram Stain • Gram Stain • Crystal violet • Iodine • Decolorizer (EtOH or Acetone) • Safranin • Gram + vs. Gram – cells • “P” – purple, positive • Figure 3-3 A • Only dependable on new cultures (24hr)

5. Bacterial Cell Structure • Typical prokaryotic cell - Figure 3.1 • Inside-Out Approach • What is the cytoplasm? • ~80% water

6. Cytoplasm • Also contains: • The bacterial chromosome (structure?) • It is about 1mm long (1000X longer than the cell) • It’s localized in the nucleoid • Plasmids – small circular pieces of non-chromosomal DNA • Functions? • Ribosomes (70S) – function? • Protein synthesis

7. Cytoplasm • Cytoplasmic membrane – typical lipid bilayer • Carries out many functions associated with eukaryotic organelles • Mesosome – anchor to separate daughter chromosomes during cell division • Figure 3-1

8. Bacterial Cell Structure (cont.) • Next layer: Bacterial Cell Wall • Composed of sub-units found nowhere else in nature • site of action of some of the most effective antibiotics • cell wall determines a cell’s morphology • Primary Function – protect cell from exploding (osmotic pressure)!!!

9. Bacterial Cell Structure (cont.) • Cell Wall Structure • Bacterial cell walls are composed of peptidoglycan • the glycan portion of peptidoglycan is made of a huge polymer of carbohydrates containing: • N-acetylmuramic acid (NAM) and • N-acetylglucosamine (NAG) • These long chains of alternating NAM and NAG are held together by short peptide cross-bridges • log raft analogy

10. Gram+ vs. Gram- Cell Walls • Gram+ cells have a very thick, multilayered cell wall • they also contain teichoic acids and lipoteichoic acids • Lysozyme • Figure 3-2 A • Gram- cells have a very thin layer of peptidoglycan • they also have an outer membrane in addition to the cytoplasmic membrane • the space between these two membranes is called the periplasmic space or periplasm

11. Gram+ vs. Gram- Cell Walls (cont.) • the outer membrane is an asymmetric bilayer: • Phospholipids on the inside • lipopolysaccharides (LPS) on the outside • LPS structure: • Lipid A - also called endotoxin because it damages cells and tissues (also causes fever and shock) • Core Polysaccharide • O antigen – distinguishes serotypes of a species (E. coliO157:H7) • Figure 3-10

12. Gram+ vs. Gram- Cell Walls (cont.) • Porins allow non-specific transport across the membrane • Figure 3-2 B • Basis for the Gram stain reaction (Figures 3-2 and 3-3 A)

13. Bacterial Cell Structures • Capsule outer coating of sticky polysaccharide or protein • Also called a glycocalyx or slime layer • Functions? • Antiphagocytic and poorly antigenic - Streptococcus pneumoniae • Adherence - Streptococcus mutans and dental caries, many other examples too! • Biofilm - protection

14. Movement of Prokaryotic Cells • Flagella - ropelike propeller composed of flagellin • Chemotaxis • bacteria can move toward nutrients or away from toxic substances • Mechanism – “swim and tumble”

15. Attachment of Prokaryotic Cells • Bacteria can use fimbriae and pili to attach to surfaces and other cells • fimbriae are numerous, short protein filaments of attachment (E. coli and Neisseria gonorrhoeae) • pili are long protein filaments for attachment of bacteria to other bacterial cells • Used for DNA transfer • Figure 3-4

16. Mycobacteria and Mycoplasmas • Mycobacteria have a peptidoglycan cell wall, but they contain an outer covering of mycolic acid • Antiphagocytic • Acid-fast stain • Mycoplasmas do not have a cell wall

17. Bacterial Endospores • Some types of Gram+ bacteria have the ability to form endospores • Primary genera Bacillus and Clostridium • the endospore is the “navy seal” of living organisms • Vegetative State vs. Endospore • Endospore production – Figure 3-12

18. Bacterial Endospores (cont.) • Endospore germination • Important Point: • endospores are not a means of reproduction • Importance of endospores

19. Disease of the Day • Anthrax • Etiology – Bacillus anthracis (via toxins) • Aerobic, endospore-forming, • Reservoir – Contaminated animals (herbivores) and animal products • Transmission and Development • Cutaneous anthrax – through a cut in the skin • Figure 25-3, page 268 • 20% mortality w/o treatment, less than 1% with • Gastrointestinal anthrax – rare (~100% mortality)

20. Disease of the Day • Inhalational or Pulmonary anthrax – endospores inhaled • Can show 2 or more months of latency • Days 1-2 mild fever, cough, chest pain (non-specific) • Death usually occurs within 3 days w/o treatment • Almost 100% mortality • Lab ID: microscopy and specific antigen detection • Prevention and Control • vaccine (6 initial + yearly booster) • antibiotics effective if given in time

21. Cell Structure Review • Find a partner and review the structure of bacterial cells

22. Endosymbiosis • The Theory of Endosymbiosis • Supporting Evidence: • Mitochondrial DNA • 70S ribosomes • Binary Fission • RNA sequencing