1. Chapter 4 Prokaryotic organisms

2. Prokaryotic cell Includes bacteria and archaea Thousands of species of bacteria differ by morphology (shape), chemical composition, nutritional requirements, biochemical activities, and sources of energy Bacteria divide by binary fission (asexual reproduction)

3. Size, shape, and arrangement Most bacteria range in size between 0.2 micrometers (microns) to 2.0 microns The basic shapes are cocci, bacilli, and spirilla Cocci may occur in pairs (diplococci), in chains (streptococci), and in clusters (staphylococci) Bacilli may appear as single rods, diplobacilli, streptobacilli, or coccobacilli

4. Other shapes Spiral bacteria have one or more twists Curved rods (comma shaped) are vibrios Others called spirilla are corkscrew shaped and move with whip-like appendages called flagella Spirochetes are helical and flexible and move by axial filaments Most bacteria maintain a single shape and are monomorphic, but some may have more than one shape and are pleomorphic

5. Structures external to cell wall Glycocalyx means sugar coat, and is a sticky, gelatinous polymer that is outside the cell wall If the glycocalyx is firmly attached to cell wall and is organized it is called a capsule If the glycocalyx is unorganized and loosely attached it is called a slime layer Streptococcus pneumoniae, Haemophilus influenzae, Bacillus anthracis have them

6. Flagella These are long, filamentous appendages that help bacteria move (motile) No flagella is called atrichous A single polar flagellum is monotrichous A tuft of flagella at each end is amphitrichous Two or more at one (or both) ends is lophotrichous Flagella all over is peritrichous

8. Flagella The flagellum has 3 basic parts: filament is the long, outermost region; a hook attaches to the filament; the basal body, which anchors the flagellum to the cell wall and plasma membrane The basal body is a small central rod inserted into a series of rings In gram negative bacteria, there are two pair of rings In gram positive bacteria, only the inner pair is present

9. Motility Bacteria have a ‘run and tumble’ movement thanks to flagella A bacterium with flagella can move quickly toward or away from a stimulus Bacteria moving toward chemical stimulus is positive chemotaxis Bacteria moving away is negative chemotaxis Moving in response to light is phototaxis

10. Axial Filaments Spirochetes are unique in structure and motility Treponema pallidium causes syphilis, Borrelia burgdorferi causes Lyme disease Spirochetes move by axial filaments, which spiral around the cell and cause a corkscrew like movement

11. Fimbriae and Pili Many gram negative bacteria contain shorter hairlike appendages called fimbriae and pili These are used for attachment and transfer of DNA Fimbriae help cell stick to surfaces (Neisseria gonorrhoeae) Pili (sex pili or conjugation pili) help cells transfer DNA in conjugation

12. Cell Wall Helps maintain shape of the cell Keeps cell from rupturing Contributes to ability to cause disease Is the site of action of some antibiotics Helps tell differences in major types of bacteria

13. Composition Contains peptidoglycan which consists of repeating disaccharides attached by polypeptides that forms a lattice Disaccharide portion has monosaccharides called N-acetyl glucosamine (NAG) and N- acetylmuramic acid (NAM) Alternating NAG and NAM are linked to form a backbone, and adjacent rows are linked by polypeptides

14. Difference between gram positive and negative cells Gram negative have an outer membrane Gram positive cells do not have an outer membrane, so the peptidoglycan is exposed and more easily destroyed by antibiotics like penicillin

15. Gram negative vs. Gram positive Gram positive cell wall has thick peptidoglycan Gram negative has a thin layer Gram positive cell has teichoic acids which help bind and regulate movement of cations in/out of the cells Teichoic acids may also provide antigenic specificity which makes it easier to ID bacteria

16. Gram negative cells Have thin layer of peptidoglycan and an outer membrane The outer membrane (OM) has lipopolysaccharide (LPS), lipoprotein, and phospholipid It has a negative charge which helps the bacteria avoid phagocytosis and complement (both are host defenses)

17. Gram negative OM It also is a barrier to antibiotics, enzymes, etc. Has porins (proteins) which allow passage of some material in and out LPS component has an O polysaccharide portion and a lipid portion (lipid A) The O polysaccharide is an antigen and is used to help ID the bacteria The Lipid A is a toxin (endotoxin) that can cause fever and shock (endotoxin shock)

18. Atypical cells Mycoplasma has no cell wall (causes walking pneumonia), but do have sterols to protect against rupture Acid Fast Cell Walls- Mycobacterium and Nocardia have mycolic acid in cell wall, which causes these bacteria to clump and stick together. Damage to cell wall by lysozyme causes either a spheroplast (gram negative) or a protoplast (gram positive)

19. Cell or Plasma Membrane Encloses the cytoplasm Made of phospholipids (bilayer), proteins, glycoprotein, glycolipid Arrangement is phospholipid bilayer Heads (hydrophilic), tails (hydrophobic) Selective permeability ATP production occurs here

20. Movement across membranes Passive process-movement from high concentration to low without using ATP Includes simple diffusion (alka seltzer example) Facilitated diffusion-requires a protein transporter to allow movement across membrane Osmosis-movement of water from greater water to less water

21. Osmosis Movement produces osmotic pressure-this is the pressure needed to stop the flow of water across the membrane 3 types of osmotic solutions: isotonic-equal solid; no change in cell when placed in this type of solution Hypotonic=less solid, cell will swell Hypertonic=greater solid; cell will shrink

22. Inside cell Cytoplasm is 80% water and contains proteins, carbohydrates, lipids, inorganic ions, and contains the nuclear area, ribosomes, and inclusions Nuclear area contains loop shaped DNA May have pieces of DNA called plasmids that carry genes for resistance (resistance factors or R factors)

23. Inside cell continued Ribosomes-sites of protein synthesis Contained in eukaryotic cells too, but different because they are 80 S (Svedberg unit); 40 S + 60 S) Prokaryotic ribosomes are 70 S (30 S + 50 S) Inclusions are extra storage areas including gas vacuoles, sulfur granules, land lipid inclusions Metachromatic granules -collectively known as volutin, represents a reserve of inorganic phosphate Magnetosomes-inclusions of iron oxide found in some gram negatives that act like magnets

24. Endospores Form in gram positive rods when essential nutrients are depleted Endospores are highly durable and can survive extremes of heat, dehydration, and exposure to toxins and radiation Begin sporulation when a key nutrient becomes scarce Endospores may remain dormant for years, and will eventually ‘germinate’ and become a vegetative cell again

25. Shapes, review Shapes; cocci (spherical), bacilli (rods), vibrio (comma), spirochetes (spring), spirillum (helix) Arrangements: Staphylo (clusters), strepto (chains), mono (single), diplo (pairs), tetrads (4), sarcina (8), palisade (side by side like a picket fence) Pleomorphism-variable shapes like Corynebacterium