Functional Anatomy of Prokaryotic Chapter 4 Functional Anatomy of Prokaryotic

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

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

Unusual shapes Star-shaped Stella Square Haloarcula Figure 4.5

Sterptococcus pneumoniae Diplococci Gram positive Cause pneumonia disease

Staphylococcus aureus Gram positive Normal microbiota on skin aureus = golden colony

Streptococcus pyogenes Gram positive bacteria Cocci Cause strep throat , Tonsillitis and Impetigo

Bacillus anthracis Gram positive Spore forming Bacilli Cause Anthrax disease

Salmonella typhi Gram negative Bacilli Flagellated Cause typhoid fever

Clostridium botulinum Gram positive Bacilli Spore forming Cause Food borne botulism

Vibrio cholerae Gram negative Comma shaped Flagellated Cause cholera disease

Helicobacter pylori Gram negative Helix shaped Cause gastric ulcer

Treponema pallidum Helically coiled microorganism Cause syphilis disease

Most bacteria are monomorphic A few are pleomorphic

The shape of a bacterium is determined by heredity. Genetically, most bacteria are monomorphic that is, they maintain a single shape. However, a number of environmental conditions can alter that shape.

If the shape is altered, identification becomes difficult. Some bacteria, such as Rhizobium and Corynebacterium are genetically pleomorphic, which means they can have many shapes, not just one.

Arrangements Pairs: diplococci, diplobacilli Clusters: staphylococci Chains: streptococci, streptobacilli

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

Flagella Outside cell wall Made of chains of flagellin Attached to a protein hook Anchored to the cell wall and cell membrane by the basal body Figure 4.8

Flagella Arrangement Figure 4.7

Figure 4.8

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)

Motile Cells Figure 4.9

Axial Filaments Endoflagella In spirochetes Anchored at one end of a cell Rotation causes cell to move Figure 4.10a

Fimbriae and Pili Fimbriae allow attachment Pili are used to transfer DNA from one cell to another

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

Peptidoglycan Polymer of disaccharide N-acetylglucosamine (NAG) & N-acetylmuramic acid (NAM) Linked by polypeptides Figure 4.13a

Figure 4.13b, c

Gram-positive cell walls Gram-negative cell walls Thick peptidoglycan Teichoic acids In acid-fast cells, contains mycolic acid Thin peptidoglycan No teichoic acids Outer membrane

Gram-Positive cell walls Teichoic acids: Lipoteichoic acid links to plasma membrane Wall teichoic acid links to peptidoglycan May regulate movement of cations Polysaccharides provide antigenic variation Figure 4.13b

Gram-Negative Outer Membrane Lipopolysaccharides, lipoproteins, phospholipids. Forms the periplasm between the outer membrane and the plasma membrane. Protection from phagocytes, complement, antibiotics. O polysaccharide antigen, e.g., E. coli O157:H7. Lipid A is an endotoxin. Porins (proteins) form channels through membrane

Gram-Negative Outer Membrane Figure 4.13c

Gram Stain Mechanism Crystal violet-iodine crystals form in cell Gram-positive Alcohol dehydrates peptidoglycan CV-I crystals do not leave Gram-negative Alcohol dissolves outer membrane and leaves holes in peptidoglycan CV-I washes out

Atypical Cell Walls Mycoplasmas Lack cell walls Sterols in plasma membrane Archaea Wall-less, or Walls of pseudomurein (lack NAM and D amino acids)

Damage to Cell Walls Lysozyme digests disaccharide in peptidoglycan. Penicillin inhibits peptide bridges in peptidoglycan. Protoplast is a wall-less cell( completely or partially removed). Spheroplast is a cell from which the cell wall has been almost completely removed.

Damage to Cell Walls L forms or cell wall deficient bacteria (CWD) are wall-less cells that swell into irregular shapes such as Mycoplasma . Protoplasts and spheroplasts are susceptible to osmotic lysis.

Plasma Membrane Figure 4.14a

Plasma Membrane Phospholipid bilayer Peripheral proteins Integral proteins Transmembrane proteins Figure 4.14b

Fluid Mosaic Model Membrane is as viscous as olive oil. Proteins move to function Phospholipids rotate and move laterally Figure 4.14b

Plasma Membrane Selective permeability allows passage of some molecules Enzymes for ATP production Photosynthetic pigments on foldings called chromatophores or thylakoids

Plasma Membrane Damage to the membrane by alcohols, quaternary ammonium (detergents) and polymyxin antibiotics causes leakage of cell contents.

Movement Across Membranes Simple diffusion: Movement of a solute from an area of high concentration to an area of low concentration. Facilitative diffusion: Solute combines with a transporter protein in the membrane.

Movement Across Membranes Figure 4.17

Movement Across Membranes Osmosis Movement of water across a selectively permeable membrane from an area of high water concentration to an area of lower water. Osmotic pressure The pressure needed to stop the movement of water across the membrane. Figure 4.18a

Figure 4.18c-e

Movement Across Membranes Active transport of substances requires a transporter protein and ATP. Group translocation of substances requires a transporter protein and PEP.

Cytoplasm Cytoplasm is the substance inside the plasma membrane Figure 4.6a, b

Nuclear Area Nuclear area (nucleoid) One circular chromosome Figure 4.6a, b

Ribosomes Figure 4.6a

Ribosomes Figure 4.19

Ribosomes Ribosomes are the sites of protein synthesis in bacteria. Several antibiotics such as streptomycin, neomycin, tetracyclines, and chloramphenicol specifically inhibit protein synthesis by attacking ribosomes.

Cytoplasmic inclusions 1- Metachromatic granules 2- Polysaccharide granules 3- Lipid inclusions 4- Sulfur granules 5- Carboxysome 6- Gas vacules 7- Magnetosomes

1- Metachromatic granules Metachromatic granules = polyphosphate granules= volutin granules Large granule Volutin granules + methylene blue  red color Volutin reserve of inorganic phosphate( ATP , DNA, Phospholipid ) Present in algae, fungi, protozoa and bacteria. Diagnostic significance of Corynebacterium diphtheria

Metachromatic granules

Metachromatic granules

2- Polysaccharide granules Consist of glycogen and starch Can be demonstrated by iodine when applied to the cells. Glycogen + iodine  redish brown color Starch + iodine  blue color Energy reserves

Polysaccharide granules

3- Lipid inclusions Appear in various species Mycobacterium and Bacillus. Energy reserves Polymer of Poly beta hydroxy butyric acid Polymer of Poly beta hydroxy butyric acid + sudan black stain  red color

Lipid inclusions

4- Sulfur granules Sulfur bacteria that belong to the genus Thiobacillus Derive energy by oxidizing sulfur and sulfur containing compounds. These bacteria may deposit sulfur granules in the cell, where they serve as an energy reserve.

Sulfur granules

5- Carboxysome Are inclusions that contain the enzyme Ribulose 1,5-diphosphate carboxylase for CO2 fixation Bacteria that use carbon dioxide as their sole source of carbon require this enzyme for carbon dioxide fixation during photosynthesis. Example: cyanobacteria.

6- Gas vacules Hallow cavities found in many aquatic prokaryotes Maintain buoyancy, so that the cells can remain at the depth in the water appropriate for them to receive sufficient amounts of oxygen, light, and nutrients.

7- Magnetosomes Inclusions of iron oxide Fe3O4 Formed by several gram negative bacteria such as Aquaspirillum magnetotacticum that act like magnets Orient magnetotactic bacteria in geomagnetic fields Destroys H2O2

Magnetosomes

Endospores Resting cells Resistant to desiccation, heat, chemicals Bacillus, Clostridium Sporulation: Endospore formation Germination: Return to vegetative state

Endospores