Exam 1 Review PDF

Exam 1 review Andrei Kouranov 1. Bacterial cell wall structure: Gram + & Gram –; “Acid fast” 2. Bacterial cellular morphology & cellular arrangement 3. Components of prokaryotic cell: internal & external 4. Components of eukaryotic cell: internal & external 5. Bacterial chemotaxis 6. Endosp...

Exam 1 review Andrei Kouranov 1. Bacterial cell wall structure: Gram + & Gram –; “Acid fast” 2. Bacterial cellular morphology & cellular arrangement 3. Components of prokaryotic cell: internal & external 4. Components of eukaryotic cell: internal & external 5. Bacterial chemotaxis 6. Endospores 7. Fungi & protozoa 8. Taxonomy: Domains & Kingdoms of life Figure 3.2 Typical Prokaryotic Cell Bacterial DNA: Represented by only one chromosome Circular Double stranded, helical structure Eukaryotic DNA: Represented by multiple chromosomes Linear (majority cases) Double stranded, helical structure Plasmids small circular, double-stranded DNA free or integrated into the chromosome duplicated and passed on to offspring not essential to bacterial growth & metabolism may encode antibiotic resistance, tolerance to toxic metals, enzymes & toxins used in genetic engineering- readily manipulated & transferred from cell to cell 5 Figure 3.3 Typical Eukaryotic Cell Figure 3.36 Eukaryotic Nucleus Nucleus contains a suborganelle – nucleolus. Nucleolus is an organelle where RNA components of ribosome are synthesized Cytoplasm of Eukaryotes (6 of 14) Membranous Organelles Nucleus Often largest organelle in cell Contains most of the cell’s DNA Semiliquid portion called nucleoplasm Contains chromatin RNA synthesized in nucleoli present in nucleoplasm. Surrounded by nuclear envelope Contains nuclear pores Figure 3.41 Mitochondrion  Bacterial Cell Walls Gram positive Gram negative Acid-fast No cell wall (Mycoplasmas) Bacterial Cell Walls (3 of 4) Gram-Positive Bacterial Cell Walls Relatively thick layer of peptidoglycan Contain unique chemicals called teichoic acids and lipoteichoic acids Appear purple following Gram staining procedure Up to 60% mycolic acid in acid-fast bacteria helps cells survive desiccation Figure 3.16a Comparison of Cell Walls of Gram-Positive and Gram- Negative Bacteria Bacterial Cell Walls (1 of 2) Gram-Negative Bacterial Cell Walls Have only a thin layer of peptidoglycan Bilayer membrane outside the peptidoglycan contains phospholipids, proteins, and lipopolysaccharide (LPS) Lipid A portion of LPS can cause fever, vasodilation, inflammation, shock, and blood clotting. May impede the treatment of disease. Appear pink following Gram staining procedure Figure 3.16b Comparison of Cell Walls of Gram-Positive and Gram- Negative Bacteria Gram-negative bacteria contain the outer membrane enriched with lipopolysaccharides There is a large periplasmic space between inner and outer membrane in gram-negative bacteria. Many types of bacteria and archaea contain S-layer outside of cell-wall or outer membrane “The S-layers of both archaea and bacteria consists of a monomolecular layer composed of only one (or, in a few cases, two) identical proteins or glycoproteins.” Wikipedia Differential Gram staining Step Microscopic Appearance of Cell Chemical Reaction in Cell Wall (very magnified view) Gram (+) Gram (–) Gram (+) Gram (–) 1. Crystal violet First, crystal violet is added to the cells in a smear. It stains them all the same purple color. Both cell walls affix the dye 2. Gram’s iodine Then, the mordant, Gram’s iodine, is added. This is a stabilizer that causes the dye to form large complexes in the peptidoglycan meshwork of the cell wall. The thicker gram-positive cell walls are able to more firmly trap the large complexes than those of the gram-negative cells. Dye complex No effect trapped in wall of iodine 3. Alcohol Application of alcohol dissolves lipids in the outer membrane and removes the dye from the peptidoglycan layer—only in the gram-negative cells. Crystals remain Outer membrane in cell wall weakened; wall loses dye 4. Safranin (red dye) Because gram-negative bacteria are colorless after decolorization, their presence is demonstrated by applying the counterstain safranin in the final step. Red dye masked Red dye stains by violet the colorless cell  Bacterial shapes and arrangements Pleomorphism: variation in the size and shape of cells of a single species due to nutritional and genetic differences Figure 3.13 Bacterial Shapes and Arrangements (c) Bacterial Arrangements  Bacterial Shapes and Arrangements (cont’d) Arrangement of cocci: Arrangement of bacilli: Single – Single Diplococci: pairs – Diplobacilli: pair of cells with ends attached Tetrads: groups of four – Streptobacilli: chain of Staphylococci or several cells micrococci: irregular – Palisades: cells of a chain clusters remain partially attached by Streptococci: chains a small hinge region at the ends Spirilla: occasionally found in short chains Spirochetes: rarely remain attached after cell division  Bacteria can move rotating flagellum( flagella) (a) (b) (c) (d) a. monotrichous – single flagellum at one end b. lophotrichous – small bunches arising from one end of cell Endoflagellum in spirochete c. amphitrichous – flagella at both ends of cell confined within the d. peritrichous – flagella dispersed over surface of cell, slowest periplasm, between the inner and outer cell membrane Fimbrae fine hairlike bristles from the cell surface function in adhesion to other cells and surfaces, involved in formation of biofilms 22 Figure 3.12 Pili Bacterial mating: conjugation 24 Gycocalyx – key component of bacterial slime layer or capsule Coating of molecules external to the cell wall, made of sugars and/ or proteins 2 types 1. capsule - highly organized, tightly attached 2. slime layer - loosely organized and attached functions attachment inhibits killing by white blood cells receptor 25  Two types of glycocalyx Slime layer glycocalyx helps Streptococcus mutans to attach to smooth surface of teeth and cause teeth decay 26  Chemotaxis: move in response of chemical signal (Clockwise rotation) (Counterclockwise rotation = smooth linear direction) Taxonomy - science for organizing, classifying & naming living things Taxonomic categories from top to the bottom: Domain - Archaea, Bacteria & Eukarya- Three domains of life Kingdom Phylum or Division Class Order Family Genus species 28 Examples of Taxonomy: Organized into several descending ranks, beginning with the most general and ending with the smallest and most specific Figure 3.25b Endospores  Endospores Resting, dormant cells produced by some G+ genera: Clostridium, Bacillus (mainly bacilli type bacteria) Have a 2-phase life cycle – vegetative cell & an endospore sporulation -formation of endospores germination- return to vegetative growth hardiest of all life forms withstand extremes in heat, drying, freezing, radiation & chemicals not a means of reproduction 31 Example of endospore forming bacteria Endospore Example of endospore forming pathogens: Clostridium tetani (Tetunus) Clostridium perfringes (Gas gangrene) Clostridium botulinum (Botulism) Clostridium difficale (C.diff) Bacillus anthracis (Anthrax) Cellular components that help protozoan (Kingdom Protista) to move: pseudopodia; flagellum, cilia Amoeba Euglena Pseudopodia Vacuole Nucleus Storage vesicles Paramecium Saprophytic – live on dead, decomposing matter Forms of fungi: Molds form intertwining filaments called hyphae that forms mycelium Yeasts are unicellular, propagate by budding or fission, may form chains called pseudohyphae