Microbiology - Week 5 - Lecture 1 - Bacterial Cell Biology.pdf

BACTERIAL CELL STRUCTURE M O R P H O L O G Y, E X T E R N A L S T R U C T U R E S , R E P L I C AT I O N S T R AT E G I E S Prepared by: Nick Inglis, Ph.D. BMS 100 Week 5 BASIC MORPHOLOGY OF BACTERIA Coccus Spirillum Coccobacillus Spirochete Bacillus Pleomorphic Vibrio HOW THEY LOOK UNDER A MICROSCO...

BACTERIAL CELL STRUCTURE M O R P H O L O G Y, E X T E R N A L S T R U C T U R E S , R E P L I C AT I O N S T R AT E G I E S Prepared by: Nick Inglis, Ph.D. BMS 100 Week 5 BASIC MORPHOLOGY OF BACTERIA Coccus Spirillum Coccobacillus Spirochete Bacillus Pleomorphic Vibrio HOW THEY LOOK UNDER A MICROSCOPE: 1. COCCI Light microscope, ~1000X EM, ~100,000X HOW THEY LOOK UNDER A MICROSCOPE: 2. BACILLI Light microscope, ~1000X EM, ~100,000X HOW THEY LOOK UNDER A MICROSCOPE: 3. COCCOBACILLUS Light microscope, ~1000X EM, ~100,000X HOW THEY LOOK UNDER A MICROSCOPE: 4. VIBRIOS Light microscope, ~1000X EM, ~100,000X HOW THEY LOOK UNDER A MICROSCOPE: 5. SPIRILLA Light microscope, ~1000X EM, ~100,000X HOW THEY LOOK UNDER A MICROSCOPE: 6. SPIROCHAETES Light microscope, ~1000X EM, ~100,000X BINARY FISSION IN BACTERIA 1 Chromosome replication begins. Origin of replication E. coli cell Two copies of origin Cell wall Plasma membrane Bacterial chromosome BINARY FISSION IN BACTERIA 1 Chromosome replication begins. 2 Replication continues. Origin of replication E. coli cell Cell wall Plasma membrane Bacterial chromosome Two copies of origin Origin Origin BINARY FISSION IN BACTERIA 1 Chromosome replication begins. 2 Replication continues. 3 Replication finishes. Origin of replication E. coli cell Cell wall Plasma membrane Bacterial chromosome Two copies of origin Origin Origin BINARY FISSION IN BACTERIA 1 Chromosome replication begins. 2 Replication continues. 3 Replication finishes. 4 Two daughter cells result. Origin of replication E. coli cell Cell wall Plasma membrane Bacterial chromosome Two copies of origin Origin Origin BACTERIAL REPRODUCTION: 2. SNAPPING DIVISION BACTERIAL REPRODUCTION: 3. SPORES OF ACTINOMYCETES Spores BACTERIAL REPRODUCTION: 4. BUDDING DNA is replicated One daughter DNA molecule is moved into bud Young bud Daughter cell ARRANGEMENT OF BACTERIA: COCCI ARRANGEMENT OF BACTERIA: BACILLI BACTERIAL CELL EXTERNAL STRUCTURES: 1. GLYCOCALYCES Filament Direction of rotation during run BACTERIAL CELL EXTERNAL STRUCTURES: 2. FLAGELLA Rod Peptidoglycan layer (cell wall) Protein rings Cytoplasmic membrane Cytoplasm Flagellin Gram + BACTERIAL CELL EXTERNAL STRUCTURES: 2. FLAGELLA Peritrichous Single polar flagellum Tuft of polar flagella HOW FLAGELLATED BACTERIA Attractant MOVE: A BIASED RANDOM WALK Run Chemotaxis Phototaxis Etc. Tumble Coordinated, Counterclockwise Run Random flagellar rotation Tumble BACTERIAL CELL EXTERNAL STRUCTURES: 3. FIMBRIAE Flagellum Fimbria BACTERIAL CELL EXTERNAL STRUCTURES: 4. PILI Conjugation pilus BACTERIAL CELL EXTERNAL STRUCTURES: 5. BACTERIAL CELL WALL Found on virtually all Bacteria Roles: Protection (many antimicrobial drugs target cell walls) Attachment to other bacteria or cells Resistance to osmotic forces Give shape to the cell THE BASIC COMPONENT OF ANY BACTERIAL CELL WALL Peptidoglycan – polysaccharide comprised of repeating N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM) THE BASIC STRUCTURE OF ANY BACTERIAL CELL WALL Sugar backbone....... Tetrapeptide (amino acid) crossbridge Connecting chain of amino acids TWO BASIC TYPES OF BACTERIAL CELL WALLS: 2. GRAM NEGATIVE CELL WALLS Porin Outer membrane of cell wall Porin (sectioned) Peptidoglycan layer of cell wall Cytoplasmic membrane Gram-negative cell wall n Phospholipid layers Lipopolysaccharide (LPS) O side chain (varies In length and composition) Integral proteins Core polysaccharide Lipid A (embedded in outer membrane) Periplasmic space Fatty acid THE GRAM STAIN Hans Christian Gram (1884) – the most common staining technique in biology; differentiates between gram negative and positive bacteria. THE GRAM STAIN Primary stain – stains everything Slide is flooded with crystal violet for 1 min, then rinsed with water. Result: All cells are stained purple. THE GRAM STAIN Slide is flooded with iodine for 1 min, then rinsed with water. Result: Iodine acts as a mordant; all cells remain purple. THE GRAM STAIN Slide is flooded with solution of ethanol and acetone for 10–30 sec, then rinsed with water. Result: Smear is decolorized; Gram-positive cells remain purple, but Gram-negative cells are now colorless. Decolourizing agent – breaks down thin cell wall of gram negatives, causing stain to be washed away THE GRAM STAIN Slide is flooded with safranin for 1 min, then rinsed with water and blotted dry. Result: Gram-positive cells remain purple, Gram-negative cells are pink. Counterstain – provides contrast to primary stain. GRAM STAIN FAILS TO IDENTIFY MYCOBACTERIUM AND NOCARDIA BACTERIA Gram positive; they have very waxy cell walls that reject crystal violet The Ziehl-Neelsen acid-fast staining technique used instead Acid-fast bacteria – pink/red Non-acid-fast - blue BACTERIAL CYTOSOLIC COMPONENTS: OVERVIEW Liquid contents: cytosol – includes ions, carbs, proteins (enzymes), lipids, waste products Contains nucleoid region BACTERIAL CYTOSOLIC COMPONENTS: 1. INCLUSIONS Polyhydroxybutyrate (PHB) in inclusion bodies SOME BACTERIA CONTAIN ENDOSPORES Cell wall Bacillus, Clostridium Cytoplasmic membrane DNA is replicated. DNA A cortex of calcium and dipicolinic acid is deposited between the membranes. Cortex Vegetative cell Spore coat forms around endospore. DNA aligns along the cell’s long axis. Cytoplasmic membrane invaginates to form forespore. Forespore Endospore matures: completion of spore coat and increase in resistance to heat and chemicals by unknown process. Endospore is released from original cell. Cytoplasmic membrane grows and engulfs forespore within a second membrane. Vegetative cell’s DNA disintegrates. First membrane Second membrane Spore coat Outer spore coat Endospore Outer spore coat THANK YOU! A N D H AV E A L O V E LY D AY !