Copyright © 2011 Pearson Education, Inc. Lecture prepared by Mindy Miller-Kittrell, University of Tennessee, Knoxville M I C R O B I O L O G Y WITH DISEASES BY TAXONOMY, THIRD EDITION Cell Structure and Function Chapter 3
Copyright © 2011 Pearson Education, Inc. Cell: the structural and functional unit of all living organisms (Cell theory by Schleiden and Schwann) Two Types of Cells: – Prokaryote (comes from the Greek words for “before nucleus”) – Lack a membrane around their DNA – No nucleus – Eukaryote (comes from the Greek words for “true nucleus”) – Have a membrane surrounding DNA – Nucleus Prokaryotic and Eukaryotic Cells
Copyright © 2011 Pearson Education, Inc. ProkaryoteEukaryote Ribosome Flagella Nucleoid Inclusion body Fimbria Cell membrane Cytoplasm Cell wall Glycocalyx Chloroplast Nucleolus Nucleus Nuclear membrane ER Golgi Mitochondria Cilia Nuclear pore Ribosome Plasmid
Copyright © 2011 Pearson Education, Inc. Prokaryote vsEukaryote Nucleoid region One chromosome No histones No membrane bound organelles 70S ribosomes Complex cell walls Binary fission Small size Bacteria, Archaea Nuclear membrane Paired chromosomes Histones Membrane bound organelles 80S ribosomes Simple or no cell walls Mitosis Larger size Fungi, Parasites
Copyright © 2011 Pearson Education, Inc. Prokaryotic Cell Average size : µm diam µm length Common shapes : Cocci, Rods, Spirals Most bacteria are monomorphic (one shape) A few are pleomorphic due to the environment
Copyright © 2011 Pearson Education, Inc. Prokaryote Cell Arrangements Determined by the planes in which it divides Pairs: diplo – Neisseria Chains: divide in 1 plane – Streptococcus, Streptobacillus Tetrads (4)- divide in 2 planes- Aerococcus Clusters: divide in multiple planes - Staphylococcus
Copyright © 2011 Pearson Education, Inc. External Structures of Prokaryotes Glycocalyx Flagella Fimbriae Pili Glycocalyx Flagella Fimbriae
Copyright © 2011 Pearson Education, Inc. Glycocalyx Viscous, sticky Gelatinous carbohydrate Made in cell & secreted Types: – Capsule is neatly organized and firmly attached to cell wall – Slime layer is unorganized and loosely attached to cell wall Purpose: – Protection against drying – Attachment to surfaces – Virulence – inhibits phagocytosis
Copyright © 2011 Pearson Education, Inc. Glycocalyces - Capsule & Slime Layer
Copyright © 2011 Pearson Education, Inc. Flagella Found in bacilli (rods) Long, semi-rigid appendages Purpose: – Motility (movement) Parts: – Flagellin in helix around hollow core – Hook for attachment – Basal body - anchors to the wall and membrane Figure 4.8
Copyright © 2011 Pearson Education, Inc. Flagella Purpose : motility Moves : by rotating flagella (like a propeller) – In liquid – run – tumble - run – On agar - swarms – Move toward or away from stimuli (taxis) Flagella proteins are H antigens – Used to identify organisms (e.g., E. coli O157:H7) – Differs by species/strain
Copyright © 2011 Pearson Education, Inc. Flagella Arrangement
Copyright © 2011 Pearson Education, Inc. Axial Filaments Found in spirochetes Endoflagella – – Anchored at one end of a cell – Form bundles spiraling around cell under a sheath Rotation causes cell to move
Copyright © 2011 Pearson Education, Inc. Found in gram negative bacilli Many, short, straight, thin filaments Made of protein - pilin Allow attachment Fimbriae
Copyright © 2011 Pearson Education, Inc. Pili Made of protein - pilin Longer than fimbriae Only 1 or 2 per cell Used to transfer DNA from one cell to another by conjugation
Copyright © 2011 Pearson Education, Inc. Cell Wall Complex, semi-rigid structure Prevents osmotic lysis, provides shape Made of peptidoglycan (in bacteria) Cell wall
Copyright © 2011 Pearson Education, Inc. Peptidoglycan- in bacterial cell walls Consists of repeating disaccharides – N-acetylglucosamine (NAG) & N-acetylmuramic acid (NAM) Linked by polypeptides – Includes amino acid isomer side chains attached to NAM
Copyright © 2011 Pearson Education, Inc. Gram-Positive cell walls Thick layer of Peptidoglycan Teichoic acids: – Lipoteichoic acid links to plasma membrane – Wall teichoic acid links to peptidoglycan
Copyright © 2011 Pearson Education, Inc.
Gram-Negative Cell Walls Thin layer of peptidoglycan in periplasmic space Outer membrane of phospholipids, lipoproteins, and lipopolysaccharides
Copyright © 2011 Pearson Education, Inc. Gram-Negative Outer Membrane Protection from phagocytes, complement, antibiotics O lipopolysaccharide antigen ( E. coli O157:H7) Lipid A is an endotoxin Porins (proteins) form channels through membrane
Copyright © 2011 Pearson Education, Inc. Comparison of Cell Walls
Copyright © 2011 Pearson Education, Inc. Gram-positive Gram-negative cell wallscell walls 1.Thick layer of peptidoglycan 2.No periplasmic space 3.Teichoic acids 4.No outer membrane 1.Thin layer of peptidoglycan 2.Periplasmic space 3.No teichoic acids 4.Outer phospholipid membrane
Copyright © 2011 Pearson Education, Inc. Atypical Cell Walls Acid-fast bacteria – Mycolic acid Mycoplasma – Lack cell walls – Sterols in plasma membrane Archaea – Wall-less, or – Walls of varying polysaccharides and proteins – Do not have peptidoglycan in cell walls
Copyright © 2011 Pearson Education, Inc. Cell Membrane Plasma membrane, Cytoplasmic membrane Composed of: –Phospholipid bilayer –Proteins Fluid mosaic model
Copyright © 2011 Pearson Education, Inc. Plasma Membrane Purpose Selective permeability: Regulates movement of substances in and out of cell ATP production
Copyright © 2011 Pearson Education, Inc. Bacterial Cytoplasmic Membranes Movement of molecules Active Transport – requires energy from the system Passive Transport – Passive processes – Diffusion – Facilitated diffusion – Osmosis
Copyright © 2011 Pearson Education, Inc. Passive processes of movement Figure 3.18
Copyright © 2011 Pearson Education, Inc. Osmosis Figure 3.19
Copyright © 2011 Pearson Education, Inc. Effects of solutions on cells Figure 3.20
Copyright © 2011 Pearson Education, Inc. Prokaryotic Cytoplasmic Membranes Function – Active processes – Active transport – Group translocation – Substance chemically modified during transport
Copyright © 2011 Pearson Education, Inc. Mechanisms of active transport Figure 3.21
Copyright © 2011 Pearson Education, Inc. Bacterial Cytoplasmic Membranes Animation: Active Transport: Overview
Copyright © 2011 Pearson Education, Inc. Bacterial Cytoplasmic Membranes Animation: Active Transport: Types
Copyright © 2011 Pearson Education, Inc. Group translocation Figure 3.22
Copyright © 2011 Pearson Education, Inc. Cytoplasm The substance inside the plasma membrane Thick, semi transparent Made of 80% water, enzymes, carbohydrates
Copyright © 2011 Pearson Education, Inc. Internal contents Nucleoid region – chromosomal DNA 70S Ribosomes – protein synthesis Plasmids – extrachromosomal DNA Inclusions – storage of polysaccharides, lipids for energy Cytosol – liquid portion of cytoplasm Figure 4.6a, b Nucleoid region Plasmid Ribosome
Copyright © 2011 Pearson Education, Inc. Ribosomes There are two subunits: a small one (30S), and a bigger one (50S). When a ribosome needs to be formed for translation, the subunits attach to each other and form a 70S unit. The "S" is a measure of the rate of sedimentation in centrifugation, rather than a measure of weight. That's why those two subunits put together are 70S, and not 80S. The subunits themselves are made of RNA and proteins.
Copyright © 2011 Pearson Education, Inc. Ribosomes
Copyright © 2011 Pearson Education, Inc. Endospores Produced by Bacillus, Clostridium Resting cells Resistant to desiccation, heat, and chemicals 1 cell – 1 spore NOT reproductive Sporulation or Sporogenesis : – Endospore formation (8-10hr) Germination : – Return to vegetative state
Copyright © 2011 Pearson Education, Inc. The formation of an endospore Figure
Copyright © 2011 Pearson Education, Inc. Table 10.2