Lecture 1. Cell Structure And Function In Bacteria PDF

Y1M1, Infection and Immunity "Structure and Function of Bacterial Cells: Roles and Characteristics of Cellular Components" Department of Microbiology and Immunology Yonsei University College of Medicine Seoul, Korea Sang Sun...

Y1M1, Infection and Immunity "Structure and Function of Bacterial Cells: Roles and Characteristics of Cellular Components" Department of Microbiology and Immunology Yonsei University College of Medicine Seoul, Korea Sang Sun Yoon, PhD [email protected] Dr. Woubijig Dechasa Classification of living organisms · If you see a creature that is alive, it is either Eukaryote or Prokaryote.  Classification of living organisms Prokaryotes are further divided into Bacteria and Archea. Ex. Thermus aquaticus Archeas live under some of the most extreme environments on the planet. 1) rift vents in the deep sea at temperatures well over 100 °C 2) hot springs (such as the ones pictured above) 3) extremely alkaline or acid waters. 4) inside the digestive tracts of cows, where they produce methane 5) anoxic muds of marshes and at the bottom of the ocean 6) petroleum deposits deep underground. For more information, please visit http://www.ucmp.berkeley.edu/archaea/archaea.html  Three major domains of life parasites Proteobacteria: second largest group of bacteria that contains 1534 species all gram-negatives  The hallmarks of living organism 1. Metabolism 4. Communication 2. Differentiation 5. Movement 6. Evolution 3. Reproduction Bacteria, friend or foe? Characteristics of Bacteria 1. Unicellular microorganisms 2. ~micrometer in length 3. Ubiquitous (40 million bacterial cells in a gram of any given soil) 4. Total of 5×1030 bacteria on Earth 5. Less than 1 % of the entire species are culturable. 6. Ten times as many bacterial cells as human cells in our own body 7. Only a small portion of bacterial species is of medical importance Pathogenic bacteria of clinical importance ·Vibrio cholerae Gut microbiota The Black Death, 1347-1350 In Europe 14th C global population: ~450 M to ~350 M  Black Death (Plague) Boccaccio's description about the Black death "In men and women alike it first betrayed itself by the emergence of certain tumours in the groin (사타구니) or armpits (겨드랑이), some of which grew as large as a common apple, others as an egg...From the two said parts of the body this deadly gavocciolo soon began to propagate and spread itself in all directions indifferently; after which the form of the malady began to change, black spots or livid making their appearance in many cases on the arm or the thigh or elsewhere, ~~~~"[ A flea infected with Yersinia pestis, shown as a dark mass. The foregut of this flea is blocked by a Y. pestis biofilm, which is a prerequisite for efficient transmission.  Spontaneous Generation vs. Germ Theory In 1859, Louis Pasteur conducted a series of experiments that conclusively disproved the theory of spontaneous generation, which was the belief that living organisms could arise from non-living matter. Pasteur's work was pivotal in establishing the Germ Theory of Disease, which posits that many diseases are caused by microorganisms. This marked a major turning point in microbiology and medicine, leading to the development of sterilization, pasteurization, and vaccines. Koch’s postulate The Nobel Prize in Physiology or Medicine 1905 was awarded to Robert Koch "for his investigations and discoveries in relation to tuberculosis". Koch performed repeated subcultures of Bacillus anthracis (the anthrax bacillus) in pure cultures and discovered that when the bacteria were inoculated into other animals, they exhibited the same symptoms. He then proposed that to prove a specific pathogen as the causative agent of a particular disease, the following four criteria must be met: i) The pathogen must be found in animals suffering from the disease but not in healthy animals. ii) The pathogen must be isolated from the diseased animal and grown in pure culture. iii) The cultured pathogen must cause the same disease when introduced into a healthy, susceptible animal. iv) The pathogen must be re-isolated from the experimentally infected animal and shown to be the same as the original pathogen. Koch's postulates led to the discovery of the causative agents of major bacterial diseases over the next 20 years, marking the golden age of bacteriology. During this time, pathogens such as Bacillus anthracis (anthrax), Corynebacterium diphtheriae (diphtheria), Salmonella typhi (typhoid fever), Neisseria gonorrhoeae (gonorrhea), Clostridium perfringens (gas gangrene), Shigella (dysentery), Clostridium tetani (tetanus), and Treponema pallidum (syphilis) were identified. Cell walls of bacteria Structure of the cytoplasmic membrane Structure of a phospholipid bilayer The major functions of the cytoplasmic membrane Although structurally weak, the cytoplasmic membrane has many important cellular functions Comparative permeability of membranes to various molecules  Membrane Transport Systems At least three types of transporters are known: simple transporters, phosphotransferase-type transporters, and ABC (ATP-binding cassette) transporters. only a membrane-spanning protein Series of proteins in the transport event Substrate-binding protein Membrane transporter ATP hydrolyzing protein Structure of membrane-spanning transporters and types of transport events In prokaryotes, membrane spanning transporters typically contain 12 α-helices that align with each other in a circle to form a channel through the membrane. Shown here are three individual transporters, each showing a different type of transport event. For antiporters and symporters, the cotransported molecule is shown in yellow. Mechanism of the phosphotransferase system of E. coli. For glucose uptake, the system consists of five proteins: Enzyme (Enz) I; Enzymes IIa, IIb, and IIc, and HPr. Sequential phosphate transfer occurs from phosphoenolpyruvate (PEP) through the proteins shown to Enzyme IIc. The latter actually transports (and phosphorylates) the sugar. Proteins HPr and Enz I are nonspecific and involved in the transport of any sugar. The Enz II components are specific for a particular sugar. Catabolite repression Mechanism of an ATP-Binding Cassette (ABC-type) transporter The periplasmic binding protein has high affinity for substrate, the membrane-spanning protein is the transport channel, and the cytoplasmic ATP-hydrolyzing protein supplies the energy for the transport event. Peptidoglycan layer Structure of one of the repeating units of the peptidoglycan cell wall structure, the glycan tetrapeptide The structure given is that found in Escherichia coli and most other gram-negative Bacteria. In some Bacteria, other amino acids are found. R Cross linking of peptidoglycan layers (a) No interbridge is present in E. coli and other gram-negative Bacteria. (b) The glycine interbridge in S. aureus (gram-positive). (c) Overall structure of peptidoglycan. G, N-acetylglucosamine, M, N-acetylmuramic acid.  The gram-negative cell wall. Note that although the outer membrane is often called the "second lipid bilayer," the chemistry and architecture of this layer differ in many ways from that of the cytoplasmic membrane. Arrangement of lipopolysaccharide, lipid A, phospholipid, porins, and lipoprot ein in the outer membrane. Structure and function of the prokaryotic flagellum in gram-negative Bacteria L ring is embedded in the LPS P ring in peptidoglycan. MS ring is embedded in the cytoplasmic membrane. C ring in the cytoplasm. A narrow channel exists in the rod and filament through which flagellin molecules diffuse to reach the site of flagellar synthesis. The Mot proteins function as the flagellar motor, whereas the Fli proteins function as the motor switch. The flagellar motor rotates the filament to propel the cell through the medium. Structure of the lipopolysaccharide of gram-negative Bacteria The precise chemistry of lipid A and the polysaccharide components varies among species of gram-negative Bacteria. But the sequence of major components (lipid A-KDO-core-O-specific) is generally uniform. The O-specific polysaccharide varies among species. KDO, ketodeoxyoctonate; Hep, heptose; Glu, glucose; Gal, galactose; GluNac, N-acetylglucosamine; GlcN, glucosamine; P, phosphate. Glucosamine and the lipid A fatty acids are linked by an amine ester bond. The lipid A portion of LPS can be toxic to animals and comprises the endotoxin.