The Basic Structures of Bacteria Anatomy and Physiology PDF

10/7/2023 ‫وزارة التعليم العالي و البحث العلمي‬ ‫ كلية الصيدلة‬/ ‫جامعة العميد‬ ‫فرع العلوم المختبرية‬ The Basic Structures of Bacteria Anatomy and Physiology Abdul sattar AL-Saeedi...

10/7/2023 ‫وزارة التعليم العالي و البحث العلمي‬ ‫ كلية الصيدلة‬/ ‫جامعة العميد‬ ‫فرع العلوم المختبرية‬ The Basic Structures of Bacteria Anatomy and Physiology Abdul sattar AL-Saeedi M.Sc. Medical Microbiology Ph.D. in medical microbiology (Molecular virology) Objectives The students will be able to  Define the bacteria  Describe the bacterial cell wall.  Compare between Gram-positive and Gram-negative bacteria.  Distinguish types of flagellums.  Describe the function of fimbriae and pili.  Classify bacterial according to shape. 1  10/7/2023 Introduction Bacteria are single-celled prokaryotes, their DNA forming a long circular molecule, but not contained within a defined nucleus. Many are motile, using a unique pattern of flagella. They reproduce by binary fission, often at very high rates, and show a wide range of metabolic patterns, both aerobic and anaerobic. 1 2 2  10/7/2023 1- Cell Wall The cell wall is the outermost component common to all bacteria (except Mycoplasma species, which are bounded by a cell membrane, not a cell wall). Some bacteria have surface features external to the cell wall, such as capsule, flagella, and pili, which are less common components and are discussed next. The cell wall is located external to the cytoplasmic membrane and is composed of peptidoglycan. 3 Peptidoglycan 1.Unique macromolecule composed of a repeating framework of long glycan chains cross-linked by short peptide fragments. 2.Provides strong, flexible support to keep bacteria from bursting or collapsing because of changes in osmotic pressure 4 3  10/7/2023 Cell Wall Bacteria are classified according to their cell wall to Gram-positive Gram Bacteria Cell Wall negative without cells cell walls 5 Gram-positive Cell Wall The gram-positive cell wall contains two major components, peptidoglycan and teichoic acids, plus additional carbohydrates and proteins, depending on the species. 6 4  10/7/2023 2. Gram negative cells The second kind of cell wall found in bacteria, the gram-negative cell wall. In gram-negative cells, the amount of peptidoglycan has been greatly reduced, with some of it forming a single-layered sheet around the cell and the rest in a gel-like substance, the periplasmic gel, with little cross-linking. 3. Bacteria without cell walls For example Mycoplasma species 7 8 5  10/7/2023 2- Flagellum Specialized appendage attached to the cell by a basal body that holds a long rotating filament. The movement pushes the cell forward and provides motility. Consist of three Parts : 1. Filament: long, thin, helical structure composed of proteins 2. Hook: curved sheath 3. Basal body: stack of rings firmly anchored in cell wall 9 10 6  10/7/2023 Flagellar arrangements 1. Monotrichous: single flagellum at one end 2. Lophotrichous: small bunches arising from one end of cell 3. Amphitrichous: flagella at both ends of cell 4. Peritrichous: flagella dispersed over surface of cell, slowest 11 12 7  10/7/2023 Axial filaments (Endoflagella) Periplasmic, internal flagella, enclosed between cell wall and cell membrane of spirochetes Motility Example Treponema pallidium causes syphilis 13 14 8  10/7/2023 3- Fimbriae  Fine hair like bristles from the cell surface  Found on many Gram-negative and some Gram-positive bacteria  Thinner and shorter than a flagellum  Function in adhesion to other cells and surfaces  Fimbriae are one of the primary mechanisms of virulence for E. coli, Bordetella pertussis, Staphylococcus and Streptococcus bacteria. 15 16 9  10/7/2023 Pili Rigid tubular structure found on the surface of bacteria  Found only in Gram negative cells  Functions 1. Joins bacterial cells for DNA transfer (conjugation) 2. Adhesion 17 18 10  10/7/2023 Glycocalyx  Many bacterial species secrete an adhering layer of polysaccharides, or polysaccharides and small proteins, called the glycocalyx.  The layer can be thick and covalently bound to the cell, in which case it is known as a capsule.  A thinner, loosely attached layer is referred to as a slime layer. 19 20 11  10/7/2023 21 Functions Attachment Inhibits killing by white blood ells 22 12  10/7/2023 FIGURE Haemophilus influenzae disease, cellular view. Organisms attach to epithelial cells using pili and outer membrane proteins (OMPs). Invasion takes place between cells by disruption of cell–cell adhesion molecules. In the submucosa, the capsule allows the bacteria to evade phagocytosis and enter the bloodstream. PMNs, polymorphonuclear neutrophils. 23 Pathogen- association capsule molecular patterns Host cell Endocytic pattern recognition receptors 24 13  10/7/2023 Cytoplasm Dense gelatinous solution of sugars, amino acids, & salts. 70-80% water. Serves as solvent for materials used in all cell functions. 25 Chromosome single, circular, double-stranded DNA molecule that contains all the genetic information required by a cell. DNA is tightly coiled around a protein, aggregated in a dense area called the nucleoid 26 14  10/7/2023 Plasmids Small circular, double-stranded DNA Free or integrated into the chromosome Bacterial DNA Plasmids Duplicated and passed on to offspring Not essential to bacterial growth & metabolism May encode antibiotic resistance, tolerance to toxic metals, enzymes & toxins. 27 Ribosomes The ribosomes are built from RNA and protein and are composed of a small subunit (30S) and a large subunit (50S). For proteins to be synthesized, the two subunits come together to form a 70S functional ribosome. Some antibiotics, such as streptomycin and tetracycline, prevent bacterial and archaeal ribosomes from carrying out protein synthesis. 28 15  10/7/2023 Inclusions, granules:  Intracellular storage bodies.  Bacterial cell can use them when environmental sources are depleted.  Examples: glycogen, gas vesicles for floating, sulfur and polyphosphate granules. 29 Endospores Endospores are dormant structures that can endure times of nutrient stress..A few gram- positive bacterial species, especially soil bacteria belonging to the genera Bacillus and Clostridium, produce highly resistant structures called endospores or, simply, spores. 30 16  10/7/2023 Shapes of bacteria Bacteria can be classify according to shape to three groups Shapes of bacteria Cocci, are round Bacilli, are rods Spirochetes are spiral shaped 31 33 17  10/7/2023 Thank Any question? 18