J210 Lecture 3 Prokaryotes / Eukaryotes ContinuedSlide 2Gram StainCell Envelope Structure Of A Gram-Positive (G+) BacteriumCell Envelope Structure Of A Gram-Negative (G-) BacteriumSlide 6Slide 7Gram Staining ProcedureSlide 9How does it work?Slide 11Peptidoglycan subunitsMedical significance of PGSlide 14Medical Relevance Of LPS (Endotoxin)What is an endospore? Why is it stable?Slide 17Slide 18Slide 19Spore-formation in Fungi.Cyst-Formation in ProtozoaMotility in ProtozoaHow prevalent are deaths due to protozoan infections?Slide 24What is a bacterial virus?Slide 26Slide 27Slide 28J210Lecture 3Prokaryotes / EukaryotesContinuedStructure of Prokaryotic cellsStructure of Prokaryotic cellsGram StainGram StainBacillus cereusE. coliGram Positive:dark purple/blueGram Negative:pinkCell Envelope Structure Of A Gram-Positive (G+) BacteriumCell Envelope Structure Of A Gram-Negative (G-) BacteriumRecognize how the 2 types of bacterial cell walls differ•Thickness of peptidoglycan (PG) layer•Presence of outer membrane layer in G (-) only Recognize how the 2 types of bacterial cell walls differ•Thickness of peptidoglycan (PG) layer•Presence of outer membrane layer in G (-) onlyGram Staining ProcedureGram Stain •differentiating the 2 categories of bacterial cell wallGram Stain •differentiating the 2 categories of bacterial cell wallHow does it work?Gram Stain differentiates based on the structure of the cell wall:Gram NegativeGram PositivePolysaccharide backbonePolypeptide bridgeshttp://www.youtube.com/watch?v=-sct8GUye-0&feature=related;PG illustrationStructure of Peptidoglycan (PG)A mesh similar to fabric consisting of:1. Polysaccharide (glycan) backbone2. polypeptide cross-bridgesStructure of Peptidoglycan (PG)A mesh similar to fabric consisting of:1. Polysaccharide (glycan) backbone2. polypeptide cross-bridgesPeptidoglycan subunitsMedical significance of PG•PG is present only in bacteria–Target for antibiotic drugs •Penicillin (antibiotic) prevents synthesis of PG causing bacteria to burst•Lysozyme, an enzyme present in tear secretions and phagocytic granules, which breaks up the PG backboneBacteriumLipopolysaccharide (LPS)•Also called endotoxin•Consists of 3 layers•Very hydrophobic lipid rich inner layer called Lipid A•Toxic part of the molecule•Polysaccharide middle layer (Core)•Polysaccharide outer layer (O side chain) Basic structure of LPSGram-negativeBacteria have outer membrane with LPSMedical Relevance Of LPS (Endotoxin)•Lipid A is toxic in humans causing endotoxic (septic) shock–Fever, release of cytokines (IL-1, IL-6, TNF), can lead to death due to septic shock•Changing sequence of O-side chain make bacteria able to make new strainsSeptic (endotoxic) shock patientsWhat is an endospore? Why is it stable?•Most stable living thing known•A survival strategy by certain Gram positive bacteria is the formation of endospores which is formed in response to harsh conditions including nutrient deprivation –It allows the bacterium to produce a dormant and highly resistant cell to preserve the it’s genetic material in times of extreme stress–Resists drying, freezing, boiling, Ultraviolet, time•Once inculcated in nutrient rich environment, endospores germinate and produce the original organismThe outer proteinaceous coat surrounding the spore provides much of the chemical and enzymatic resistance. Beneath the coat resides a very thick layer of specialized peptidoglycan called the cortex. Core contains the genetic materialBacteria divide by binary fission repeatedly until they run out of nutrients http://www.youtube.com/watch?v=3cD3U2pgb5w&feature=relatedhttp://www.youtube.com/watch?v=J6akNYlkehY&feature=relatedHarsh conditions Process of endospore formation (sporulation) Gram-positive bacteria only form endospores under harsh conditions•ONLY Gram (+) bacteria produce endospores–Example: Clostridium tetani•Endospore-forming Gram positive rods present in soil•Step on a dirty nail•Spores germinate deep within the tissue•Fully grown bacteria release toxin which causes the disease tetanus (lock jaw)Lock jaw caused by C. tetaniLock jaw caused by C. tetaniSpore-formation in Fungi.•Fungi have walls but comprised of chitin (a different polysaccharide). •Fungi have spores but much less stable than bacterial spores. –Stable to drying but not boiling–May survive several years–Fungal spores can circulate in the air and may cause allergic rhinitis when inhaledCyst-Formation in Protozoa•Protozoa are a large group of eukaryotic, single celled organisms, which lack a rigid cell wall.•Protozoa are usually free living and can be found in a variety of freshwater and marine environments and the soil•Many are parasitic in other animals, including humans•Some protozoa can form a cyst which is a dormant stage (eg. Amoeba).–This occurs in response to adverse conditions such as lack of food. –The cyst is a protective stage with a highly condensed cytoplasm and resistant cell wall usually passed in the fecesMotility in Protozoa•Protozoa, one-celled organism are characterized by motility to 3 groups1. Flagellates2. Ciliates3. Non-motile•Most multicellular parasites (eg. helminthes: worms) are also motile–helps them infect usCiliatesCiliatesFlagellatesFlagellatesHow prevalent are deaths due to protozoan infections?•Mostly in underdeveloped countries–5 million deaths/yr in world. –1 billion infected.Viruses have capsids•Viruses are NOT cells, so no cell wall.•All have a protein coat (capsid)•Some viruses also have a membrane cover over the protein coat (enveloped viruses)Enveloped virusEnveloped virusNaked virusesNaked virusesWhat is a bacterial virus?Virus that infect bacteria only are called bacteriophage or phageStructure of bacteriophage T4Structure of bacteriophage T4Life Cycle of BacteriophageLife Cycle of Bacteriophage•The genus name can hint at the shape.•Staphylococcus aureus•Streptococcus pneumoniae•Bacillus anthracis•Species often named for disease or discoverer–Streptococcus pneumoniae causes pneumonia–Borrelia Burgdorferi, named by Willi Burgdorfer, causes Lyme disease•Names are often abbreviated–Escherichia coli becomes E. coli–Staphylococcus aureus becomes S. aureus•By convention, genus and species are italicised or underlined–E. coli or E. coliThe binomial system for naming includes both genus and speciesThe binomial system for naming includes both genus and speciesStrain and