Chapter 1 Morphology and properties of bacteria Belong to the prokaryote kingdom,the absence of a...

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Transcript of Chapter 1 Morphology and properties of bacteria Belong to the prokaryote kingdom,the absence of a...

  • Section 1 Size and shapes of bacteriaThe unit of measurement is micrometer (m) Sizes

  • basic shapesSpherical: coccusStraight rod: bacillusCurved or spiral: vibrio or spirillumUncharacteristic (e.g., filamentous, pleomorphic, etc.)

  • Arrangements cocci In one plane:Diplococcus Streptococcus

    In two planes: Tetrad

    In three planes: Sarcina

    In random planes:Staphylococcus

  • Cell Arrangement

  • 1diplococcus S. pneumoniaegonococcus

  • 2streptococcus -hemolytic streptococcus

  • 3staphylococcusS. aureus

  • ArrangementsBacilliOnly in one planeBacillus StreptobacillusCoccobacillus

  • bacillus dysenteriae (gram staining)

  • Bacillus tuberculosis(acid fast stain)

  • ArrangementsSpiral bacteriain single cells

  • Section 2 Structures of Bacterial cellsBasicCell wallCellular membraneCytoplasmnucleoidSpecialCapsuleFlagellumPilusSpore

  • Bacterial structure

  • Cell wall-Components

  • Cell wall-ComponentsPeptidoglycan Backbone: alternating N-acetylmuramic acid (NAM) and N-acetylglucosamine (NAG)

    A set of identical tetrapeptide side chains A set of identical pentapeptide cross bridges(G+)

  • peptidoglycanN-acetylglucosamineN-acetylmuramic acidStaphylococcus aureusE.coliLysozyme breaks this bondpentaglycine bridgeL-alaD-gluL-lysD-alaD-alaL-alaD-glu m-DAPD-alaD-alapenicillin

  • Cell wall-ComponentsTeichoic acid: Organisms: G+ bacteriaTypes: the wall teichoic acidthe membrane teichoic acidFunction: acts as a specific antigenic determinantRelation to pathogenicity

  • Wall teichoic acid(LTA)

  • Cell wall-ComponentsOuter membrane Organisms: G- bacteria Composition: Lipoprotein Lipid bilayer Lipopolysaccharide (LPS): lipid A core polysaccharide O-polysaccharide

  • Outer membrane

    Functions:prevents toxic materials from enteringfunctions as a harmful endotoxinpossesses the property of antigenic specificity

  • GRAM POSITIVEGRAM NEGATIVECytoplasmCytoplasmLipoteichoic acidPeptidoglycan-teichoic acid Cytoplasmic membraneInner (cytoplasmic) membraneOuter MembraneLipopolysaccharidePorinBraun lipoproteinPeriplasmic space

  • Properties of the cell walls of Gram-positive and Gram-negative bacteria

  • Cell wallFunctionsgives the bacterium its shape Protecting the cellConstituting major surface antigensPermitting the free diffusion of low-molecular-weight hydrophilic compoundsHaving pathogenic material


  • The mechanism of some antibiotics and enzymes killing bacteria penicillin: Binds to transpeptidase and blocks the formation of whole cell wall of Gram-positive bacteriaLysozyme: Destroys the peptidoglycan by cleaving the -1,4 glycosidic bonds between NAM and NAG G-G+

  • G+ and G-N-acetylglucosamineN-acetylmuramic acidStaphylococcus aureus

    E.coliLysozyme breaks this bondpentaglycine bridgeL-alaD-gluL-lysD-alaD-alaL-alaD-glu m-DAPD-alaD-alapenicillin

  • Penicillin and cephalosporin

    Results of enzyme digestion:Protoplast Spheroplast

  • L formsDefinition: bacteria that their peptidoglycan is destroyed or lost by various factors but they can survive under highly osmotic environment.Types: Protoplasts(G+) and spheroplasts (G-)Shape: polymorphism Staining property: gram-negative Grow environment: high osmotic Pathogenicity: chronic

  • A.Colony of normal bacteria B.fried egg colony of L-form bacteriaC.Granular colony of L-form bacteria D.filamentous colony of L-form bacteria

  • L forms are able to grow and divide

    Caused by antibiotic

    Some L forms can revert to the normal form upon removal of the inducing stimulus

  • producing chronic infections,being resistant to antibiotic treatment.

  • B.Cell membrane(Cytoplasmic membrane)Composition: composed primarily of proteins and lipids. It is a thin,elastic cytoplasmic membrane,which is 510nm thick

    Visible in some ultrathin sections

    Examined with the electron microscope

  • Function

    active transport

    respiratory chain component



  • Epithelial cellThe bacteria are classified by shapes into three basic groups:coccus,bacillus and spiral bacterium,the bacterial shape is determined by its rigid cell wall.Located external to the cytoplasm membrane.according to their response to the gram staining procedureperiplasmLLL