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Slide 1Cell WallPeptidoglycan(note)Cross Linked PetidoglycanPeptidoglycan (http://sp.uconn.edu/~terry/images/other/peptidoglycan.gif)Cross LinkingGram + and Gram -Gram + Cell WallGram – Cell WallLipopolysaccharide (LPS)PeriplasmPenicillinUnusual Cell WallsBacteria w/o a Cell WallCell MembranePhospholipid (http://bioweb.wku.edu/pix/cells/P-lipid2.gif)Phospholipid bilayer (http://www.rcscsd.org/apbio/notes_membranes.htm)Phospholipid BilayerHow do bacteria aquire most of their raw materials ?Group TranslocationHow do bacteria sense and respond to their environment ?Cell Membrane (http://www.rdc.ab.ca/scottpsych/website/student/475chp1.htm)Bacterial ChromosomeSlide 25Slide 26“extra” chromosomal DNA PlasmidsRibosomesEndosporesSlide 30Lecture 1bBacterial Cell StructureCell WallProtects the cell from osmotic shock. ( a lot of water can kill you. It will swell up the cell and blow up) Composed of: peptidoglycan (unique to bacteria)( not found in humans, plants, and fungi and is a good anitbiotics) peptido – peptide – proteinglycan – glucose - carbohydrateNext inner most part of bacterial cellPeptidoglycanComposed of long chains of alternating : N-acetylmuramic acid (NAM) andN-acetylglucosamine (NAG)Attached to each NAM is a tetrapeptide(NAM - L-Alanine – D-Glutamic Acid – Diaminopimelic Acid – D-Alanine)…NAM-NAG-NAM-NAG….…NAM-NAG-NAM-NAG….(note)Diaminopimelic Acid is a derivative of the amino acid Lysine and is found nowhere else in nature except in the bacterial cell wall !alsoD-amino acids are not used to make proteins (why Nutrasweet has no calories)Cross Linked PetidoglycanAdjacent Glycan chains can be “cross-linked” to each other in two different ways:1) A peptide inter-bridge between the Diaminopimelic Acid of one glycan chain and the D-Alanine of another (the composition of this inter-bridge varies between species)(Gram+)2) The tetrapeptides are joined directly(Gram-)Peptidoglycan(http://sp.uconn.edu/~terry/images/other/peptidoglycan.gif)gram+ inter-bridgeCross Linking(imagine)Rubber cement GRAM -(weak, soluble…)Rubber Car tire ( gram+ and lasts longer) (strong, tough, insoluble…)Gram + and Gram -The cell wall of some bacteria respond differently to a particular staining procedure called the GramNot surprisingly, this behavior is the result of structural differences between these bacteria.Gram + Cell WallThick peptidoglycan layer (~30 layers) – peptide inter-bridgeTeichoic Acids – project outward from peptidoglycan layer – immunogenicLipoteichoic Acids – project inward from peptidoglycan layer to cytoplasmic membrane – anchorFully permeableGram – Cell WallThin peptidoglycan layer – no peptide inter-bridgeOuter Membrane – unique structure – bilayer of phospholipid (inner) / lipopolysaccharide (outer) - Porins span the outer membrane (size exclusion) – protects from some antibioticsResistance to certain antiboticLipopolysaccharide (LPS)Heat stable Endotoxin composed of : elicits all the symptoms of a bacterial infectiondifferent types of LPS  species IDImmunegeticPeriplasm(just underneath the outer membrane)houses secreted degradative enzymes(pathology)Stored temporarily in periplasmPenicillin(the first broad spectrum antibiotic)Disrupts cross-linking between glycan moleculesMore effective against Gram + because Penicillin is excluded by porins in Gram-(also resistance due to the evolution of penicillinase)(Makes pepto layer weak)Unusual Cell WallsMycob acterium - largely composed of mycolic acid making them appear waxy and more resistant to chemicals, dehydration, antibiotics (pathology)(TB)Propels water and anything in water more resistant to ecoliBacteria w/o a Cell WallMycoplas mas(lack a cell wall altogether)pleomorphicpenicillin resistantCell Membraneregulates transport into/out of the cell~ 50 % phospholipid~ 50 % integral membrane proteins(underneath cell wall) Embedded in membranePhospholipid(http://bioweb.wku.edu/pix/cells/P-lipid2.gif)Non-polar regionLong hydrocarbon chainsPhospholipid bilayer(http://www.rcscsd.org/apbio/notes_membranes.htm)If you mix them up with water it spontaneously form all membranePhospholipid BilayerFreely permeable to water, dissolved gases, and small hydrophobic molecules by :simple diffusion(high concentration  low concentration)(Water can go in and out) (Can go into/out of cell )Hydoplic molecules are too big to go through cells. : glucose, amino acidsHow do bacteria aquire most of their raw materials ?Transport ProteinsSymporters – transport of two substances in the same direction (i. e. sugars)Antiporters – transport of two substances in opposite directions (i.e. Na+/ H+, H+/antimicrobials) (anitbiotics) Uniporters – transports one substance in one direction (either in or out) (i.e. cations +) (potassium, calcium)Group Translocation(clever – especially for bacteria)The substance is chemically altered during transport (phosphotransferase system) (i.e. glucose and other sugars)The cell can soak up all the glucose by converting into glucose-phosphateHow do bacteria sense and respond to their environment ?Receptors – transduce chemical signals from outside the cell to inside the cellCell Membrane(http://www.rdc.ab.ca/scottpsych/website/student/475chp1.htm)Receptor proteinBacterial ChromosomeA single, circular, supercoiled, double stranded DNA molecule (1 mm long)the cell is ~1 m long (1/1000X)one per cellreplicates only when the cell divides1000-5,000 Kbp (relatively small) ( compared to human chromosomes) Allows a larger bacterial cellBacterial Chromosomesingle – where one gene goes so do all the others (little variation)circular – easier to replicate than linear (humans have linear) dsDNA – like ours – replicates like ours1-5kb – genetically simple – few genes – easier to understandBacterial Chromosomehttp://www.bact.wisc.edu/themicrobialworld/structure.html“extra” chromosomal DNA Plasmidsvery small (2-10 Kbp), autonomously replicating, circular, double stranded DNA moleculesvery small - carry a few to several hundred ‘non-essential’ genes (AbR, pathogenicity)autonomously replicating --- > 1000 copies / cellCan be transferred from one bacterium to another (intra/inter species - by multiple mechanisms)Even when cell doesn’t replicateRibosomesThe molecular machine that assembles amino acids into proteins.comprised of ~ 54 proteins and ~ 3 RNAssufficiently different from Eukaryotic ribosomestarget of many antibioticsInside bacterial cell There


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KSU BSCI 20021 - Bacterial Cell Structure

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