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Bacterial Cell Structure (continued)

Bacterial Cell Structure (continued). You are here. Gram negative cell wall. Outer membrane. Lipid bilayer membrane: Asymmetric Inner and outer leaflets Inner leaflet made of phospholipids; outer leaflet is made of lipopolysaccharide (LPS) LPS = endotoxin

alexandra-brennan
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Bacterial Cell Structure (continued)

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  1. Bacterial Cell Structure (continued) You are here.

  2. Gram negative cell wall

  3. Outer membrane • Lipid bilayer membrane: Asymmetric • Inner and outer leaflets • Inner leaflet made of phospholipids; outer leaflet is made of lipopolysaccharide (LPS) • LPS = endotoxin • Proteins for transport of substances • Porins: tri-subunit, transmembrane proteins • Barrier to diffusion of various substances • Lipoprotein: anchors outer membrane to PG

  4. Structure of LPS extends from cell surface. contains odd sugars e.g. KDO. Gln-P and fatty acids take the place of phospholipids. www.med.sc.edu:85/fox/ cell_envelope.htm

  5. Periplasmic Space www.arches.uga.edu/~emilyd/ theory.html

  6. Periplasm • The periplasm is the “stuff” in that space, present in Gram + bacteria also. • A hydrated gel including the PG • Binding proteins that aid in transport • Hydrolytic enzymes for breaking down large molecules • Chemoreceptor proteins that help direct swimming • Enzymes for synthesizing PG, OM

  7. Glycocalyx: capsules and slime layers “Sugar covering”: capsules are firmly attached, slime layers are loose. Multiple advantages to cells: prevent dehydration absorb nutrients protection from predators, WBCs protection from biocides (as part of biofilms) attachment to surfaces and site of attachment by others. S-layers are highly structured protein layers that function like capsules cell capsule www.activatedsludge.info/ resources/visbulk.asp

  8. Fimbriae and pili Both are appendages made of protein Singular: fimbria, pilus Both used for attachment Fimbriae: to surfaces (incl. host cells) and other bacteria. Pili: to other bacteria for exchanging DNA (“sex”). www.ncl.ac.uk/dental/oralbiol/ oralenv/images/sex1.jpg

  9. Fimbriae and pili-2 http://www.mansfield.ohio-state.edu/~sabedon/006pili.gif

  10. Flagella • Flagella: protein appendages for swimming through liquid or across wet surfaces. • Rotate like propellers. • Different from eukaryotic flagella. • Arrangements on cells: • polar, • Lophotrichous, • amphitrichous, • peritrichous. www.ai.mit.edu/people/ tk/ce/flagella-s.gifwww.bmb.leeds.ac.uk/.../icu8/ introduction/bacteria.html

  11. Flagellar structures www.scu.edu/SCU/Departments/ BIOL/Flagella.jpg img.sparknotes.com/.../monera/ gifs/flagella.gif

  12. Runs and Tumbles: bacteria find their way http://www.bgu.ac.il/~aflaloc/bioca/motil1.gif

  13. Motility revisited • Flagella: protein appendages for swimming through liquid or across wet surfaces. • Axial filament: a bundle of internal flagella • Between cell membrane and outer membrane in spirochetes • Filament rotates, bacterium corkscrews through medium • Gliding • No visible structures, requires solid surface • Slime usually involved.

  14. Axial filaments http://images.google.com/imgres?imgurl=http://microvet.arizona.edu/Courses/MIC420/lecture_notes/spirochetes/gifs/spirochete_crossection.gif&imgrefurl=http://microvet.arizona.edu/Courses/MIC420/lecture_notes/spirochetes/spirochete_cr.html&h=302&w=400&sz=49&tbnid=BOVdHqepF7UJ:&tbnh=90&tbnw=119&start=1&prev=/images%3Fq%3Daxial%2Bfilament%2Bbacteria%26hl%3Den%26lr%3D%26sa%3DG

  15. Gliding Motility Movement on a solid surface. No visible organelles of locomotion. Cells produce, move in slime trails. Unrelated organism glide: myxobacteria, flavobacteria, cyanobacteria; appear to glide by different mechanisms. Cells glide in groups, singly, and can reverse directions. http://cmgm.stanford.edu/devbio/kaiserlab/about_myxo/about_myxococcus.html

  16. From the membrane in: the bacterial cytoplasm • Cytoplasm is a gel made of water, salts, LMW molecules, and lots of proteins. • DNA = nucleoid, w/ proteins • Plasmids = small circular DNA • Ribosomes: site of protein synthesis. Cytoplasm may also contain inclusions, gas vacuoles, extended membrane systems, or magnetosomes. But generally NO membrane-bound organelles.

  17. Inclusions and granules • Storage molecules found as small bodies within cytoplasm. • Can be organic (e.g. PHB or glycogen) or inorganic (Sulfur, polyphosphate. • PHB, a type of PHA, degradable plastic (polyester); glycogen, a polymer of glucose. • Sulfur, a metabolic by-product; polyphosphate, polymer of PO4 http://www.accessexcellence.org/WN/SUA12/marg499.html

  18. Magnetosomes Membrane coated pieces of magnetite, assist bacteria in moving to microaerophilic environments. An organelle? North is down. Magnetospirillum magnetotacticum www.calpoly.edu/~rfrankel/ mtbphoto.htmlhttp://geoweb.tamu.edu/courses/geol101/lab/topo_maps/IMG00006.GIF

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