Ways to think about peptidoglycan 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 cell_envelope.htm extends from cell surface. contains odd sugars e.g. KDO. Gln-P and fatty acids take the place of phospholipids. 5

Periplasmic Space theory.html 6

Periplasm The periplasm is the “stuff” in that space, –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 Must be in Gram + bacteria also. 7

Glycocalyx: capsules and slime layers resources/visbulk.asp capsule cell “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. 8

Non-Carbohydrate layers S Layers –Crystalline, protein layers –Found widely in Archaea, also in G- and G+ Polypeptide capsule –B. anthracis has a poly D-glutamic acid capsule TEM image of a freeze-etching preparation of a bacterial cell exhibiting an S-layer with square (p4) lattice symmetry. Bar, 100nm 9

Fimbriae and pili oralenv/images/sex1.jpg 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”). 10

Fimbriae and pili

Flagella tk/ce/flagella-s.gif introduction/bacteria.html 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. 12

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. 13

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 PO

Magnetosomes mtbphoto.html mtbphoto.html “Membrane”- coated pieces of magnetite, assist bacteria in moving to microaerophilic environments. An organelle? North is down. Magnetospirillum magnetotacticum 15