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 Proteins for transport of substances Porins: tri-subunit, transmembrane proteins Barrier to diffusion of various substances Lipoprotein: anchors outer membrane to PG

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

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

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

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

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

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

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.gif www.bmb.leeds.ac.uk/.../icu8/ introduction/bacteria.html

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

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

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.

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

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

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.

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

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.html http://geoweb.tamu.edu/courses/geol101/lab/topo_maps/IMG00006.GIF