1Bacterial Cell Structure (continued)

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2Gram negative cell wall

3Outer 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

4Structure of LPS

www.med.sc.edu:85/fox/ cell_envelope.htm

extends from cell surface.

contains odd sugars e.g. KDO.

Gln-P and fatty acids take the place of phospholipids.

5Periplasmic Space

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

6Periplasm

• 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

7Glycocalyx: capsules and slime layers

www.activatedsludge.info/ resources/visbulk.asp

capsule cell

“Sugar covering”: capsules are firmly attached, slime layers are loose.

Multiple advantages to cells:prevent dehydrationabsorb nutrientsprotection from predators, WBCsprotection 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

8Fimbriae and pili

www.ncl.ac.uk/dental/oralbiol/ 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”).

9Fimbriae and pili-2

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

10Flagella

www.ai.mit.edu/people/ tk/ce/flagella-s.gif www.bmb.leeds.ac.uk/.../icu8/ 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.

11Flagellar structures

img.sparknotes.com/.../monera/ gifs/flagella.gif

www.scu.edu/SCU/Departments/ BIOL/Flagella.jpg

12Runs and Tumbles: bacteria find their way

http://www.bgu.ac.il/~aflaloc/bioca/motil1.gif

13Motility 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.

14Axial 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

15Gliding 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, andcan reverse directions.

http://cmgm.stanford.edu/devbio/kaiserlab/about_myxo/about_myxococcus.html

16From 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.

17Inclusions 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

18Magnetosomes

www.calpoly.edu/~rfrankel/ mtbphoto.html

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

Membrane coated pieces of magnetite, assist bacteria in moving to microaerophilic environments. An organelle?North is down.

Magnetospirillum magnetotacticum