1Bacterial Cell Structure (continued)

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2Peptidoglycan structure•Bacteria typically face hypotonic environments•Peptidoglycan provides support, Limits expansion of cell membrane•Bacteria need other protection from hypertonic situations

3Gram negative cell wall

4Outer membrane

• Lipid bilayer membrane– Inner and outer leaflets

• Inner leaflet made of phospholipids; outer leaflet is made of lipopolysaccharide (LPS)

• LPS = endotoxin– Proteins for transport of substances

• Porins: transmembrane proteins– Barrier to diffusion of various substances

• Lipoprotein: anchors outer membrane to PG

5Structure of LPS

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

extends from cell surface.

contains odd sugarse.g. KDO.

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

6Periplasmic Space

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

7Periplasmic space:

• A lot like cytoplasm, with– Peptidoglycan layer– Proteins that aid in transport– Proteins that break down molecules– Proteins that help in synthesis.

8Glycocalyx: 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

9Fimbriae 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”).

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.

11Prokaryotic vs. eukaryotic flagella

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

Prokaryotic flagella:

•Made of protein subunits

•Protrude through cell wall and cell membrane.

•Stiff, twirl like a propeller

Eukaryotic flagella:

•A bundle (9+2) of microtubules (made of protein)

•Covered by cell membrane

•Whipping action

12Chemotaxis• Bacteria change how they move in

response to chemicals• Bacteria move toward attractants

(e.g. nutrients).• Bacteria move away from

repellants.• In this figure, bacteria use up

nutrients in the agar, then move outward to where more nutrients are, producing rings of growth.

http://class.fst.ohio-state.edu/fst636/SP2004_mustafa/chemotaxis%20demo_SP04.htm

13Runs and Tumbles: bacteria find their way

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

14Spirochetes have internal flagella

• Axial filament: a bundle of internal flagella– Between cell membrane and outer membrane

in spirochetes– Filament rotates, bacterium corkscrews

through mediumSome bacteria move without flagella• Gliding

– No visible structures, requires solid surface– Slime usually involved.

15Axial 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

16Gliding 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.

www.microbiology.med.umn.edu/ myxobacteria/trails.jpg

17From 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.

18Inclusions 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

www.qub.ac.uk/envres/EarthAirWater/ phosphate_removal.htm

19Magnetosomes

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

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

Magnetospirillum magnetotacticum

20How things get in (and out) of cells• Eukaryotic cells

– Have transport proteins in membrane– Have a cytoskeleton made of microtubules

• Allows for receptor mediated endocytosis, phagotcytosis, etc.• Cell membrane pinches in, creates vesicle

• Prokaryotic cells– Have very little cytoskeleton– Can NOT carry out endocytosis– Entry of materials into cell by diffusion or transport

processes ONLY.

21Illustrations: entry into cells

http://bio.winona.msus.edu/bates/genbio/images/endocytosis.gifhttp://www.gla.ac.uk/~jmb17n/Teaching/JHteaching/Endocytosis/figures/howdo.jpg

Both prokaryotes and eukaryotes.

Only eukaryotes.

22How molecules get through the membrane

Small molecules like gases can diffuse through the bilayer.

Larger or more hydrophilic molecules require transport proteins.

Active transport requires metabolic energy.

23Review of eukaryotic cells

Mitochondrion Plasmalemma (cell membrane)nucleus, ribosomeslysozomeendoplasmic reticulumgolgi body

www.steve.gb.com/ science/cell_biology.html