1Bacterial Cell Structure (continued)
You are here.
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