PROKARYOTIC ANATOMY: CAPSULES, FLAGELLA, PILI
6/30/83, rvsd 8 July 1995, 25 June 99, 13 July 01, 7 July 03, 14 July 04, 11 July 05, 5 Apr 06, 9 July 07
TFC, 7th p 77-99, Alcamo, p. 87-, Atlas, pp 111-139, TFC, 8th p 76-96, Black 6th: 77-89, Bauman 2nd, 55-65
CELL SHAPE (2): coccus, bacillus, spirillum, pleomorphic
ARRANGEMENT: depends on how cells stick together after mitosis:
diplo, strepto-, tetrad, sarcinae, staphylo-
GLYCOCALYX (sugar + cup, flower) sticky, gelatinous layer, shown by negative stain. (Not in spirillum)
capsule if firmly attached to bacterial cell (see p 61)
slime layer so called if loose, unorganized
Extracellular Polymeric Substance = EPS, if composed of sugars: used for attachment especially
mucopolysaccharide: polysaccharide [dextran] cross-linked with small peptides
Function: buffers, protects fr phagocytosis, dehydration, adheres organism to substrate
pathogenicity: B. anthracis + S. pneumoniae only pathogenic if encapsulated (smooth)
adherence: Klebsiella sticks to respiratory tract, S. mutans in forming dental caries.
“Ropy” milk, beer due to Alcaligenes viscolactis capsular material, ropy bread to B subtilis
Quellung reaction (swelling): swelling of capsule from specific antibody attack, used to type strains
FLAGELLA: (p 62) element of motility, spins to move. Flagella cannot be seen unless coated with dye.
filament is a polymer of flagellin (H antigen), hook at proximal end, attached via basal body to bacterium:
Gm pos: single pair of rings in basal body
Gm neg: two pairs of rings in basal body, inner ring rotates, outer is stator Example:
Styles of flagellar arrangement (more)(p63)
peritrichous “around hairs” E. coli, etc
monotrichous (single polar flagellum) Vibrio
lophotrichous [tuft hair] (2 flagellae or more at l end) Pseudomonas
amphitrichous (tufts of flagellae at both ends) Spirillum
permit chemotaxis attractant: steady runs, repellant: runs with many tumbles.
AXIAL FILAMENTS: (p 63) in spirochetes, cell wraps around axial filament
move by boring or snake-like movement (Treponema & Leptospira)
MOVEMENTS: (p 64) Run: clockwise rotation, 1 second (favorable conditions)
Tumble: counterclockwise, 0.1 sec. (Unfavorable conds.)
PILI: [hair] (p 65) hollow structures of subunits pilin [antigenic]
1) fimbriae aid in attachment to substrate, enhance pathogenicity, eg: Neisseria gonorrhoeae
pellicle: fuzzy ort shiny layer on top of air-water interface by aerobic bacteria
2) sex pili aid in transfer of DNA
PROKARYOTIC ANATOMY II: CELL WALLS, PLASMA MEMBRANE, ENDOSPORES
6/30/83, rvsd 8 July 1995, 25 June 99, 13 July 01, 7 July 03, 14 July 04, 11 July 05, 13 July 05, 5 apr 06, 9 July 07
TFC, 7th p 77-99, Alcamo, p. 87-, Atlas, pp 111-139, TFC, 8th p 76-96, Black 6th: 90-95, Bauman 2nd,65-92
CELL WALL: (p 66)
20x norm pressure inside (300 psi!), cell wall hold contents in, gives structure & protection
composed of peptidoglycan (murein), a polysaccharide with alternating NAG-NAM (10 to 65 in row):
glycan: NAG: N acetylglucoseamine (p 66)
cross connected via 1-5 AA (alternating D and L) with peptide cross-linking side chains .
bacteria grouped according to antigenicity of cell wall (example: group A strept.)
Overview: p 68:
Gram positive 25 nm thick of peptidoglycan plus antigenic teichoic acid (p 68) (PO4 + glycerol (or ribitol) or phospholipid)
Gram negative only 3 nm thick wall, plus second membrane on exterior of cell wall with lipopolysaccharide
periplasmic space between membranes: protective enzymes
LIPOPOLYSACCHARIDE (LPS, in outer membrane of Gram negative bacteria) consists of:
Lipid A (p. 68) embedded in outer membrane, released as endotoxin on death. Trigger macrophages to release cytokines: chills, fever, weakness, generalized aches, shock, death.
O polysaccharide projects out, constitutes "O" antigen as in O157:H7 of pathogenic E. coli.
p 68: contrast Gm +/Gm-: As a result of the extra barrier in Gm- bacteria, more resistant to antibiotics, salts and dyes
AGENTS AGAINST CELL WALLS:
Lysozyme (found in tears, etc) cuts polysaccharide
Penicillin inhibits synthesis, leads to protoplast formation in growing cells
Mycoplasma have no cell wall, instead have cholesterol in membrane (a unique group of bacteria)
PLASMA MEMBRANE: (p 69) 60% protein, 40% phospholipid, fluid mosaic model
Mesosomes: invaginations of plasm membrane, form septum. DNA attached here incr absorb
Alcohols, quaternary ammonium compounds and polymyxins damage the plasma membrane
MOVEMENT ACROSS MEMBRANE: (p 71)
Diffusion,
osmosis
(p 73), hypertonic solutions draw water out, cell collapses (plasmolysis)
Facilitated
diffusion, active
transport (p 74) semipermeable
membrane video
CYTOPLASM: Inclusions (stored nutrients), classification of which aid in classification:
volutin: stored poly P04 (red with methylene blue, diagnostic of C.orynebacterium diphtheria)
metachromatic with methylene blue staining (variable staining)
polysaccharide starch or glycogen, iodine shows as black/purple grains
lipid:
poly
β-hydroxybutyric acid,
ENDOSPORES: (p 547) specialized resting cells, survive extreme heat , toxins, chemicals, xeroduric.
Survives 10,000 yr, possibly 25 mil in amber?
Four genera, only Bacillus and Clostridium are pathogenic
Illustrate process of sporulation:(p. 76)
1. spore septum forms by invagination of plasma membrane
2. newly synth DNA surrounded (forespore) by double layer of membrane (spore and cell memb)
3. Cortex of peptidoglycan between two membranes
4. spore coat of protein synthesized on outside.
Layers: 1) spore coat, 2) outer memb, 3) cortex, 4) inner memb, 5) inside: dipicolinic acid, stabilizes DNA
EUCARYOTIC CELLS [Not covered?]
Flagella and cilia
Cell wall
Plasma membrane
Cytoplasm
ORGANELLES: Nucleus, endoplasmic reticulum, golgi complex, mitochondria,
Centrosome and centrioles, chloroplasts, inclusions
