Chapter 4
Part 2.General microbiology
Chapter 1. Morphology, microbial structure and
classificationCompare and contrast the overall cell structure of
prokaryotes and eukaryotes.1Prokaryotic and Eukaryotic Cells
ProkaryoteOne circular chromosome, not in a membraneNo
histonesNo organelles (bo quan)Peptidoglycan cell walls if
BacteriaPseudomurein cell walls if ArchaeaBinary fission (nhn
i)Eukaryote Paired chromosomes, in Polysanuclear membrane Histones
OrganellesPolysaccharide cell wallsMitotic spindle (nguyn phn)
Pseudopeptidoglycan(also known aspseudomurein[1]) is a majorcell
wallcomponent of somearchaeathat differs
frombacterialpeptidoglycanin chemical structure, but resembles
eubacterial peptidoglycan in morphology, function, and physical
structure. The basic components
areN-acetylglucosamineandN-acetyltalosaminuronic acid(peptidoglycan
hasN-acetylmuramic acidinstead), which are linked by
-1,3-glycosidic bonds.Lysozyme, a host defense mechanism, is
ineffective against organisms with pseudopeptidoglycan cell walls.
Lysozyme can break -1,4-glycosidic bonds to degrade peptidoglycan;
however, pseudopeptidoglycan has -1,3-glycosidic bonds, rendering
lysozyme useless.Prokaryote(vi khun nhn nguyn thy)Bacteria
(?)Actinomycetes (x khun)Cyanobacteria (vi khun lam, to lam)Nhm vi
khun nguyn thy (?)Eukaryote
Yeast Fungi Recognize: morphology, size What is the main feature
that distinguishes prokaryotes from eukaryotes? Figure 4.7a
Prokaryotic Cells: ShapesAverage size: 0.2 1.0 m 2 8 mMost
bacteria are monomorphic (the same shape)A few are pleomorphic
Identify the three basic shapes of bacteriaFigures 4.1a, 4.2a,
4.2d, 4.4a, 4.4b, 4.4c
Basic ShapesBacillus (rod-shaped) (trc khun)Coccus
(spherical)SpiralSpirillum (xon khun) Vibrio(phy khun)Spirochete
(xon th)
ArrangementsPairs: Diplococci, diplobacilli
Clusters: Staphylococci
Chains: Streptococci, streptobacilliHow would you be able to
identify streptococci through a microscope?
Staphylococcus aureusEnterococcus faecalis
Bacillus megateriumRhodospirillum rubrum
Vibrio cholerae
Unusually Shaped Bacteria
Unusually Shaped BacteriaStructures External to the Cell
WallDescribe the structure and function of the
glycocalyx.Differentiate flagella, axial filaments, fimbriae, and
pili.Describe the structure and function of the
glycocalyx.Differentiate flagella, axial filaments, fimbriae, and
pili.
The Structure of a Prokaryotic Cell
Tin maoKhun maoTh nhnMng nhyMng t boThnh t noDefine:
composition, structure, roleFlagella and Fimbria /pilus (tin mao,
khun maoCapsule (mng nhy)Cell wal {note: G(-) and G(+)}Cytoplasmic
membrane (mng t bo cht) Cytoplasm (t bo cht)Nuclear body (th
nhn)PlasmidRibosomeVacuole (khng bo)Inclusion (ht d tr)Spore,
endospore (bo t)
FlagellaOutside cell wallMade of chains of flagellinAttached to
a protein hookAnchored to the wall and membrane by the basal
bodyThe Structure of a Prokaryotic Flagellum
Arrangements of Bacterial FlagellaMotile CellsRotate flagella to
run or tumbleMove toward or away from stimuli (taxis)
Motile Cells
Axial FilamentsAlso called endoflagellaIn spirochetesAnchored at
one end of a cellRotation causes cell to move
A Diagram of Axial Filaments
Fimbriae and PiliFimbriae allow attachmentFimbriae and PiliPili
Facilitate transfer of DNA from one cell to anotherGliding
motilityTwitching motility
Why are bacterial capsules medically important?How do bacteria
move?{Fimbriaeandpiliare interchangeable terms used to designate
short, hair-like structures on the surfaces of procaryotic cells.
Like flagella, they are composed of protein. Fimbriae are shorter
and stiffer than flagella, and slightly smaller in diameter.
Generally, fimbriae have nothing to do with bacterial movement}
Outside cell wallUsually stickyCapsule: neatly organizedSlime
layer: unorganized and loose Extracellular polysaccharide allows
cell to attachCapsules prevent phagocytosis (Thc bo)
The Cell WallPrevents osmotic lysisMade of peptidoglycan (in
bacteria)
PeptidoglycanPolymer of disaccharide:N-acetylglucosamine (NAG)
N-acetylmuramic acid (NAM)
Peptidoglycan in Gram-Positive BacteriaLinked by
polypeptidesGram-Positive Bacterial Cell Wall
Gram-Negative Bacterial Cell Wall
Thick peptidoglycanTeichoic acidsGram-positiveCell Wall
Thin peptidoglycanOuter membranePeriplasmic
spaceGram-positiveCell Wall
Gram-Positive Cell WallsTeichoic acidsLipoteichoic acid links to
plasma membraneWall teichoic acid links to peptidoglycanMay
regulate movement of cationsPolysaccharides provide antigenic
variation
Gram-Negative Cell Wall
Gram-Negative Outer MembraneLipopolysaccharides, lipoproteins,
phospholipidsForms the periplasm between the outer membrane and the
plasma membraneGram-Negative Outer MembraneProtection from
phagocytes, complement, and antibioticsO polysaccharide antigen,
e.g., E. coli O157:H7Lipid A is an endotoxinPorins (proteins) form
channels through membraneThe Gram Stain
Gram-Positive(b) Gram-Negative
The Gram Stain MechanismCrystal violet-iodine crystals form in
cellGram-positiveAlcohol dehydrates peptidoglycanCV-I crystals do
not leaveGram-negativeAlcohol dissolves outer membrane and leaves
holes in peptidoglycanCV-I washes outFigure 3.12b
Micrograph of Gram-Stained Bacteria462-ring basal bodyDisrupted
by lysozymePenicillin sensitiveGram-PositiveCell Wall
4-ring basal bodyEndotoxinTetracycline
sensitiveGram-NegativeCell Wall
Atypical Cell WallsAcid-fast cell wallsLike gram-positiveWaxy
lipid (mycolic acid) bound to
peptidoglycanMycobacteriumNocardiaAtypical Cell
WallsMycoplasmasLack cell wallsSterols in plasma
membraneArchaeaWall-less orWalls of pseudomurein (lack NAM and
D-amino acids)Damage to the Cell WallLysozyme digests disaccharide
in peptidoglycanPenicillin inhibits peptide bridges in
peptidoglycanProtoplast is a wall-less cellSpheroplast is a
wall-less gram-positive cellProtoplasts and spheroplasts are
susceptible to osmotic lysisL forms are wall-less cells that swell
into irregular shapes Why are drugs that target cell wall synthesis
useful?Why are mycoplasmas resistant to antibiotics that interfere
with cell wall synthesis?Structures Internal to the Cell
WallDescribe the structure, chemistry, and functions of the
prokaryotic plasma membrane.Define simple diffusion, facilitated
diffusion, osmosis, active transport, and group
translocation.Identify the functions of the nucleoid and
ribosomes.Identify the functions of four inclusions.Describe the
functions of endospores, sporulation, and endospore
germination.
The Plasma Membrane
The Plasma MembranePhospholipid bilayerPeripheral
proteinsIntegral proteinsTransmembraneProteins
Fluid Mosaic ModelMembrane is as viscous as olive oilProteins
move to functionPhospholipids rotate and move laterallyThe Plasma
MembraneSelective permeability allows passage of some
moleculesEnzymes for ATP productionPhotosynthetic pigments on
foldings called chromatophores or thylakoids
ChromatophoresThe Plasma MembraneDamage to the membrane by
alcohols, quaternary ammonium (detergents), and polymyxin
antibiotics causes leakage of cell contents
Movement of Materials across MembranesSimple diffusion: Movement
of a solute from an area of high concentration to an area of low
concentration
Movement of Materials across MembranesFacilitated diffusion:
Solute combines with a transporter protein in the membraneMovement
of Materials across Membranes
Movement of Materials across MembranesOsmosis: The movement of
water across a selectively permeable membrane from an area of high
water to an area of lower water concentrationOsmotic pressure: The
pressure needed to stop the movement of water across the
membrane
Movement of Materials across MembranesThrough lipid
layerAquaporins (water channels)
The Principle of Osmosis
The Principle of OsmosisMovement of Materials across
MembranesActive transport: Requires a transporter protein and
ATPGroup translocation: Requires a transporter protein and PEPWhich
agents can cause injury to the bacterial plasma membrane?How are
simple diffusion and facilitated diffusion similar? How are they
different?
CytoplasmThe substance inside the plasma membrane
The NucleoidBacterial chromosome
Ribosomes
The Prokaryotic RibosomeProtein synthesis70S50S + 30S
subunits
MagnetosomesInclusionsMetachromatic granules
(volutin)Polysaccharide granulesLipid inclusionsSulfur
granulesCarboxysomes
Gas vacuolesMagnetosomesPhosphate reserves
Energy reservesEnergy reservesEnergy reservesRibulose
1,5-diphosphate carboxylase for CO2 fixationProtein-covered
cylindersIron oxide (destroys H2O2)EndosporesResting cellsResistant
to desiccation, heat, chemicalsBacillus, ClostridiumSporulation:
Endospore formationGermination: Return to vegetative state
Endospores
Formation of Endospores by SporulationWhere is the DNA located
in a prokaryotic cell?What is the general function of
inclusions?Under what conditions do endospores form? S sinh sn ca
vi khun
