Download Topic 17

Biology 1309
Prokaryotes
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Topics
Topics
– Characteristics (comparison)
– Cell Shapes, Arrangement, and Sizes
– Classification
– Nutrition
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Remember the 3 Domains?
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The Domains:
– Archae
– Bacteria
– Eukaryotes
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Characteristics include
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Ribosomes
Membrane lipids
tRNA
antibiotics
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Comparison (Pro vs. Eu)
• No nuclear membrane
• 0.2-2.0 um
• No membraned
organelles
• Simple flagella, 2
proteins
• Glycocalyx: capsule or
slime layes
• True nucleus
• 10-100 um
• Organelles
(lysosomes, Golgi, ER,
etc)
• Complex flagella,
microtubules
• Possibly in those w/o
cell wall
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Comparison (cont.)
• Complex cell wall (incl. • Simple cell wall, if
peptidoglycan)
present
• Plasma membrane:
• Plasma membrane:
few if any sterols, no
sterols and carbos
carbos
• No cytoskeleton or
• Cytoskeleton, cyto
cyto streaming
streaming
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Comparison (cont...)
• Small Ribosomes- 70S
• DNA: Single, circular,
no histones
• Binary fission
• Recombination: no
meiosis, fragment
transfer only
• Large ribosomes - 80S
+ 70S in organelles
• DNA: Multiple, linear,
w/ histones
• Mitosis
• Recombination:
meiosis
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Bacteria
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No membrane bounded organelles
Peptidoglycans
Antibiotic sensitivity
Binary fission
No Histones
70S ribosome
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The Amazing Flagella:
Three main parts of the flagella include the basal body, hook, and filament.
Details of the basal body in gram negative cell
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Different arrangements of flagella exist for different species.
Some flagella arrangements.
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Prokaryotic Sex!
Pili enable conjugation, the transfer of DNA, from one bacterial cell to another.
Three bacteria in the process of conjugating
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Glycocalyx
• Capsule
– Protects bacteria from immune cells (sticky)
• Slime layer
– Enable attachment and aggregation of bacterial
cells
– loosely bound to the cell
– associated with the formation of biofilms (eg. on teeth)
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The capsule is tightly bound
to the cell, and is associated
with pathogenic bacteria.
Capsule = halo
Center = bacterial cell
Encapsulated bacteria
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Bacterial Cell envelope
• Cell wall
– Gram-positive
– Gram-negative
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Cell wall
• Gram positive cell wall (+ Purple)
– Thick peptidoglycan (PG) layer
– Acidic polysaccharides
– Teichoic acid and lipoteichoic acid
• Gram-negative cell wall (- Pink)
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Thin PG layer
Outer membrane
Lipid polysaccharide
Porins
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Classification
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Phenotypic methods (biochemical + staining)
Molecular methods (sequencing)
Taxonomic scheme
Unique groups
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Archaea bacteria
• Associated with extreme environments
• Contain unique cell walls
• Contain unique internal structures
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The Hot Geysers in Yellowstone!
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Archae
• Lack peptidoglycans
• Inhabit extreme environments
– CH4
– Halophiles
– Thermophiles
• No Antibiotic sensitivity (!)
• 70S ribosomes
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Prokaryotic Nutrition
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Nutrition:
Sources of essential nutrients
• Required for metabolism and growth
– Carbon source
– Energy source
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Defined by Carbon Source
• Heterotroph
(depends on other life forms)
– Organic molecules
– Ex. Sugars, proteins, lipids
• Autotroph
(self-feeders)
– Inorganic molecules
– Ex. CO2
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Growth factors
• Essential organic nutrients
• Not synthesized by the microbe, and must be
supplemented
• Ex. Amino acids, vitamins
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Energy Source Types
• Chemoheterotrophs
• Photoautotrophs
• Chemoautotrophs
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Chemoheterotrophs
• Derive both carbon and energy from organic
compounds
– Saprobic
• decomposers of plant litter, animal matter, and dead
microbes
– Parasitic
• Live in or on the body of a host
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Photoautotroph
• Derive their energy from sunlight
• Transform light rays into chemical energy
• Primary producers of organic matter for
heterotrophs
• Primary producers of oxygen
• Ex. Algae, plants, some bacteria
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Chemo organic autotrophs
• Two types
– Chemo organic autotroph
• Derives their energy from organic compounds and their
carbon source from inorganic compounds
– Lithoautotrophs
• Neither sunlight nor organics used, rather it relies
totally on inorganics
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Saprobe mode of action
Extracellular digestion in a saprobe with a cell wall.
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Nutritional categories summary
(based on carbon and energy source)
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4 Transport mechanisms
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Osmosis
Diffusion
Active transport
Endocytosis
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Osmosis
• Diffusion of water
through a permeable
but selective
membrane
• Water moves toward
the higher solute
concentrated areas
– Isotonic
– Hypotonic
– Hypertonic
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Diffusion
• Net molecule movement from
high concentration area to low
concentration area
• No energy is expended
(passive)
• Concentration gradient and
permeability affect movement
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Facilitated diffusion
• Transport of polar
molecules and ions across
the membrane
• No energy is expended
(passive)
• Carrier protein facilitates
the binding and transport
– Specificity
– Saturation
– Competition
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Active transport
• Transport of molecules against a gradient
• Requires energy (active)
• Ex. Permeases and protein pumps transport
sugars, amino acids, organic acids, phosphates
and metal ions.
• Ex. Group translocation transports and
modifies specific sugars
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Endocytosis
• Substances are taken, but are not transported
through the membrane.
• Requires energy (active)
• Common for eucaryotes
• Ex. Phagocytosis, pinocytosis
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