113 terms

Chapter 4: Prokaryote (pt 1)

Size of prokaryote
1-10 um
size of eukaryote
10-100 um
size of virus
10-100 nm
Prokaryotes Vs. Eukaryotes
Prokaryotes: -Basic building blocks: same
-Size: smaller
-Nucleus: No
-Chromosomes: Singular, circular, no histones
-Cytoskeleton: No
-Membrane enclosed organelles: No
-Ribosomes: Smaller
-Flagella: Simple
-Cell wall: complex (peptidoglycan)
-Cell Division: Binary fission
Eukaryotes: -Basic building blocks: same
-Size: larger (-10x)
-Nucleus: Yes
-Chromosomes: Multiple, linear, histones
-Cytoskeleton: Yes
-Membrane enclosed organelles: Yes
-Ribosomes: Larger
-Flagella: Complex
-Cell wall: Simple
-Cell division: mitosis
Cocci (bacterial shapes)
-Arrangements can help in identification
Tetrads (cocci)
-divide two planes and remain in cluster of 4
Sarcinae (cocci)
-cluster of 8 (4 on bottom, 4 on top)
grape-like clusters
Bacilli (bacterial shapes)
-Little staffs or rods
-bacillus refers to shape (italicized bacillus refers to genus)
-only divide vertically
-may be singles
Diplobacilli (bacilli)
set of 2 bacilli
Streptobacilli (bacilli)
chains of bacilli
-more ovular (like cocci)
-hard to distinguish
-short, stumpy rods
Spiral (bacterial shapes)
-Spirochetes- axial filament for movement
-axial filament= endo flagella
-2 organisms: Treponema pallidium
Barellia burgdorferi
-Most cells monomorphic
Vibrios (spiral)
-curve rods (comma shaped)
-Vibrio cholera of cholera
Vibrio cholera
-causes Cholera
-rice water diarhea
Spirillum (spiral)
-rigid corkscrews with whip-like tail
-spirilla= plural
-usually have multiple flagella
-corkscrew but are flexible and have a special axial filament for movement
axial filament (spirochetes)
-endo flagella
-wraps around the cell
-between membrane and sheath
-corkscrew movement through water
-anchored at one end of a cell beneath and outer sheath
Treponema pallidium
-causes: syphillis
Barellia burgdorferi
causes: lyme disease
Monomorphic (spirochetes)
-most cells
-1 normal shape
-age could affect
Pleomorphic (spirochetes)
-can appear in several shapes
Bacterial surface stuctures
-all 3 composed of proteins
-shorter, more numerous
-probably for adhesion to animal tissues (pathogen) or biofilms
-attaches cell to surfaces
-longer and only a few
-bacterial conjugation or attachment to tissue in some pathogens
-act as syringe
-only has one or two
-important for diseases
-transport materical to another cells
-infect cells, inject proteins into host cells. proteins direct cell to rearrange cytoskeleton and form a pedestal
Microbial locamotion
-intentional motion: bacterium going towards stimulus
-Many bacterial cells able to move
-require energy (ATP)
-Different types of motion/structures:
-Majority have flagella (flagellum)
-Axial filament
-May glide (might involve pili)
-May float with gas vesicles
-Brownian motion: vibrations
-Streaming: floating with water (NOT locamotion)
Why be motile?
-get to or move away from stimuli
-move in response to taxes
-other taxes
movement in response to stimuli
-response to chemicals (usually addressed in regards to swimming bacteria)
-food, nutrients, toxins (chemicals)
response to light
Other taxes
-other conditions
Types of Flagella
-Long thing appendages
-protein subunits in helical arrangement
-arrangement indicative of cetrain organisms (ie: e.coli= peritrichous)
Peritrichous (flagella)
all around cell
-one flagella
-several flagella on one end
-both ends
no flagella
Flagella structure
-3 main parts: basal body, hook, and filament
-hook allows for more movement of water
-flagella rotate around the hook (no whip-like motion like eukaryotes
Flagella movement
-organism sense chemicals
-flagella turned on to move in certain direction
-short distances
Run (flagella movement)
- all flagella go to one end of cell and rotate in one direction
Tumble (flagella movement)
-throws bacteria spin
-bacterium reaccesses situation
-changes direction of movement of flagella
Prokaryote vs. Eukaryote (flagella)
Prokaryote: -Size: 10x smaller
-Number: multiple
-Movement: circles
-Location: attached to cell wall and plasma membrane
Eukaryote: -Size: 10x larger
-Number: one or a few
-Movement: whip-like motion
-Location: inside the plasma membrane
The Glycocalyx
-polysaccharide (may have some aa) around many prokaryotes
-slime layer
Capsule (glycocalyx)
-excludes india ink
Slime layer (glycocalyx)
-easily deformed
-more difficult to see
Roles of Glycocalyx
-attachment of pathogenic organisms to host
-immune system evasion
-protection vs. desiccation
-example: Strep. pneumoniae
-important in disease:
-attach to things
-protect organisms from phagocytosis
white blood cell eats bacteria and destroys it
Streptococcus pneumonia
-causes: typical pneumonia
-capsule (pathogen)
-no capsule: not a pathogen
Cell envelope
- cell wall + cell membrane
-cell wall- peptidoglycan
-Complex polysaccharide layer outside of cell membrane
-Additional complexities and outer membrane if Gram negative
-more complex than eukaryote
-Cell membrane
-lipid bilayer inside cell wall
Bacterial cell walls
-Don't have cytoskeleton
-responsible for cell shape
-prevent cell from rupturing due to internal water pressure
-semi-rigid (more flexible in prokaryotes)
-Complex makeup
-peptidoglycan (not in Archaea)
Gram + vs. Gram - Cell walls
-membrane= phospholipid bilayer
-gram +: -thick layer of peptidoglycan
-teichoic acids imbedded inside peptidoglycan
-gram -: -thin layer of peptidoglycan
-no teichoic acids
-outer membrane (surrounds peptidoglycan)
Gram + (cell wall)
-thick layer of peptidoglycan
-teichoic acids imbedded inside peptidoglycan
Gram - (cell wall)
-thin layer of peptidoglycan
-no teichoic acids
-outer membrane (surrounds peptidoglycan)
Pariplasm (gram - cell wall)
liquid in space between membranes
Pariplasmic spaces (gram - cell wall)
space between two membranes
What is peptidoglycan?
-a chain of N-acetylglucosamine (NAG, G) and N-acetylmuramic acid (NAM, M) linked by a glycolytic bond
-always NAG then NAM
-long chains of nag/nam
Glycolytic bond
bond between NAG and NAM
Building peptidoglycan- molecular level
-peptides + sugars
-peptide bridge: connects NAM
-wrap sheet around cell
Peptide bridge
connects NAM
Gram-positive cell walls: Teichoic acids and lipoteichoic acid
-teichochic acids are acidic polysaccharide chains
-strong neg charge
-2 classes: wall teichoic acids and lipoteichoic acids
Wall teichoic acids (gram + cell wall)
-imbedded in wall
lipoteichoic acids (gram + cell wall)
-go through wall
-anchored into cell membrane
-bottom is lipid
Gram-negative cell wall
-phospholipid bilayer
Porin (gram-neg cell wall)
pipe for H20 to flow in/out of cell
Lipopolysaccharide (gram neg cell wall)
-lipid at the bottom
-hexagons are polysaccharides (sugars)
Outer membrane (gram - cell wall)
-lipopolysaccharides (LPS) and polysaccharides
-strong negative charge
-protects against phagocytosis and some antibiotics
-3 Parts
-Lipid A, Core, and O-specific
Lipid A (part of outer membrane) (LPS)
-contains the lipids, the main problem in gram negative infections (endotoxin)
-in membrane
-attached to polysaccharide
-drop in blood pressure (may lead to shock)
Core polysaccharide (part of outer membrane) (LPS)
-same sugars in all LPS
O-specific polysaccharide (part of outer membrane) (LPS)
-different sugars/ repeated differently
lipids are part of outer membrane
proteins that are intentionally secreted
The Gram Stain
-Developed in 1884 by Hans Christian Gram
-He was trying to find a stain to differentiate bacterial cells from eukaryotic nuclei
-Instead found way to differentiate Gram + cells from Gram - cells
-Turned out to be a very useful stain
-Entire diagnosis and treatement regimes are sometimes made based on gram stain results
-gram and shape (ie: gram - cocci)
Gram staining (process)
Step 1) Pimary stain: Crystal violet
-cells purple
-both cells affix dye
Step 2) Mordant: Iodine
-gram pos: dye crystals trapped in wall (CVI2)
-gram neg: no effect of iodine (CVI2)
Step 3) Decolorizing: Alcohol (acetone)
-gram pos: crystals remain in cell wall. cell dehydrated, smaller space, CVI2 gets stuck in cell
-gram neg: outermembrane weakened, wall loses dye. CVI2 leaks out. ends up clears
Step 4) Counterstain: safranin
-gram pos: red dye has no effect.
-gram neg: red dye stains colorless cell
Is the cell wall a good antimicrobial target?
-Yes, the cell wall is unique to bacteria.
-What if you destroy the peptidoglycan? Cell can burst
-The enzyme lysozyme can break-down peptidoglycan between the G ad M (NAG and NAM)
-Many animals secrete lysozyme (saliva, tears, etc.)-
-Found in saliva and tears (makes sense= to fight off bacterial infections)
-Weakens cell wall= water can get in
-If enough gets in, cell swells and bursts= lysis
-selective toxicity
-kill harmful organisms, don't kill good bacteria, don't kill host
How does Penicillin work?
-penicillin targets aa cross bridge (breaks bridges)
Would penicillin be effective against archaea?
-No peptidoglycan
Would penicillin be effective against gram +?
-plenty of peptidoglycan
Would penicillin be effective against gram -?
-No (yes with other drugs)
-LPS has strong neg. charge
-penicillin doesn't get through it
Not all cells stain well
-For those strains that do stain, cell cultures should be young, 16-25 hours old are best
- >24-36 hours: gram + looks gram - (gram variable
-mycoplasma- no cell wall
-mycobacterium- acid-fast cell wall
Cells won't stain if:
1) Cells are too old, some Gram-positive cultures will appear gram-negative (especially those in Bacillus and Clostridium genera) and may be called gram variable
2) Some bacteria do not have cell walls, such as those in Mycoplasm genera
3) Archaea do not have normal peptidoglycan, so they do not stain normally. Their cell walls are composed of polysaccharides and proteins. They do have a component similar to peptidoglycan, but it is different. (purple)
4)-Organisms in the genera Mycobacterium and Nocardium
-cells may stain Gram-positive
-Cell walls contain unique lipids and even alcohols
-Cell walls contain mycolic acids
gram variable
cells that are too old, will apparead gram neg even if they're gram pos
Mycolic Acids
-thick and waxy lipid that makes staining more complex
-makes organism pathogenic
-cell wall resistant to stain
-wax doesn't adhere dye
Acid-Fast Stain
-attaches to waxy layers
-Step 1: Primary stain (stain w/ heat): Carbolfuchsin
-acid- fast: red
-non acid-fast: red
-Step 2: Decolorizing: acid alcohol
-acid fast: red
-non acid fast: colorless
-Step 3: Counterstain: Methylene blue
-acid fast: red (mycobacteria)
-non acid fast: blue (all other bacteria)
Cell membrane
-Inside the cell wall
-Phospholipid bilayer
-Integral membrane proteins
-Permeability barrier, selective (some things enter, leave, excluded)
-Protein anchor
-Site of ATP synthesis (electron transport chain)
-Target for some antimicrobials
Integral protein (cell membrane)
-used to transfer molecules
-movement (flagella)
Moving across the membrane
-passive process = no ATP for energy
Simple Diffusion (passive transport)
-Random movement of molecules from an area of higher concentration to an area of lower concentration
-oxygen and crabon dioxide movement
Facilitated diffusion (passive transport)
-Transporter protein in membrane helps move substance across membrane
-nonspecific: particles can be dissolved in water (ions)
-specific: molecule enters, protein changes shape, molecule shoots out other side
-small molecules (sugars)
-Net movement of solvent molecules across a selectively permeable membrane from and area with high concentration of solvent molecules to an area of low concentration of solvent molecules= Diffusion of water (solvent) across plasma membrane
-water molecules move from an area of low solute concentration to area of high solute concentration
water tunnels that allow water to enter/exit cell
anything dissolved in solvent
what does dissolving (water)
-equal amounts of solute and solvent on both sides of the plasma membrane
-ex: most body fluids, including blood
-higher conentration of solute inside the cell causes cell to swell and burst due to an intake of water (lysis)
-higher concentration of solute outside the cell causes cell to shrink due to loss of water (plasmolysis)
What about active processes?
-Active transport
-diffusion is passive and very slow and may never reach high concentration
-Transport is essential to get anything across an concentration gradient or for cricial items
-Uses energy in the form of ATP
Group Translocation (active process)
-special prokaryotic transport mechanism that alters the substance as it crosses the membrane
-Does not use ATP, but other high energy phosphate compounds
Ex: glucose. too much in cell, wants to leave. glucose changed (phosphorylated). now neg. charge and can't get out
-large molecules?
-In prokaryotes, large molecules usually are transported through translocases (transport proteins in the cell membrane)
-part of secretory system: sometime specific, other systems more general
-Requires energy
-Protein export key because many bacterial enzymes work outside of the bacterial cell
-Ex: Amalyse (starch) or cellulase (cellulose) which cleave starch or cellulose outside the cell in their environment
Cytoplasm (inside bacterial cell)
-Liquid medium inside the cell
-80% water + proteins (enzymes), carbohydrates, lipids, ions
-no cytoskeleton
Nuclear material (inside bacterial cell)
-One circular bacterial chromosome associated with plasma membrane
-May also have circular plasmids that replicates separately from chromosome and may carry genes associated with antibiotic resistance and/or virulance
Bacterial chromosome (nuc. material)
-attached to membrane
conatin genes for proteins that are resistant to antibiotics
Ribosomes (inside bacterial cell)
-sites of protein synthesis, bacterial ribosomes different than eukaryotic ribosomes (good target for antibacterial drugs. ex: streptomycin, erythromycin, etc.)
-make drugs that target bacerial ribosomes, not eukaryotes
Prokaryote vs. Eukaryote (ribosomes)
-Prokaryote: -Size: smaller
-Subunits: 30S + 50S= 70S
-Composition: proteins
-Eukaryotes: -Size: larger
-Subunits: 40S + 50S = 80S
-Composition: proteins and RNA
Sedimentation (S)
-how quickly something falls out of solvent
Unclusions/granules (inside bacterial cell)
-nutrients can accumulate tobe used later as an energy source, such as glycogen and starch polymers
-Only produced by some bacteria, best studied in Bacillus and Clostridium genera
-form within cells during sporulation
-form when growth ceases (nutrient exhaustion)= SURVIVAL
-resistant to heat, chemicals, desiccation, radiation
-allows cell to be dormant for many years
-discovered during studies of sterilization methods
-may involve 200 genes for cellular differentiation
-Stucture= more complex than vegitative
-Layering from inside out: special core wall, then cortex of peptidoglycan, spore coat of spore-specific proteins, exosporium protein covering
-Step 1:spore septum begins to isolate newly replicated DNA and a small portion of cytoplasm
-Step 2: Plasma membrane starts to surround DNA, cytoplasm, and membrane
-Step 3: spore septum surrounds isolated portion, forming forespore (2 membranes)
-Step 4: Peptidoglycan layer forms between membranes
-Step 5: Spore coat (proteins)
-Step 6- endospore freed from cell
reverse process of sporulation
Endospore staining
-Endospores are resistant to normal staining procedures (resistan to chemicals)
-Endospore stain uses heat or chemicals to force stain into endospore
-endospore- green
-vegitative cell- red
-autoclave: uses steam (121*C) and pressure (15 psi); pressure delivers steam to cell