Morphology and Ultrastructure Flashcards
Average size of a bacterium?
1 uM
List a few unique cellular features of Bacteria?
Lack of nucleus and other membranes organelles
DS circular DNA
Smaller Ribosomes (70S)
Plasmids
In gram staining, what colors do positive and negative turn?
Purple = Positive Red = Negative
What two criteria are primarily used for classification?
Size/shape
Gram +/-
What do you do in a gram stain?
Smear, Heat fixation, crystal violet + iodine, wash, safranin
What makes a gram + purple?
Stain gets trapped in the thick, cross-linked peptidoglycan layer.
What stain you yo use for mycobacterium?
Acid-Fast Staining
How (what lab technique) would you use to assess bacterial genetics? When would this be important?
PCR
Esp. Important for slow growing strands
The lack of a bacterial nuclear membrane allows for…
Coupled Transcription and Translation
Location of DNA in the bacterial cell?
the nucleoid and plasmids
Size of two subunits and full ribosome complex?
30S + 50S = 70S
With the exception of myco, what do bacterial cell membranes lack?
Steroids
Three important roles of the bacterial lipid bilayer?
Electron Transport/Energy Production
Pumps present to maintain internal environment
Lined internall with actins that determine shape/division
Describe a G+ cell wall
Thick, multilayered
Mostly Peptidoglycan
Teichoic Acids Make covalent linkages and anchor to membrane
What does lysozyme do to fight bacteria?
Cleaves glycan backbone of peptidoglycan
Death by loss of osmotic control
Are peptidoglycan and techoic acid still present in gram negs?
A little PG
No TA
What parts of PG binds to provide crosslinkage?
D-Ala to Lys
Two repeating subunits in PG?
NAG and N-Acetylmuranic Acid
Importance of the periplasmic space in gram negatives?
Breakdown molecules (proteases, phosphotases, lipases) Many lytic virulence factors
Type ___ virulence factors are a major virulence factor
III
Describe the outer membrane of a gram negative.
Inside normal, outside LPS
LPS is also known as ______. When released it triggers a _______.
Endotoxin
Schwartzman Rxn
What is LPS without its O antigen?
LOS (lipooligosaccharide)
What are the transmembrane proteins called? What gets through them?
Porins.
Materials under 700 Da
Role of lipoproteins in G- bacteria?
Hold outer membrane onto the bacteria
How is LPS crosslinked?
Mg and Ca linkages between phosphates
What is a bacterial capsule?
A loos polysaccharide or protein layer
“Glycocalyx”
Why do we can about bacterial capsules?
Poorly Antigenic
Anti-phagocytotic
Increase Adherance – Biofilms in quorum
What are flagella?
Ropelike cellular propellers made of heavily coiled flagellin.
Driven by ATP motor and chemotactic signals
What are fimbriae?
Hair-like projections outside the cell made of Pilin.
Why do we care about fimbriae?
They increase adherance, and may have specific binding
Also, encompass the F pili
How is mycoplasma an exception to the rule?
Steals host steroids
Role of bactoprenol?
Conveyor belt for precursors to the cell surface
There they can be activated with high energy bonds
Describe the process of peptidoglycan synthesis.
Precursors made in cell
UDP-MurNAC attached to Bactroprenol via UMP release
GlcNAC is added
Translocation to the outside of the cell
Transglycosylases use the pyrophosphate to attach the GlcNAC-MurNAC to the peptidoglycan chain
Bactoprenol is recycled
What antibiotic works by blocking bactoprenol recycling?
Bacitracin
What reaction frovides peptide cross-linkage for developing LPS?
Transpeptidation from 3rd free amino and D alanine in the 4th position of the other peptide
Other name for transpeptidases invovled in LPS formation?
Penicillin-binding proteins
Because targeted by penicillin and other beta lactams
How does vancomycin work?
Blocks D-Ala D-Ala site
Three primary components of LPS?
Lipid A
Core Polysacharide
O Antigen
What is Lipid A? What does it do?
Glucosamine Disacharide Backbone
Endotoxin Activity, FA Anchor in Outer Mem
What is Core polysaccharide?
Branched, 9-12 sugars
2-keto-3-deoxy-octenoate (KDO)
What is an O Antigen?
50-100 sach. units
What is a septum?
A bacterial cross wall generated in the process of cell division
Difference between streptococci and staphylococci cell division?
Strep divid at 180 degrees – Make chains
Staph divide at 90 degrees – form bundles
How are chains/cluters of bacteria formed?
Incomplete clevage.
Spores are ______ gram negative.
NEVER
Describe the protein coat of a spore.
Inner Mem + 2x Peptidoglycan + outer kertain-like protein coat
What is required for a spore to germinate?
H2O and Trigger Nutrients
How do bacteria transfer genes between them?
F Pilus
Shape of vibrio?
Comma
Shape of spirochete?
Spring
Shape of Spirillum?
Lazy S
Shape of Coccus?
Round
How might relatedness of two bacterial strands be assessed?
Biochemical tests of metabolically active
DNA optical mapping
Serotyping
Direct Gene Comparisons (Virochip)
How are DNA optical maps made?
Restriction endonucleases cut DNA at different sequences then maps are made that show the points they come back together
Difference between USA 300 and USA800
300 – community acquired, commonly abx resistant with toxin
800 – Hospital resistant, less significant
What does an H antigen correspond with?
Flagellar Antigens
What does an O antigen correspond with?
Outer Membrane
What does a K antigen correspond with?
Capsule
Cell shape of mycoplasma?
Highly pleomorphic
Why are mycoplasma obligate parasites?
They require cholesterol from eukaryotic cell hosts
What shape do fusiform bacteria maintain?
Spindle
Why do archaea tend to be ignored in medical microbiology?
No known diseases assiciated
How do archaea maintain stability in high temperatures?
Monolayer of lipids instead of a bilayer
How do bacteria usually divide?
Binary fission
Three examples of membrane invaginations?
Mesosomes
Phycobilisomes
Chromatophores
What are cytoplasmic somal bodies?
Storage Organelles
What are inclusion bodies?
Insoluble polymers
What are three types of inclusion bodies?
poly-beta-OH butyrate, starch, glycogen (Carbon)
Sulfur (sink for sulfur oxidizers)
Polyphosphate granules
What are enzymatic reaction centers?
Locations of DNA, RNA, and Protein localization
What are plectonemes?
DNA supercoils that are a part of colocating genes and proteins that work together
How do materials get through the bacterial plasma membrane?
Rocker-Switch Mechanism – External and internal binding sites, bottleneck that is sometimes a selectivity filter
How do bacteria perform endocytosis.
They don’t.
Secretory systems that have a needle complex?
3, 4, 6
How are GlcNAc and MurNAc linked?
beta 1-4 glycocidic bond
As PG breaks down, what activated the immune response?
GlcNAc-MurNAc disaccharide
What is a limit of bacitracin activity?
It will only kill growing cells
How is the LPS core generated?
Added as monosaccharide units to Lipid A on the cytosolic side, then flipped to the outside
Repeat unit is synthesized by cytoplasm, carried to peri by bactoprenol, added to core
transfer to OM by periplasm-bridging proteins
Significance to sialic acid in immune response?
Causes the capsule to mimic self-antigen
Significance of pilin in immune response?
Bacteria can switch pilin when detected by the immune system
Difference between flagella and eukaryotes and prokaryotes?
Euk – Back and Forth
Pro – Propeller
What causes the flagella to spin?
Proton gradient moving through the rotor (Mot A/B proteins)
What is the C ring?
A switch that allows rotation to change direction
CCW – Swim
CW – Tumble
How does chemotaxis work?
Attractant binds to MCP which blocks CHEA activity
CHE A can no longer trigger CHE Y
CHE Y can’t cause tumble
Keep swimming to attractant
Methylation of alpha helix in MCP undoes attractant activity
Significance of S-layers?
Single crystalline protein that surrounds some cells
Molecular Sieve
Protects from complement
