History of MicrobiologyPerson Experiment/Observation Significance
Hooke (1635-1703) Saw molds First microorganism witnessed
van Leeuewenhook (1632-1723)
Saw bacteria Saw bacteria
Cohn (1828-1898) Studied bacteria extensively Founded bacteriology
Pasteur (1822-1895) Experiment: Sterilized broth in flask designed to prevent contaminationResult: No microorganisms grew until contamination introduced
Disproved theory of Spontaneous Generation all life comes from pre-existing life
Koch (1843-1910) Koch’s Postulates:1) Suspected pathogen should be present in all cases
of disease and absent from healthy animals2) Suspected organism should be grown in pure
culture3) Cells from pure culture should cause disease in
healthy animal4) Organism should be isolated and shown to be the
same as the original
Microbial causes of diseaseIdentified pathogens for anthrax, tuberculosis Enrichment culture technique Pure culture
Winogradsky (1856-1953)
Ammonia (NH3) consuming bacteria cannot use sulphur as energy source, vice versaNitrifying bacteria use CO2 as carbon source, NH3 oxidation as energy source
Chemolithotrophy (energy from inorganic compounds) (NH3, H2S)Discovered link between certain bacteria and certain biochemical transformations
Domains of LifeProperty Prokaryotes Eukaryotes
Bacteria Archae
Size 1-5 µm 0.8-100’s µm
rRNA/Ribosomes 70S = 30S + 50S 80S = 40S + 60S
Organelles NO YES –nucleus, mitochondria, chloroplast (plants), Golgi, ER, etc
DNA Circular genomeNucleoid region
Linear chromosomes Membrane Bound nucleus
Transcription/Translation Can occur at the same timeTranscription can be polycistronic
Transcription and Translation separated by nuclear envelope
Endosymbiotic Theory
• Mitochondria and chloroplast have their own circular genome
• Also have 70S ribosomes• This is evidence that organelles were originally
bacteria taken up by a predatory eukaryote ancestor
Endosymbiotic TheoryEukaryotic predatory ancestor
Bacteria
Uptake into cell
DigestionNo Digestion
Begins to produced energy for host, evolving into current mitochondrion
Plasma Membrane
Polar Headgroup
Hydrophobic Tail
MembraneProperty Prokaryotes Eukaryotes
Bacteria ArchaeGram + Gram -
Chemical Links
Ester-linked fatty acids to phosphoglycerol
Ether-linked isoprenes to phosphoglycerol
Ester-linked fatty acids to phosphoglycerol
Strength Enhancers
Hopanoids-Reduce Fluidity, strengthen membrane
Monolayer (glycerol diether) for hyperthermophiles
Sterols –Reduce Fluidity, strengthen membrane
CO
O CO
OC O
Membrane Proteins
Outer Surface Proteins
Inner Surface Proteins Trans-Membrane Proteins
-Bind Substrates in environment (e.g. Chemotaxis)
-Cellular functions in cytoplasm
-Transport molecules through membrane-Can concentrate against gradient
-Process large molecules for transport
-Can be involved in energy yielding reactions
-Can be general or specific for substrates-Uniporters, symporters, antiporters
Cell WallProperty Prokaryotes Eukaryotes
Bacteria Archae
Gram + Gram -
Composition Thick peptidoglycan wall
Thin peptidoglycan wall + lipopolysaccharide layer (core and o-polysaccharides)
Pseudomuein (like peptidoglycan) in methanogens
Only in plants/fungi
Additional Components
Techoic acid Endotoxin (lipid A)
Porins (high permeability)
Bacterial Cell Wall
GRAM + GRAM -
PeptidoglycanTechoic Acid O-
polysaccharide
Core-polysaccharide
Porin Lipoprotein
Endotoxin
LPS
Peptidoglycan and Lysozyme• Peptidoglycan is composed of β(14) linked N-
acetylglycosamine (G) and N-Acetylmuramic acid (M), amino acids (lysine, diaminopimelic acid = DAP)
• Crosslinking = Strength• Lysozyme breaks β(14) bonds-therefore selective for Cell
Wall of Bacteria
-Archae pseudomurein is composed of β(13) linked N-acetylglycosamine and N-Acetylalosaminuronic acid-Lysozyme insensitive
Cell Wall Synthesis
• Divisome complex: Fts proteins for FtsZ ring defining division plane
• FtsI synthesizes peptidoglycan (wall bands show border for new synthesis)
• Glycan pentapeptide precursor must be transported across cell membrane first (Bactoprenol)
Cell Wall Synthesis
M G
G M
M
G
M G
M
M G
FtsI
M G Bactoprenol
Transpeptidation crosslinks glycan layers – inhibited by Penicillin
EndosporesResistance Heat, radiation, drying,
chemicalsExamples Clostridium, Bacillus
High levels of: Ca2+, Dipicolinic acid, small acid soluble proteins
Normal levels of: DNA, ribosomes
Low Levels of: Water, mRNA, macromolecules, enzyme activity, metabolism
Cytoplasmic pH 5.5-6
Cell Mobility
Whooo!
Flagellum
C
MS
P
L
H+
Hook
Flagellin
LPS
Peptidoglycan
Cytoplasm-Powered by proton gradient-Flagellin added to terminus end
Chemotaxis
Cells can either “run” to move or “tumble” to change orientation. Attractants increase frequency of “runs”, repellents increase frequency of “tumbles”
Regulation of Chemotaxis
• 1)Response to signal– Need Membrane Protein to bind
attractant/repellent (MCP = Methyl-accepting Chemotaxis Protein)
– Need to relay the signal to flagellum: CheA which undergoes auto-phosphorylation to CheA-P
– Also CheW involved
Chemotaxis (1)
MCP
Repellent
CheA CheA-P
MCP
Attractant
CheA CheA-P
Speeds auto-phosphorylation
Slows auto-phosphorylation
Regulation of Chemotaxis
• 2)Control of Flagellar Rotation• - CheA-P transfers P to CheY CheY-P causes
flagellar motor to Tumble = no movement (CW rotation)
• CheZ removes P from CheY so that it cannot bind motor CCW rotation = Run
Chemotaxis (2)
MCP
Repellent
CheA CheA-P
CheY-P
MCP
Attractant
CheA CheA-P
Speeds auto-phosphorylation
Slows auto-phosphorylation
CheY
CW spin = Tumble CCW spin = Run
Binds MotorCannot Bind Motor
CheZ
Chemotaxis (3)Even in presence of attractant/repellent it is still desirable to have some random movement
Chemotaxis
• 3) Adaptation (temporally controlled)• -CheR (think regulation) adds methyls to MCP
continuosly • -CheB removes methyls from MCP Becomes
very active when Phosporylated
• Methylated MCP are responsive to Repellents, insensitive to Attractants
Chemotaxis (3)
MCP
Attractant
CheA CheA-P
Slows auto-phosphorylation
CheY
CCW spin = Run
Cannot Bind Motor
CheB (not very active)
CheR Adds Methyls to MCP
Does not slow auto-phosphorylation
CheA CheA-P CheB-P (active)
CheY-P
CW spin = Tumble
Binds Motor
Demethylates MCP for a “reset”
Taxis
• A response to any number of stimuli• Phototaxis (light), aerotaxis (oxygen)• E.coli: Tar aspartate/malate attractants,
Cobalt/Nickel repellents
Molecular Adaptations to Environment
• Hyperthermophiles: Protein Stability– Amino acid substitutions for “heat tolerant folds”:
Maximize ionic forces (between +/-ve charges) of acidic/basic amino acids
-di-inositol phosphate, diglycerol phosphate, mannosylglycerate also produced to stabilize proteins
+ -
Molecular Adaptations to Environment
• Hyperthermophiles: Membrane Stability– Bacteria have membranes enriched with
SATURATED fatty Acids
– Archae can have membrane monolayers (see before)
All single bonds in tails allows for close stacking to Maximize attractive forces
Molecular Adaptations to Environment
• Psychrophiles: Membrane Stability– have membranes enriched with UNSATURATED
fatty Acids
Cis Double Bond in tails causes bend which prevents close stacking increases fluidity
Salt Tolerance
• Halophiles are adapted to high salt concentration– aw = vapour pressure of air in equilibrium with
solution/vapour pressure of air above pure water
– Many ions in solution attract polar water away from its gaseous state in air
Salt Tolerance
• Halophiles are adapted to high salt concentration
Osmotic Pressure Organisms concentrate nutrients, therefore water diffuses into cell
Normal Conditions
High Salt
Osmotic Pressure High Salt concentrations draw water out of cell
What is a cell to do?
Salt Tolerance
• Halophiles are adapted to high salt concentration with COMPATIBLE SOLUTES
High Salt
Osmotic Pressure
Halophiles import/synthesize solutes to return osmotic pressure towards the cytoplasm
“Compatible Solutes” since they do not interfere with cell metabolic reactions (not toxic at high concentrations)
Halophile
Oxygen Tolerance
• Thioglycolate broth (reduces agent gets rid of molecular oxygen)
• Resazurin indicates presence of O2 by turning Pink
Obligate Anaerobe – Can only grow in absence of oxygen
Obligate Aerobe – Can only grow in presence of oxygen
Facultative Aerobe – Can grow in absence of oxygen, but grows better with oxygen
Microaerophilic – Can only grow in presence of low oxygen
Aerotolerant – Unaffected by oxygen content
Oxygen Tolerance
O2 Present-
Oxic Zone
O2 Absent - Anoxic Zone
Obligate Anaerobe
Obligate AerobeFacultative Aerobe
Microaerophilic Aerotolerant
Genetic Regulation
DNA
mRNA
Transcriptional Regulation-positive/negative regulation, riboswitches
Translational Regulation-Attenuation, RNAi
Enzyme Inhibition (allosterics)
Enzyme Inhibition
Allosteric control
Transcriptional Regulation
Negative Control Positive Control-e.g. Maltose catabolism
Inducers bind effector protein Start transcription (catabolic/degradative operons)
Repression-e.g. Arginine synthesisInduction-e.g. Lac operon
Corepressorsbind effector protein Stop transcription (anabolic/biosynthetic operons)
Effector (protein) binds to Operator (DNA sequence)
Activator (protein) binds to Activator Binding Site(DNA sequence)
Transcriptional RegulationNegative Control Positive Control
RNA Polymerase
RNA Polymerase
Repressor protein prevents binding of RNA Polymerase Transcription Blocked
Activator protein promotes binding of RNA Polymerase Transcription Proceeds
Transcriptional RegulationNegative Control - Induction
RNA Polymerase
RNA Polymerase
Repressor protein prevents binding of RNA Polymerase Transcription Blocked
RNA Polymerase
Repressor protein binds inducer, binding of RNA Polymerase allowed Transcription Proceeds
Negative Control - Repression
RNA Polymerase
Co-repressor binds repressor protein, prevents binding of RNA Polymerase Transcription Blocked
Aporepressor cannot bind DNA Transcription Proceeds
Quorum SensingExample: Acyl Homoserine Lactone (AHL)
Cells in population excrete AHL
AHL is taken up by neighbouring cells, binds AHL Activator protein
AHL activator protein promotes transcription
Quorum specific proteins expressed at critical AHL concentration
AHL Synthase expressed produces more AHL
Translational Control
• mRNA is ssRNAcan base pair with itself or bind other molecules
• antisense RNA can base pair with part of mRNA and can block ribosomes from binding
• Riboswitches: RNA can bind small molecules to change mRNA structure free up Ribosome Binding Site for translation
AttenuationTryptophan Operon encodes 5 genes needed to synthesize tryptophan
mRNA
DNA
5 genes
5 internal ribosome binding sites
Attenuation
• Transcription and Translation can occur simultaneously in E.Coli.
• Rho-independent termination of transcription can terminate the mRNA molecule before any of the biosynthetic genes are transcribed
• Signalled by stem-loop in RNA followed by multiple U’s
Attenuation
mRNA
1- codes for trp and can base pair with 2
2- can base pair with 1 or 3
3- can base pair with 2 or 4
4- can base pair with 3Followed by multiple U’s
uuuuu1 2 3 4
Attenuation
mRNA
1- codes for trp and can base pair with 2
2- can base pair with 1 or 3
3- can base pair with 2 or 4
4- can base pair with 3Followed by multiple U’s
uuuuu1
2 3
4
Tryptophan not available in cell Trp genes needed to synthesize more
DNA
RNA polymerase
Ribosome Stalls since it can’t find the tryptophan “1” codes for
2 base pairs with 3
RNA polymerase continues trp genes expressed
Attenuation
mRNA
3- can base pair with 2 or 4
4- can base pair with 3Followed by multiple U’s
uuuuu
1 2 3 4
Tryptophan available in cell Trp genes NOT needed to synthesize any more
DNARibosome continues since it can find the tryptophan “1” codes for, stops at stop codon
3 hybridizes with 4 signals attenuation RNA polymerase
drops off DNA
1- codes for trp and can base pair with 2
2- can base pair with 1 or 3
Practice Questions
• Who was the first person to observe bacteria? Who founded the study of Bacteriology?
a)van Leeuwenhoek/Hookeb)Hooke/Pasteurc)Koch/Cohnd) van Leeuwenhoek/Cohne) Winogradsky/Koch
Practice Questions
• A chemolithoautotroph is an organism which:a) Produces energy from lightb)Oxidizes inorganic compounds for energy, and
uses CO2 as a carbon sourcec) Produces energy from light and uses CO2 as a
carbon sourced) Oxidizes inorganic compounds for energy and
has organic carbon sources
Practice Questions
• A new organism is discovered and is found to have the DNA organized in a discrete region. It is classified as a:
a) Bacteriab) Prokaryotec) Eukaryoted) Archaee) Could be any of the above
Practice Questions
• The E. Coli genome is:a) Circularb) 2.7 million base pairsc) 4.68 million base pairsd) Has multiple Chromosomese) A and C
Practice Questions
• Phototrophsa) Are oxygenicb) Produce energy from Lightc) Utilize Pigmentsd) Can be anoxygenice) B, C, and D
Practice Questions
• Some Bacteria are:a) Responsible for the oxygenation of Earthb) Multicellularc) Protistsd) Obligate intracellular parasites like
Deinococcuse) A and C
Practice Questions
• Methanogens are:a) Euryarchaotab) Archaec) Methane producersd) A, B, and Ce) B and C
Practice Questions
• Which of the following are evidence for the Endosymbiotic Theory
a) Viruses can only reproduce in other cellsb) Endospores are resistant to desiccation and can
survive long periods of timec) Mitochondria and Chloroplasts are related to bacteriad) Cyanobacteria produce oxygen and gain energy from
lighte) None of the above
Practice Questions
• Which of the following statements are true?a) Morphology is a good indicator of physiologyb) Coccus refers to spiral shaped bacteria c) The surface to volume ratio is greater for
smaller organismsd) All Prokaryotes are smaller than Eukaryotese) All of the above are false
Practice Questions
• Which of the following make up the polar headgroup of phospholipids?
a) Fatty acid residuesb) Isoprenec) Glycerold) Phosphate groupse) C and D
Practice Questions
• Membrane Proteins:a) Process large molecules for transportb) Can be embedded in the membranec) Contribute to electron transport reactionsd) Can be peripheral or integrale) All of the above
Practice Questions
• Which of the following are found in bacteria membranes?
a) Sterolsb) Ester-Linked fatty acidsc) Hopanoidsd) Ether-Linked fatty acidse) B and C
Practice Questions
• Which of the following are properties of transport proteins?
a) Can be saturated, and are specificb) Are required for all small, non-polar
moleculesc) Are Regulated by Biosynthesisd) A, Ce)A, B, C
Practice Questions
• Which of the following are found in both Gram positive and negative cell walls?
a) N-acetylmuramic acidb) Techoic acidc) Diaminopimelic acid d) Lysozyme sensitive bondse) A, C, and D
Practice Questions
• The peptidoglycan layera) Makes up 10% of the gram negative cell wallb) Is a major component of archae cell wallsc) Is only found in Gram-positive baceteriad) Contains core, and o-polysaccharidese) Is not found in Staphylococcus aureus
Practice Questions
• The periplasm:a) Is in archae and is composed of pseudomureinb) Has the consistency of gelc) Contains endotoxind) Has very little proteine) None of the above
Practice Questions
• Gas vesicles are composed of 97% _____, and have ____ for crosslinking. Both of these proteins are ____ and allow the vesicles to be water tight and air _________.
a) GvpA, GvpB, hydrophobic, permeableb) GvpC, GvpA, hydrophobic, permeablec) GvpA, GvpC, hydrophilic, permeabled) GvpC, GvpB, hydrophilic, tighte) GvpA, GvpC, hydrophobic, permeable
Practice Questions
• Endospores are high in _____, have very little ______, and can be stained _______.
a) Calcium, acid soluble proteins, with special dyes
b) Dipicolinic acid, mRNA, neverc) Dipicolinic acid, mRNA, with special dyesd) Enzyme activity, ribosomes, normallye) Water, mRNA, with special dyes
Practice Questions
• Which of the following are cell surface structures?
a) Glycocalyxb) magnetosomesc) Sulfur Globulesd) Pilie) A and D
Practice Questions
• Chemical Gradients are senseda) Temporallyb) In Chemotaxisc) By Jedid) In response to lighte) A and B
Practice Questions
• Which of the following are macronutients?a) Cb) Kc) Cad) Nae) All of the above
Practice Questions
• Cell replicationa) Involves Fts proteinsb) Has variable generation timesc) Requires DNA replicationsd) Can have generation times as low as 20
minutese) All of the above
Practice Questions
• If there are 10 cells of an organism with a generation time of 1 hour, how many cells will there be: After 3 hours of logarithmic growth? After 5 hours in stationary phase?
a) 80, 320b) 10, 20c) 30, 50d) 80, 10e) None of the above
Practice Questions
• Which of the following are adaptations to environment?
a) Halophiles synthesizing compatible solutesb) Halophiles developing a monolayer membranec) Thermophiles having membranes with saturated
fatty acidsd) Psychrophiles having membranes with saturated
fatty acidse) A, and C
Practice Questions
• Which of the following stabilizes proteins in thermophiles?
a) Amino acid substitutions to minimize ionic interactions between residues
b) Di-inositol phosphatec) Compatible solutesd) None of a, b, or ce) a, b, and c
Practice Questions
• The internal pH of most acidophilesa) Is greater than 7b) Is around neutralc) Is less than 7d) Can be as high as 9.5
Practice Questions
• Water willa) Flow out in an isotonic environmentb) Will always move into the cell in any
conditionsc) Flow out in a hypotonic environmentd) Flow out in a hypertonic environmente) Combine with LO2 to produce the next
governor general
Practice Questions
• The following shows which type of organism?a) Obligate anaerobeb) Facultative anaerobec) Obligate aerobed) Microaerophilice) None of the above
Practice Questions
• Which is the reaction catalyzed by superoxide dismutase?
a) ATP ADP + Pb) 2 H2O2 2 H2O + O2
c) 4 O2- + 4 H+ 2 H2O + 3 O2
d) 2 O2- + 2 H+ H2O2 + O2
e) All of the above
Practice Questions
• Which of the following are levels of regulation?
a) Enzymeb) Transcriptionc) Transpeptidationd) Translatione) a, b, and d
Practice Questions
• Feedback inhibition acts at the enzyme level of control, by inhibition a(n) _____ enzyme at the ______ of a metabolic pathway.
a) Constitutive/endb) Allosteric/beginningc) Allosteric/middled) Constitutive/beginninge) Allosteric/end
Practice Questions
• DAHP synthases are:a) Involved in glutamic acid degradationb) Isozymesc) Subject to different regulatory controld) Transcriptional control elementse) B and C
Practice Questions
• Negative control:a) Includes the maltose degradation operonb) Includes both the arginine biosynthesis and
lac operonsc) Is a translational level controld) Can be regulated by inducerse) B and D
Practice Questions
• An activator protein:a) Allows the transcription of the lac operonb) Is only active in the presence of an inducerc) Must bind near the promoterd) Is an example of positive controle) None of the above
Practice Questions
• DNA binding proteinsa) Include the lambda repressorb) Can have two helicesc) Have inverted repeatsd) Can be dimerse) All of the above
Practice Questions
• A stem loop followed by a series of Uracilsa) Is part of Rho-dependant termination of
transcriptionb) Is involved in the regulation of the Trp operonc) Is a signal for translational terminationd) Is the only way to end transcriptione) All of the above
Practice Questions
• Antisense RNAa) Bind double stranded RNAb) Are 1000s of nt longc) Are down-regulated in order to turn target
genes offd) Always inhibit translatione) None of the above
Practice Questions
• Acylated homoserine lactones are:a) Found in cell membranesb) Involved in quorum sensingc) Inhibit their own synthesis as part of feedback
inhibitiond) Binds an activator proteine) B and D
Practice Questions
• This diagram of the trp leader peptide demonstrates:
a) A cell without any tryptophanb) A cell with plenty of tryptophanc) An attenuation signald) A and Ce) B and C
mRNA
uuuuu
1 2 3 4
Practice Questions
• In low tryptophan conditions, the following regions would hybridize in the trp leader mRNA
a) 1 and 2, 3 and 4b) 1 and 2, 2 and 3c) Only 2 and 3d) 1 and 4, 2 and 3e) None of the above
Practice Questions
• The role of CheB in chemotaxis isa) Phosphorylation of MCPb) Methylation of MCPc) Phosphorylation of CheAd) Demethylation of MCPe) Demethylation of CheR
ANSWERS
Practice Questions
• Who was the first person to observe bacteria? Who founded the study of Bacteriology?
a)van Leeuwenhoek/Hookeb)Hooke/Pasteurc)Koch/Cohnd) van Leeuwenhoek/Cohne) Winogradsky/Koch
Practice Questions
• A chemolithoautotroph is an organism which:a) Produces energy from lightb)Oxidizes inorganic compounds for energy,
and uses C02 as a carbon sourcec) Produces energy from light and uses C02 as a
carbon sourced) Oxidizes inorganic compounds for energy, and
organic carbon sources
Practice Questions
• A new organism is discovered and it is found to have the DNA organized in a discrete region. It is classified as a:
a)Bacteriab) Prokaryotec) Eukaryoted) Archaee) Could be any of the above (could be describing a
nucleus or a nucleoid)
Practice Questions
• The E. Coli genome:a) Is circularb) Has 2.7 million base pairsc) Has 4.68 million base pairsd) Has multiple Chromosomese) A and C
Practice Questions
• Phototrophsa) Are oxygenicb) Produce energy from Lightc) Utilize Pigmentsd) Can be anoxygenice) B, C, and D
Practice Questions
• Some Bacteria are:a) Responsible for the oxygenation of Earthb) Multicellular (eurkaryotes)c) Protists (name for single celled eukaryotes)d) Obligate intracellular parasites like
Deinococcus (Deinococcus=radiation resistant, chlamydia are intracellular parasites)
e) A and C
Practice Questions
• Methanogens are:a) Euryarchaotab) Archaec) Methane producersd) A, B, and Ce) B and C
Practice Questions
• Which of the following are evidence for the Endosymbiotic Theory?
a) Viruses can only reproduce in other cellsb) Endospores are resistant to desiccation and can
survive long periods of timec) Mitochondria and Chloroplasts are related to bacteriad) Cyanobacteria produce oxygen, and gain energy from
lighte) None of the above
Practice Questions
• Which of the following statements are true?a) Morphology is a good indicator of physiologyb) Coccus refers to spiral shaped bacteria c) The surface to volume ratio is greater for
smaller organismsd) All Prokaryotes are smaller than Eukaryotese) All of the above are false
Practice Questions
• Which of the following make up the polar headgroup of phospholipids?
a) Fatty acid residuesb) Isoprenec) Glycerold) Phosphate groupse) C and D (a and b are part of the hydrophobic
tails in different organisms)
Practice Questions
• Membrane Proteins:a) Process large molecules for transportb) Can be embedded in the membranec) Contribute to electron transport reactionsd) Can be peripheral or integrale) All of the above
Practice Questions
• Which of the following are found in bacteria membranes?
a) Sterolsb) Ester Linked fatty acidsc) Hopanoidsd) Ether Linked fatty acidse) B and C
Practice Questions
• Which of the following are properties of transport proteins
a) Can be saturated, and are specificb) Are required for all small, non-polar
moleculesc) Are Regulated by Biosynthesisd) A, Ce) A, B, C
Practice Questions
• Which of the following are found in both Gram positive and negative cell walls?
a) N-acetylmuramic acidb) Techoic acidc) Diaminopimelic acid d) Lysozyme sensitive bondse) A, C, and D
Practice Questions
• The peptidoglycan layera) Makes up 10% of the gram negative cell wallb) Is a major component of archae cell wallsc) Is only found in Gram-positive bacteriad) Contains core, and o-polysaccharidese) Is not found in Staphylococcus aureus
Practice Questions
• The periplasm:a) Is in archae and is composed of
pseudomureinb) Has the consistency of gelc) Contains endotoxind) Has very little proteine) None of the above
Practice Questions
• Gas vesicles are composed of 97% _____, and have ____ for crosslinking. Both of these proteins are ____ and allow the vesicles to be water tight and air _________.
a) GvpA, GvpB, hydrophobic, permeableb) GvpC, GvpA, hydrophobic, permeablec) GvpA, GvpC, hydrophilic, permeabled) GvpC, GvpB, hydrophilic, tighte) GvpA, GvpC, hydrophobic, permeable
Practice Questions
• Endospores are high in _____, have very little ______, and can be stained _______.
a) Calcium, acid soluble proteins, with special dyes
b) Dipicolinic acid, mRNA, neverc) Dipicolinic acid, mRNA, with special dyesd) Enzyme activity, ribosomes, normallye) Water, mRNA, with special dyes
Practice Questions
• Which of the following are cell surface structures?
a) Glycocalyxb) magnetosomesc) Sulfur Globulesd) Pilie) A and D
Practice Questions
• Chemical Gradients are senseda) Temporallyb) In Chemotaxisc) By Jedid) In response to lighte) A and B
Practice Questions
• Which of the following are macronutients?a) Cb) Kc) Cad) Nae) All of the above
Practice Questions
• Cell replicationa) Involves Fts proteinsb) Has variable generation timesc) Requires DNA replicationd) Can have generation times as lows as 20
minutese) All of the above
Practice Questions
• If there are 10 cells of an organism with a generation time of 1 hour, how many cells will there be: After 3 hours of logarithmic growth? After 5 hours in stationary phase?
a) 80, 320b) 10, 20c) 30, 50d) 80, 10e) None of the above
Practice Questions
• Which of the following are adaptations to environment?
a) Halophiles synthesizing compatible solutesb) Halophiles developing a monolayer membranec) Thermophiles having membranes with saturated
fatty acidsd) Psychrophiles having membranes with saturated
fatty acidse) A, and C
Practice Questions
• Which of the following stabilizes proteins in thermophiles?
a) Amino acid substitutions to minimize ionic interactions between residues
b) Di-inositol phosphatec) Compatible solutesd) None of a, b, or ce) a, b, and c
Practice Questions
• The internal pH of most acidophilesa) Is greater than 7b) Is around neutralc) Is less than 7d) Can be as high as 9.5
Practice Questions
• Water willa) Flow out in an isotonic environmentb) Will always move into the cell in any
conditionsc) Flow out in a hypotonic environmentd) Flow out in a hypertonic environmente) Combine with LO2 to produce the next
governor general
Practice Questions
• The following shows which type of organism?a) Obligate anaerobeb) Facultative anaerobec) Obligate aerobed) microaerophilice) None of the above
Practice Questions
• Which is the reaction catalyzed by superoxide dismutase?
a) ATP ADP + Pb) 2 H2O2 2 H2O + O2
c) 4 O2- + 4 H+ 2 H2O + 3 O2
d) 2 O2- + 2 H+ H2O2 + O2
e) All of the above
Practice Questions
• Which of the following are levels of regulation?
a) Enzymeb) Transcriptionc) Transpeptidationd) Translatione) a, b, and d
Practice Questions
• Feedback inhibition acts at the enzyme level of control, by inhibition a _____ enzyme at the ______ of a metabolic pathway.
a) Constitutive/endb) Allosteric/beginningc) Allosteric/middled) Constitutive/beginninge) Allosteric/end
Practice Questions
• DAHP synthases are:a) Involved in glutamic acid degradationb) Isozymesc) Subject to different regulatory controld) Transcriptional control elementse) B and C
Practice Questions
• Negative control:a) Includes the maltose degradation operonb) Includes both the arginine biosynthesis and
lac operonsc) Is a translational level controld) Can be regulated by inducerse) B and D
Practice Questions
• An activator protein:a) Allows the transcription of the lac operonb) Is only active in the presence of an inducerc) Must bind near the promoterd) Is an example of positive controle) None of the above
Practice Questions
• DNA binding proteinsa) Include the lambda repressorb) Can have two helicesc) Have inverted repeatsd) Can be dimerse) All of the above
Practice Questions
• A stem loop followed by a series of Uracilsa) Is part of Rho-dependant termination of
transcriptionb) Is involved in the regulation of the Trp
operonc) Is a signal for translational terminationd) Is the only way to end transcriptione) All of the above
Practice Questions
• Antisense RNAa) Bind double stranded RNAb) Are 1000s of nt longc) Are down-regulated in order to turn target
genes offd) Always inhibit translatione) None of the above
Practice Questions
• Acylated homoserine lactones are:a) Found in cell membranesb) Involved in quorum sensingc) Inhibit their own synthesis as part of feedback
inhibitiond) Able to bind an activator proteine) B and D
Practice Questions
• This diagram of the trp leader peptide demonstrates:
a) A cell without any tryptophanb) A cell with plenty of tryptophanc) An attenuation signald) A and Ce) B and C
mRNA
uuuuu
1 2 3 4
Practice Questions
• In low tryptophan conditions the following regions would hybridize in the trp leader mRNA
a) 1 and 2, 3 and 4b) 1 and 2, 2 and 3c) Only 2 and 3d) 1 and 4, 2 and 3e) None of the above
Practice Questions
• The role of CheB in chemotaxis isa) Phosphorylation of MCPb) Methylation of MCPc) Phosphorylation of CheAd) Demethylation of MCPe) Demethylation of CheR
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