History of Microbiology

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


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


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

DDC

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

+ -


• 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


• 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


4- can base pair with 3Followed by multiple U’s

uuuuu1 2 3 4

Attenuation

mRNA





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



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



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

History of Microbiology

Documents

Transcript of History of Microbiology