MBIO 3401 Exam 1 Study

Fall 2024 TTU Microbiology Exam 1 study guide

Koch’s Postulates

1. Microbe is in all cases of the diseased, but absent in healthy individuals

2. The microbe is isolated from the diseased host and grown in a culture

3. When the microbe is introduced to the healthy host, disease occurs

4. The same microbe strain is obtained from the newly diseased host

The criteria for establishing a causative link between an infectious agent and a disease

Koch’s Postulates

inoculated smallpox

Lady Mary Montagu

Made vaccination for smallpox from cowpox

Edward Jenner

Developed vaccines from weakened strains

Louis Pateur

Immunization

Stimulation of an immune response by deliberate inoculation with a reduced pathogen

Ignaz Semmelweis

ordered doctors to wash hands with chlorine and mortality rates decreased

Joseph Lister

Used carbolic acid to treat wounds and clean surgical tools

What are the principles for effective light microscopy?

Contrast, magnification, a wavelength smaller than the object, proper lighting, and focused lenses

Which methods in microscopy use interference?

Phase contrast microscopy (PCM) such as differential interference contrast microscopy (DIC)

Fluorescence Microscopy

specimen absorbs light of a defined wavelength and then emits lower light with longer wavelength so that specimen glows

Used to view marine and pathogenic bacteria

type of interference microscopy

Chemical Imaging Microscopy

uses mass spectrometry to see chemicals in cells

Dark-field optics

microbes appear as halos of bright light against darkness

detects of very narrow cells unresolved by bright-field microscopy

Phase-Contrast Microscopy (PCM)

uses differences in refractive index between the cytoplasm and the surrounding medium/organelles

Used to see live cells and organelles

Paramecium

30 um; visible to human eye; stained light microscopy

Pseudomonas

5 um; stained light microscopy

E. Coli

transmission electron microscopy

Ribosomes on mRNA

transmission electron microscopy

Autotrophs

gain energy from fixing CO2 and assemble into organic molecules

Heterotrophs

gain energy from organic molecules

Phototrophs

gain energy from chemical rxns triggered by light

Chemotrophs

gain energy from oxidation reduction rxns

Lithotrophs

gain electrons from inorganic molecules

Organotrophs

gain energy from organic molecules

Generation Time - time it takes for a population to double

(final cell number) = (original cell number) x (2^(n ~ number of generation)

Nt = N0 × 2^n

Extremophiles

organisms inhabiting any ecological niche outside normal conditions

Hyperthermophile

grows in temps >80 C

Alkaliphile

grows above 9 pH

Halophile

grows in high salt content

Barophile

growth at pressure >380 atm

Thermophile

grows in temps 50 C - 80 C

Mesophile

grows in temps 15 C - 40 C

Acidophile

grows below 3 pH

Psychrophile

grows at temp <15 C

Who developed the earliest immunizations? What diseases were they for?

Louis Pasteur (1822-1895) developed the first vaccines based on attenuated (weakened) strains.
-Fowl cholera
-Rabies

Microbes live and grow just about everywhere on Earth, except:
A) Between your teeth after brushing and flossing.
B) On your cell phone.
C) In microscopic aerosols that we breathe.
D) Above 100°C or below minus 40°C.
E) None of the above.

E) None of the above

The first vaccination was performed by
and the first antibiotic was discovered
by
A) Lady Montagu; Louis Pasteur
B) Edward Jenner; Louis Pasteur
C) Edward Jenner; Alexander Fleming
D) Louis Pasteur; Alexander Fleming
E) Louis Pasteur; Edward Jenner

C) Edward Jenner; Alexander Fleming (penicillin)

Which of the following statements about the size of microbes is FALSE?
A) Eukaryotic microbes tend to be 2-20 nm.
B) Prokaryotic microbes tend to be less than 10 um.
C) A few bacterial species are large enough to be seen by the unaided eye.
D) None of the above statements is false.

C) Eukaryotic microbes tend to be 2-20 nm.

Which of the following transport mechanisms is unique to prokaryotes?
A) Simple diffusion
B) Facilitated diffusion
C) Coupled transport
D) Siderophores
E) Group translocation

E) Group translocation

All of the following statements about ABC transporters are true EXCEPT
A) They require energy
B) They are found only in prokaryotes
C) They can be used for import and export
D) They are the largest family of transporters
E) They are found in eukaryotes and prokaryotes

B) They are found only in prokaryotes

What kind of culture transfer would most likely result in the shortest observed lag period?
A) From a complex medium to a fresh complex medium
B) From a complex medium to a minimal medium
C) to a medium at a different temperature
D) to a medium at a different pH

A) From a complex medium to a fresh complex medium

Bacterium Thi scourse has a generation time of 20 minutes. Starting with one cell in log phase, how many minutes does it take to produce about 1,000 cells? Assume all cells remain viable.

200

Why can't bacteria grow in solutions with very high concentrations of sugar?
A) Bacteria cannot digest pure sugar
B) Sugar contains toxic reactive oxygen species (ROS)
C) Sugar lowers the solution's osmolarity
D) Sugar raises the solution's osmolarity
E) Sugar raises the solution's pH

D) Sugar raises the solution's osmolarity

Which organism will grow most evenly throughout a tube of thioglycolate broth medium?
A) Strict aerobe
B) Microaerophile
C) Facultative aerobe
D) Aerotolerant anaerobe
E) Strict anaerobe

D) Aerotolerant anaerobe

Which of the following is NOT correctly defined?
A) Sanitation: killing of all living organisms
B) Disinfection: killing or removal of pathogens from inanimate objects
C) Sterilization: killing of all living organisms
D) Antisepsis: killing or removal of pathogens from the surface of living tissues
E) None of the above

A) Sanitation: killing of all living organisms

Laminar flow biosafety cabinets typically force air through HEPA filters which
-remove ~ 90% of airborne particulates 3 um or larger
-remove > 99.9% of airborne particulates 0.3 um or larger
-remove ~90% of airborne particulates
30 um or larger
-remove > 99.9% of airborne particulates 0.3 nm or larger mm or larger
-remove only airborne particulates 3

remove > 99.9% of airborne particulates 0.3 um or larger

What is the molecular basis of the antibiotic action of Penicillin?
-Penicillin inhibits protein synthesis
-Penicillin inhibits DNA replication
-Penicillin prevents peptidoglycan synthesis
-Penicillin prevents cell wall formation
-C and D

C and D

Which of the following statements about membrane lipids is true?
-Lipids of bacteria have ether linkages, while those of archaea have ester linkages.
-Lipids of bacteria have ester linkages, while those of archaea have ether linkages
-Lipids of bacteria and archaea have ester linkages.
-Lipids of bacteria and archaea have ether linkages.

Lipids of bacteria have ester linkages, while those of archaea have ether linkages

Which of the following is NOT a component of peptidoglycan?
-Peptide cross-links
-Amino acids
-Lipopolysaccharide
-N-acetylglucosamine
-N-acety|muramic acid

Lipopolysaccharide

All of the following are true about the prokaryotic outer membrane EXCEPT:
-It is composed of a simple phospholipid bilayer.
-It is found only in Gram-negative bacteria.
-It contains porins.
-It contains a toxic component.
-It contains a lipopolysaccharide layer.

It is composed of a simple phospholipid bilayer.

which of the following is a key tool used in cell fractionation?
-Autoclave
-DNA sequencer
-Thermocycler
-Ultracentrifuge
-Electron microscope

Ultracentrifuge

Prokaryotic chromosomes have:
-one origin of replication per chromosome and DNA is replicated unidirectionally
-one origin of replication which replicates and migrates as DNA is replicated bidirectionally multiple origins of replication per chromosome, with DNA replicated unidirectionally
-multiple origins of replication per chromosome, with DNA replicated bidirectionally

one origin of replication which replicates and migrates as DNA is replicated bidirectionally

All of these statements about prokaryotic flagella are correct EXCEPT:
-They are driven by the proton motive force.
-They are found in both Gram-positive and Gram-negative bacteria.
-Their motor is embedded in the cell envelope.
-They are used for chemotaxis.
-They move with a whiplike motion.

They move with a whiplike motion.

If the sequence of one strand of DNA is 5' TCGATC 3', what is the sequence of the complementary strand?
-5' CTAGCT 3'
-5' GCTAGC 3'
-5' AGCTAG 3'
-5' GATCGA 3'

5' GATCGA 3'

Which statement is correct about topoisomerases?

-Type I topoisomerases relieve

supercoiling by cleaving both strands of DNA

-Type Il topoisomerases introduce supercoiling by cleaving one strand of

DNA

-Type Il topoisomerases do not relieve supercoiling by cleaving both strands of DNA

-Type I topoisomerases relieve supercoiling by cleaving one strand of DNA§Replication ends at defined termination (ter) sites located opposite to the origin.

Type I topoisomerases relieve supercoiling by cleaving one strand of DNA

Which of these represents a correct order of proteins involved in bacterial DNA replication?
-DnaA → DNA pol Ill → primase → ligase
-Primase → DNA pol III → DnaA → ligase
-DnaA → primase → DNA pol llI → ligase
-Primase → DNA pol Ill → ligase → DnaA

DnaA → primase → DNA pol llI → ligase

Plasmids are usually transferred from one bacterium to another via the process of?
-transformation
-transduction
-transfection
-coinfection
-conjugation

conjugation

NGS stands for?
-Nick Generation Sealing
-Next Genomics Sanger
-Next Genome Sequencing
-Next Generation Sequencing
-Novel Genetic Sequencing

Next Generation Sequencing

Error-proof repair pathways include all the following EXCEPT
-photoreactivation
-base excision repair
-nucleotide excision repair
-nonhomologous end joining

nonhomologous end joining

The protein response_____is the activator of the SOS
-DNA pol Ill
-UvrD
-RecA
-LexA
-HisG

RecA

which list includes examples that are not examples of prokaryotic DNA transfer mechanism
-conjugation, transduction, and transformation
-vesicles nanotubules and phage-like gene transfer agents
-type IV pilus in transformation, and specialized transduction
-Hfr transfer of chromosomal genes via T4SS and conjugation
-recombinational repair and nucleotide excision repair of the conjugant pilus

recombinational repair and nucleotide excision repair of the conjugant pilus

which list includes examples that are NOT examples of prokaryotic DNA transfer mechanisms
-conjugation, transduction, and transformation
-vesicles, nanotubules, and phage-like gene transfer agents
-Hfr transfer of chromosomal genes via T4SS, and conjugation
-recombinational repair, and nucleotide excision repair of the conjugant pilus

recombinational repair, and nucleotide excision repair of the conjugant pilus

The sigma factor is directly required for
-transcription initiation
-Transcription elongation
-Translation initiation
-Translation elongation

transcription initiation

which of these represents a correct order of proteins involved in bacterial translation
A) EF-Tu -> IF2 -> RF3 -> EF-G
B) EF-Tu -> EF-G -> IF2 -> RF3
C) IF2 ->EF-Tu -> EF-G -> RF3
D) IF2 ->EF-G -> EF-Tu -> RF3

C) IF2 ->EF-Tu -> EF-G -> RF3

chaperones are the protein that
- initiate catalysis via chaperonin
-help guide or "chaperone" proteins to their substrates
-degrade misfolded proteins
-help proteins fold properly

help proteins fold properly

What historical person and intervention contributed most famously to modern day understanding of sanitation to reduce pathogenic bacterial transmission in clinical settings?

1847, Ignaz Semmelweis ordered doctors to wash their hands with chlorine (antiseptic agent)

developed carbolic acid to treat wounds and clean surgical instruments.
Suddenly postpartum maternal death rates fell.

Joseph Lister

What do Koch's Postulates state? Why is each postulate important?

1. Microbe is always present in diseased host.
- absent in healthy
2. Microbe is grown in pure culture.
- no other microbes present
3. Pure microbe is introduced into healthy host.
- Individual becomes sick.
4. Same microbe is re-isolated from now-sick individual.

Criteria for establishing a causative link between an infectious agent and a disease

Koch's Postulates

What key principles make light microscopy effective? Which methods in microscopy use interference?

resolves images of individual bacteria by their absorption of light. (resolution, detection, and magnification) dark object against a light field.
Differential interference contrast microscopy
Phase-contrast microscopy (PCM)

Paramecium stained light microscopy

Pseudomonas light microscopy

C. Escherichia coli transmission electron microscopy, TEM

Ribosomes on messenger RNA transmission electron microscopy, TEM

Ribosome model (X-ray crystallography)

2 um – 20 cm

Protozoa, algae, fungi
-Structures can be seen under a light microscope.

-0.4 –10 mm

bacteria, archaea
-Subcellular structures too small to resolve by light microscopy

wave length of visible light

400-750 nm

Problem-solve a microscopy experiment: given cells with features you hypothesize to be present, but cannot see, choose an alternate microscopy approach.

bright field mircroscopy employs various stains
fluorescence employs fluorophores for labeling
Generates a dark image of an object over a light background

What are the terms for organismal classification based on biomass and carbon acquisition?

Autotrophs fix carbon dioxide and assemble into organic molecules (mainly sugars). (e.g. photoautotrophs, chemolithoautotrophs/lithotrophs)

Heterotrophs use preformed organic molecules. (e.g. photoheterotrophs, chemoheterotrophs/organotrophs)

use light energy or oxidation of minerals to capture CO2 and convert it to complex organic molecules.

autotrophs

degrade complex organic compounds (polysaccharides) through the tricarboxylic acid (TCA) or fermentation.

heterotrophs

All life is based on carbon, acquired in different ways.

biomass

use preformed organic molecules. (e.g. photoheterotrophs, chemoheterotrophs/organotrophs)
some can be photosynthesized

Heterotrophs

obtain energy from chemical reactions triggered by light.

phototrophs

obtain energy from oxidation-reduction reactions.

chemotrophs

use inorganic molecules as a source of electrons.

lithotrophs

use organic molecules.

organotrophs

If a cell divides by binary fission, the

number of cells is proportional to 2n.

Final cell original number = cell number x 2^(number of generations)

Nt=N0x2^n

Imagine Bacillus cereus divides once every 30 minutes. If we begin a culture with 100 cells, how many bacteria will we have after 3 hours of logarithmic growth?

6400

What if you already know your Bacillus cereus culture has 6,400 cells and you began with 100 cells and incubated it at log growth for 3 hrs. How many generations of growth occurred? log Nt = log (N0) + nlog2

6 generations

What is the formula for log growth? How is this formula used to calculate the starting and final numbers of cells relative to the number of generations under log growth?

Nt = N0 x 2n

Where Nt is the final cell number,

N0 is the original cell number, and

n is the number of generations.

Any ecological niche outside this window is called "extreme," and organisms inhabiting them are called
Temperature > 100°C; pH 2

extremophiles

Sea level; Temperature 20oC-40oC; near-neutral pH; 0.9% salt; and ample nutrients

normal growth conditions

grow above 80 C

hyperthermophile

50 C-80 C

thermophile

15- 45 C

mesophile

grow below 15 C

psychrophile

grow above pH 9

alkaliphile

pH 5-8

neutrophile