[EXAMS] MICROBIO FINAL MEGA STUDY GUIDE

This is all the exams put into one quizlet.

Life on Earth through the ages evolved in the following order:

LUCA, anaerobic microorganisms, cyanobacteria (generate oxygen), multicellular life

Which of the following is/are characteristic of all microbial cells?

metabolism

Which statement about the relationship between microbes and humans is FALSE?

Most microbes are pathogenic

Which of the following is TRUE about the differences between the microbial structures of prokaryotes and eukaryotes?

Eukaryotes contain a membrane-bound nucleus and prokaryotes lack this structure

Microbiology in Historical Context: Which of the following statements is FALSE?

Louis Pasteur proved that spontaneous generation theory was correct.

In 1900, the leading cause of death in the USA of humans was infections disease. By 2016, cases of infectious diseases dropped significantly. Which intervention DID NOT contribute to the drop in infectious disease cases?

Purposely increasing exposure to contaminated sources

When are my student support hours?

W 2-4pm, F 1-2 pm

An organism of the genus Staphylococcus is ________, while an organism of the genus Bacillus is ________.

spherical / rod shaped

What opportunity for extra credit exists in this class?

Completing more than 120 points of homework

You are trying to use Koch’s postulates for establishing a causative relationship between a microbe and a disease. You isolate a pathogen from a diseased animal onto agar plates. Then you reinoculate a healthy animal and show that it causes the disease. Which step(s) are are you missing?

I. Observe that healthy animal does not contain pathogen.

II. Isolate a pure culture from the reinoculated animal confirming it is the same pathogen as before.

III. Inoculate healthy animal with bacteria from a healthy animal.

I and II

What are the Domains of cellular life?

Bacteria, Archaea, Eukarya

Which description best characterizes Archaea?

Many are extremophiles and uncultured

Which habitat contains the highest number of microorganisms on Earth?

marine subsurface

How did Louis Pasteur's swan-neck flask experiment prove/disprove the theory of spontaneous generation?

He proved that microorganisms could only grow in nutrient broth when exposed to pre-existing microbes from the air.

Which of the following types of transport systems NEVER requires energy.

porins

Which of the following statements is FALSE for describing the endosymbiotic theory?

Organelles that evolved from endosymbiosis include the nucleus.

Which of the following statements about microbial locomotion is TRUE?

Bacterial flagella is composed of a rotor and stator that rotates the flagellin filament.

What is the best way to describe swimming motility in prokaryotes?

Bacteria move in a run-tumble fashion as they sense a chemical gradient.

Based on the table of attributes given below, which of the following statements is TRUE about the three microbes?

Table 1. Microbe table

Characteristic	Microbe A	Microbe B	Microbe C
Endospore present	no	yes	no
Type IV pili	no	yes	no
Flagella	no	no	no
Morphology	rod	rod	rod
cell membrane	ether link	ester link	ester link
Lysozyme reaction	resistant	susceptible	susceptible

Microbe B is likely a Gram positive bacterium and motile

Which of the following characteristics is FALSE about how vegetative cells differ from endospores?

Vegetative cells contain dipicolinic acid making them phase dark

The following recipe is for a complex and selective media culture medium.

Peptone extract 15 g

NaCl 10 g

Lactose 5 g

KH₂PO₄ 2 g

Neutral Red 0.03g

Agar 1.5g

Distilled water 1000 ml

pH 7

False

Some Archaea and Bacteria lack cell walls. What is FALSE about these cells and the environment they live in?

Are easily engulfed and digested by the host immune response.

Cell size is influenced by cell structure. What does NOT explain why prokaryotic cells are so small?

Grow slowly because they don't get enough nutrients via passive diffusion

After performing a Gram stain, you observed that the bacterial cells stained __________. Therefore, you conclude that the cell is likely a Gram-_________ bacteria with a thin cell wall.

pink / negative

What is an example of a micronutrient?

iron

Which cell component can serve as a way for cells to attach to surfaces AND exchange genetic information?

Pili

Cellular inclusions and vesicles (vacuoles) in prokaryotic cells can serve the following purpose EXCEPT

Vacuoles protect and store DNA.

To help confirm that one of the microbes in Table 1 is a Gram positive bacteria, which of the following envelope structures would be present?

teichoic acid

Which input(s) are important for the Krebs (TCA) cycle to regenerate?

Acetyl-CoA and Oxaloacetate

Which is a defining characteristic between anaerobic and aerobic respiration?

The terminal electron acceptor

What is FALSE about fermentation?

ATP from oxidative phosphorylation

Below is a list of membrane components (with reduction potentials) that could potentially be involved in an electron transport system for iron reduction (Fe³⁺/Fe²⁺ has E₀'= +0.20V) using dihydrogen (2H⁺/H₂ has E₀' = -0.41V).

The reaction is H₂ + Fe³⁺ --> Fe²⁺ + H₂O.

component	E0' (V)
HA: Hydrogenase A (converts H2, carries both electrons and protons)	-0.50
HB: Hydrogenase B (converts H2, carries both electrons and protons)	-0.31
CX: Cytochrome (transports electrons only)	-0.13
Q: Quinone (transports electrons and protons)	+0.08
TO1: Terminal oxidase 1 (transports electrons only)	+0.18
TO2: Terminal oxidase 2 (transports electrons only)	+0.35

Note: You don’t need all components, only the components that are appropriate. While you are trying to decide which components are needed to build an Electron Transport Chain (ETC) for a bacterium, your friend draws the following ETC. 

Question: What critique do you provide to your friend about the ETC?

TO2 is more electropositive than the terminal electron acceptor Fe3+, therefore electrons can't be transferred.

Which of the following statements is FALSE about nitrogenase activity and its regulation.

Nitrogen fixation is 2NH3 --> N2

Which of the following would be used by a chemolithoautotroph as a source of energy?

(Format for molecular formula should appear as:  C₂H₃O₂^-, H₂, CO₂, H⁺)

H2

Which intermediate compound(s) in the citric acid cycle is/are often used for biosynthetic pathways (anabolic reactions)?

α-ketoglutarate, oxaloacetate, succinyl-CoA

Which metabolic strategy does NOT invoke the proton motive force for energy conservation?

fermentation

Methanogens are anaerobic organisms that are common in sediments worldwide.

From the reaction below, _____________is the electron donor and _______________is the electron acceptor.

4H₂ + CO₂ → CH₄ + 2H₂O

H2/CO2

Which reaction is more favorable? Please refer to the redox tower. 

A) H₂ + SO₄^2- --> H₂S

B) H₂ + NO₃^- --> NO₂^- + H₂O

C) H₂ + 2Fe³⁺ (pH7) --> Fe²⁺ + 2H⁺

B

If ΔG0ʹ is negative, the reaction is

exergonic and energy will be released.

What determines the direction of chemical reaction?

concentration of reactants to products

Cells that are not growing are more vulnerable to penicillin than cells actively growing.

False

Which statement best defines a heterotroph?

An organism that uses organic carbon as a carbon source

You inoculate fresh media with 1x10⁴ cells/mL and after 10 hours count 1x10¹⁰ cells/mL. What is the generation time?

0.5 hrs/generation

Turbidity measurements are commonly utilized for monitoring

planktonic cultures.

The following conditions are true about the "Great Plate Anomaly" EXCEPT

Viable plate counts and microscopic counts are the same

You want to set up cultures on Friday night so that they are ready by Monday morning (~65 hours). The culture should have undergone exactly 13 generations by the time you start your experiment on Monday.

Which temperature will you use to grow your cultures if they have the following generation times?

37C = 0.6 hours/generation

30C = 2 hours/generation

22C = 5 hours/generation

22C

Bacteria that are able to grow in humans and cause disease would be classified as

mesophiles

Which of the following statements about bacterial growth is FALSE?

In the lag phase, cell death exceeds cell division.

The cell membranes of thermophiles and hyperthermophilic bacteria typically have more _________ to increase membrane _________.

saturated fatty acids / rigidity

Microbes that live in the open ocean have the following characteristic:

psychrophile

The toxic oxygen species ______________ can be neutralized if the bacteria contains ______________ enzyme.

H202 / catalase

What is the definition of "Minimum Inhibitory Concentration" (MIC)?

The lowest concentration of an antimicrobial agent that completely prevents visible growth of a microorganism.

The use of an autoclave is the only method for killing all cells including endospores. This type of external antimicrobial agent is called

a sterilant.

What is the order of operation for DNA replication in a growing cell?

Helicase unwinds DNA, single strand binding protein protects each strand, primase adds a primer, DNA polymerase synthesizes a new strand of DNA.

What are key differences between prokaryotic genomes and eukaryotic genomes?

Bacterial genomes generally have a higher gene coding density and little to no introns or repetitive regions

T/F: The default DNA polymerase (type III) is very error-prone and will increase mutation rates.

False

When water activity outside of the cell is relatively higher than inside of the cell, water will flow:

toward inside the cell

The following is a double stranded segment of DNA and contains the beginning of a gene.

 

5ʹ G G G C C C C C A G G T A C G G A C C A T T A T A  3ʹ

3'  C C C G G G G G T C C A T G C C T G G T A A T A T 5'

 

Based on this sequence, write the sequence of the mRNA strand as it is transcribed.

5ʹ G G G C C C C C A G G U A C G G A C C A U U A U A 3ʹ

In the process of transcription, promoters are specific sequences of ________ that are recognized by ________.

DNA / sigma factors

A tmRNA is able to free stalled ribosomes because it contains the following features EXCEPT:

acts as an mRNA carrying a Rho-dependent terminase

You discover a new microbe with the ability to fluoresce under UV light. After careful genetics, you identify that the genes for fluorescent (bfp operon) are under the positive control of an activator protein Bfp-R. Synthesis of each pigment is co-repressed by a small chemical signal, an acyl-homoserine lactone (AHL).

True/False: Transcription of bfp genes occur in the absence of AHLs.

True

Which type of regulator(s) specifically binds to operator regions of DNA?

Repressors

The initiator tRNA (fMet) enters the ribosome at the ________ site.

P

Which components of protein synthesis are important for making the correct protein?

 

I) promoter

II) RBS

III) start codon

IV) aminoacyl-tRNA synthetase

II and IV

Which of the following is FALSE regarding DNA and RNA synthesis?

Both processes require an RNA primer to begin.

Which regulation checkpoint would have the fastest response to an environmental stimulus?

Post-translation

A mutation in the gene encoding the lactose repressor (LacI) that prevents lactose from binding to the LacI protein would result in

constant repression of the lac operon in the presence of lactose.

Which organism would likely be using a two-component regulatory system?

a bacterium responding to external signals like oxygen

A regulon is composed of at least two operons regulated by the same protein.

True

What are the main components of an open reading frame (ORF) in bacteria?

RBS, start codon, coding sequence, stop codon

RNAs always encode for proteins.

False

Mechanisms for controlling enzyme activity include all of the following EXCEPT

addition of short sections of new amino acid sequence.

Biofilms reduce the efficacy of antibiotics by all of the following EXCEPT:

By adhering to a surface, the flagella can not be attacked by antibiotics

How is the activity of a riboswitch controlled?

Metabolite binding can change its structure.

Which regulation mechanism would have the fastest response to an environmental stimulus?

Post-Translation

Broad spectrum antibiotics like _______________, target a wide range of microbes. On the other hand, narrow spectrum like _______________ target specific bacteria like Gram-Positive.

Quinolones/Vancomycin

Biofilm formation in Pseudomonas aeruginosa is triggered by ________ concentration of cyclic di-GMP which _______ motility.

high; decreases

Which mechanism of adaptive resistance best describes a beta-lactamase?

Enzyme that inactivates the antibiotic

A wildtype (ancestor) strain of E. coli was susceptible to tetracycline. After prolonged exposure, mutant cells appeared that could grow in the antibiotic’s presence. Testing showed that intracellular tetracycline levels were very low in the mutants compared to the ancestor.

Which mechanism most likely explains this resistance?

Activation of an efflux pump that exports tetracycline out of the cell

Small regulatory RNAs (sRNAs) play important roles in bacterial gene regulation. Which of the following best describes how sRNAs function?

sRNAs bind to mRNA molecules to enhance or inhibit translation, depending on the interaction.

All of the following are targets of currently used antibiotics EXCEPT

biofilm formation

There are four basic stages to biofilm formation. Which of the following is the correct order of these stages?

Attachment, colonization, development, dispersal

Plating bacteria on antibiotic-containing medium to find resistant mutants is an example of screening.

False

A bacterial population is treated with a high dose of antibiotic. Most cells die, but a few survive without showing any genetic changes or growth. When the antibiotic is removed, these surviving cells regrow into a sensitive population.

Which term best describes this phenomenon?

Persistence

A virus that kills its host is said to be

lytic or virulent.

The F (fertility) plasmid contains a set of genes that encode for the ________ proteins that are essential in conjugative transfer of DNA.

pili

The CRISPR system...

recognizes foreign DNA sequences that have previously entered the cell and directs the Cas proteins to destroy them.

Consider conjugation in Escherichia coli. In which of the following matings would chromosomal genes be transferred most frequently?

Hfr × F-

Mutation rates in bacteria range from 10⁸-10¹⁰ per nucleotide base, yet under certain stressful conditions mutation rates can increase. Why is the mutation rate not constant and close to zero all of the time?

Increased mutation rates can be advantageous in rapidly changing environments because some random mutations may be useful for survival.

A deleterious mutation that inactivates recA results in all of the following EXCEPT:

decrease in phage lysis

____________ viruses are more common in prokaryotic cells whereas _______________ viruses primarily infect eukaryotic cells.

Class I dsDNA/Class IV ss+ RNA

What is the most common RNA virus in the healthy human virome?

Pepper mild mottle virus PMMoV

Consider a mutation in which the change is from UAC to UAU. Both codons specify the amino acid tyrosine. Which type of point mutation is this?

silent mutation

The uptake of free DNA from the environment is referred to as ________, while the transfer of DNA with cell-to-cell contact is known as ________.

transformation / conjugation

Which statement is TRUE about viruses?

All RNA viruses contain their own nucleic acid polymerases.

The following characteristics about transposable elements are true EXCEPT for:

Can exit cells through lysis and infect nearby genomes

What is a difference between a eukaryotic virus vs a bacteriophage?

Eukaryotic viruses can transform into tumor cells whereas bacteriophage can not.

A mutagen that induces a base-pair substitution is

Nucleotide base analogs like 5-Bromouracil

What does a class III virus (dsRNA -/+) need to do to replicate in a host?

RNA-dep. RNA polymerase to synthesize RNA for a genome and translation

You sequence the genome of a novel microbe that you suspect is an endosymbiont of honey bees. Which genome characteristic would you predict is present on the genome?

A higher proportion of genes coding for DNA replication and Translation