Micro quiz 1+2 (review)

When severely stressed by starvation, some members of a bacterial population appear to sacrifice themselves to save others by undergoing  

• programmed cell death

• the production of stress survival genes.

• a dormant state.

• a metabolic slowdown.

• production of endospores

programmed cell death

The fastest growth rate for a species occurs at temperatures where a cell’s ________ work(s) most efficiently.  

• proteins

• polysaccharides

• cell wall

• nucleic acids

• lipids

proteins

The shortest lag period would most likely be observed in the transfer  

• from complex medium to minimal medium.

• to a different pH.

• to a lower temperature.

• to a different salt concentration.

• from complex medium to fresh complex medium.

fomr complex medium to fresh complex medium

You are measuring growth in a bacterial culture. The number of viable cells remains constant, and when you check the medium, you find that the carbon source has been used up. In which phase of growth is the culture?  

• early log

• stationary

• death

• lag

• late log

stationary

Microbes accumulate ________ in the cell to prevent cell water loss in a hypertonic environment.  

• protons

• sugars

• water

• proteins

• compatible solutes

compatible sources

You have isolated a bacterium that you believe to be the causative agent of a new disease in frogs. How would you test the third of Koch’s postulates?  

• Grow a pure culture of the bacterium outside the frog.

• Determine the shape of the bacterial cells.

• Inject the bacteria into a healthy frog.

• Show that the bacterium is not present in healthy frogs.

• Isolate the bacterium from a sick frog.

inject the bacteria into a healthy frog

Human pathogens are  

• mesophilic.

• thermophilic.

• psychrophilic.

• extreme thermophilic.

• halophilic.

Mesophilic

The time between inoculation and the beginning of growth is usually called the ________ phase.  

• early log

• late log

• death

• stationary

• lag

lag

A bacterium that thrives in your stomach is most likely a(n)  

• acidophile.

• neutrophile.

• psychrophile.

• alkaliphile.

• thermophile.

acidophile

Select all that apply. The microbiome of the gut resembles a continuous culture because  

• there is no flow of nutrients and toxins are maintained in the body.

• the gastrointestinal tract functions like a chemostat.

• relative numbers of microbes are continuously maintained.

• there is no death.

• all cells stop dividing.

the gastrointestinal tract functions like a chemostat.

relative numbers of microbes are continuously maintained.

Select all that apply. Penicillin  

• was purified by Florey and Chain.

• was discovered by Alexander Fleming.

• was produced by a bacterium.

• was an accidental discovery.

• was the first antibiotic used by humans.

everything except “was produced by bacterium”

The use of an alternative terminal electron acceptor in an electron transport chain is called  

• oxygenic photosynthesis.

• heterotrophy.

• aerobic respiration.

• anaerobic respiration.

• carbon dioxide fixation.

anaerobic respiration

What was the basis for the original smallpox virus vaccine?  

• chickenpox virus

• cowpox virus

• smallpox pustules

• rabies virus

• smallpox virus

cowpox virus

You are studying life-forms in extreme environments and you have discovered a microorganism with cardiolipin, hopanoids, and ester linkages in the membrane. It also has mycolic acids, galactans, and phenolic glycolipids in the cell wall. In addition, it contains a porin similar to OmpA. This microorganism is most likely related to  

• Gram-positive bacteria.

• eukaryotic cells.

• Gram-negative bacteria.

• mycobacteria.

• archaea.

mycobacteria

Alkaliphiles use ________ force in addition to proton motive force to maintain pH.  

• potassium motive

• sulfur motive

• sodium motive

• calcium motive

• magnesium motive

sodium motive

Deinococcus radiodurans resists extreme radiation by what mechanism?

• biofilm formation

• producing multidrug efflux pumps

• endospore formation

• repairing DNA damage

• producing aquaporins

repairing DNA damage

Cyanobacterial blooms such as those observed in Lake Erie are typically due to human-caused  

• warming.

• oxygenation.

• salinity increase.

• antibiotic resistance.

• eutrophication.

eutrophocation

All the following are true about microbes and temperature EXCEPT  

• temperature affects the average rate of molecular motion.

• changes in temperature affect membrane fluidity.

• changes in temperature affect transport.

• microbes have mechanisms to control their temperature.

• every organism has an optimum temperature for growth.

microbes have mechanisms to control their temperature

How can weak acids and weak bases enter cells and cause pH stress?  

• Weak acids and weak bases do not cause stress.

• Only weak acids can cause stress by diffusing across a membrane at low pH.

• Weak bases will only cause pH stress at low pH.

• If a cell has transporters that are not well regulated, weak acids or weak bases can accumulate inside the cells and cause stress.

• At certain pH levels, both weak acids or weak bases will be uncharged, and thus are small uncharged molecules that can diffuse across a membrane and cause pH stress inside the cell.

At certain pH levels, both weak acids or weak bases will be uncharged, and thus are small uncharged molecules that can diffuse across a membrane and cause pH stress inside the cell.

Which of the following types of molecules may passively diffuse across a membrane?  

• No molecules can diffuse across a membrane.

• a small uncharged molecule such as water

• an amino acid in a low-pH environment

• a large polar molecule such as a sugar

• a weak acid in a high-pH environment

a small uncharged molecule such as water

Suppose Pasteur’s swan-necked flasks containing boiled broth became cloudy twenty-four hours after boiling. Which choice could best explain the turbidity or cloudiness in the broth without supporting spontaneous generation?  

• Endospores in the broth survived boiling and grew after the broth cooled.

• Solid material in the broth dissolved to form living organisms.

• Contaminating organisms in the broth killed by boiling became alive again after the broth cooled.

• The broth allowed light to pass through it with less interference after boiling.

• Chemicals in the broth came together to form living organisms.

Endospores in the broth survived boiling and grew after the broth cooled.

Which of the following are responsible for the CO2-fixation component of the carbon cycle?  

• organotrophs

• symbionts

• heterotrophs

• autotrophs

• lithotrophs

autotrophs

An organism that grows exclusively in the bottom of the tube of medium containing thioglycolate is most likely a(n)  

• facultative anaerobe.

• strict aerobe.

• microaerophile.

• aerotolerant anaerobe.

• strict anaerobe.

Strict anaerobe

Which of the following materials is found in aquatic bacteria and used for positioning in the water column?  

• sulfur

• FtsZ

• magnetosome

• glycogen

• gas vesicle

gas vesicle

In order for septation to begin, which process must finish first?  

• cell wall synthesis

• DNA replication

• transcription

• membrane synthesis

• translation

DNA replication

In a two-component signal transduction system, an external signal is transferred from a ________ to activate a ________ to regulate gene expression.

• phosphate; sensor phosphatase

• phosphate; response regulator

• sensor kinase; response regulator

• phosphate; sensor domain

• response regulator; transcription regulator

sensor kinase; response regulator

To activate the transcription of a gene, the inducer can bind to a(n)

• repressor protein.

• operator region.

• activator protein.

• promoter region.

• more than one of the given choices are correct.

more than one of the given choices are correct.

T/F: We had discussed in class that antibiotic resistance genes (e.g. plasmids) are best expected to be maintained in a population that do not get exposed to antibiotics.

False

Housekeeping genes are typically

• derepressed.

• under catabolite repression.

• induced.

• none of the choices apply.

• repressed.

None of the choices apply

T/F: The three stop codons are universally utilized by bacteria to terminate translation.

False

Recall my analogy regarding running a marathon with a bicycle on your back. Which of the following best applies to this analogy as discussed in class?

• Horizontal gene transfer

• Conjugation

• Loss of genes

• Transformation

• Acquisition of plasmids

loss of genes

Select all that apply. Which of the following elements become incorporated into a mRNA during transcription of a protein coding gene?

• The sigma factor binding site

• The start codon

• The transcription activator binding site

• The Shine-Dalgarno site

• The stop codon

The start codon

The Shine-Dalgarno site

The stop codon

The mRNA region that is upstream from the start codon most likely represents the site where the

• none of the choices apply.

• RNA polymerase binds to begin transcription.

• tRNA binds to the mRNA in translation.

• DNA polymerase binds to begin chromosome replication.

• RNA polymerase binds to begin translation.

none of these choices apply

Select all that apply. Which of the following promotes horizontal gene transfer between bacteria in the human gastrointestinal tract?

• Plasmids with antibiotic resistance genes in a patient not receiving antibiotic therapy

• Low diversity of bacterial species

• High bacterial cell density

• Dead bacteria as a source of extracellular DNA for transduction

• Presence of bacteriophages

High bacterial cell density

Presence of bacteriophages

Select all that apply. Transposons serve as an effective tool for identifying genes associated with a phenotype of interest since they

• can be used in an animal model screen to identify potentially important genes for human infections.

• can carry an antibiotic resistance gene as a selectable marker.

• can cause loss-of-function mutations if they integrate into a gene’s coding region.

• usually integrate in completely random locations.

• usually disrupt only a single gene per mutant.

All

Autoinducers function by

• diffusing out of the cell and binding to an extracellular transcription regulator to initiate transcription.

• accumulating inside the cell to bind repressor proteins and stop transcription.

• interacting with corepressors to either inhibit or enhance transcription.

• accumulating inside the cell to bind activator proteins and initiate transcription.

• promoting self synthesis.

Promoting self synthesis

Select all that apply. It could be beneficial for prokaryotes to take up foreign DNA since it could

• repair damaged chromosomes.

• drive genome evolution.

• allow new genetic functions.

• provide a beneficial trait.

• be used for metabolism.

All

Select all that apply. The insertion of three nucleotides in a protein coding sequence could result in

• a loss of function.

• a frameshift mutation.

• a transposition.

• a change in the protein sequence.

• a premature stop codon.

Loss of function

change in protein sequence

premature stop codon

When clouds cover the moon at night, the Hawaiian bobtail squid dims bacterial bioluminescence accordingly by

• squirting out the bioluminescent bacteria.

• squirting out the bioluminescent liquid.

• burying itself in the sand.

• squirting out the light organ.

• blocking it with its ink sac.

Blocking it with its ink sac

You have acquired a membrane that only allows small soluble molecules like DNA and proteins to pass through to the other side, but not insoluble proteins, viruses, and cells. You set up the following experiment with this membrane in between the two compartments within specialized flasks. Flask A has DNA on one side and recipient bacterial cells on the other side of the membrane. Flask B has donor bacterial cells on one side of the membrane and recipient bacterial cells on the other side. Flask C has bacteriophage on one side of the membrane and recipient cells on the other side. In which of these flasks could you observe horizontal gene transfer, and what is the name of that process?

Flask A; conjugation

Flask B; transformation

Flask A; transformation

Flask C; transduction

Flask B; conjugation

Flask A; transformation

Which proteins encoded by the lactose operon in Escherichia coli are required for the utilization of lactose?

• LacY and LacA

• LacZ and LacY

• More than one of the given choices are correct.

• LacZ and LacA

• LacZ and LacP

LacZ and LacY

Select all that apply. A feature common to all transcription regulation is

• changes in gene expression.

• sensing internal or external changes.

• activator or repressor.

• sigma factors.

• phosphorylation.

Changes in gene expression

Sensing internal or external changes

The stop codon signals the  

• RNA polymerase to stop transcribing the DNA.

• end of the gene.

• ribosome to stop translating the mRNA.

• tRNA to stop translating the mRNA.

• more than one of the given choices are correct.

Ribosome to stop translating the mRNA

When glucose and lactose are both present in the growth medium, Escherichia coli will

• consume lactose and activate transport of glucose for later consumption.

• consume glucose and lactose at the same time.

• consume lactose and shut down transport of glucose.

• consume glucose and shut down transport of lactose.

Consume glucise and shut down transport of lactose

Select all that apply. Which of the following is a strategy used by plasmids to ensure their inheritance?

• Plasmids contain housekeeping genes.

• Plasmids encode traits that may be beneficial to the host.

• High-copy-number makes it more likely that a daughter cell will inherit the plasmid.

• Partition systems aid low-copy-number plasmids by spatially controlling them.

• Plasmids trick bacteriophages for transduction.

Plasmids encode traits that may be beneficial to the host

High-copy number makes it more likely that a daughter cell will inherit the plasmid.

Partition systems aid low-copy-number plasmids by spatially controlling them.

Generalized transduction and specialized transduction differ by

• the environment where the host resides.

• either chromosomes or plasmids being transferred.

• the specific interaction of bacteriophage DNA with the host DNA.

• the specific plasmids being transferred.

• none of the provided choices.

The specific interaction of bacteriophage DNA with the host DNA

Select all that apply. A specialized sigma factor is involved in

• quorum sensing.

• the heat-shock response.

• the response of the cell to nitrogen availability.

• housekeeping processes.

• the response of the cell to starvation.

The heat-shock response

The response of the cell to nitrogen availability

The response of the cell to starvation

The five-nucleotide consensus sequence starting at the +1 site in the following image is

• more than one of the given choices are correct.

• AACGG.

• AAAGG.

• AATCG.

• GAAGG.

More than one of the given choices are correct

Which of the following should help liberate a stalled ribosome on mRNA?  

• sRNA

• tmRNA

• mRNA

• rRNA

• tRNA

tmRNA

Chaperones increase heat resistance of bacteria by

• refolding proteins damaged by heat so they function again.

• activating the expression of RpoH.

• destroying damaged proteins so the amino acids can be recycled.

• extracellular secretion of damaged proteins.

• labeling damaged proteins for destruction by proteases.

Refolding proteins damaged by heat so they function again