Chemotaxis and Quorum Sensing in Bacteria

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Questions and Answers

What is the primary role of methyl-accepting chemotaxis proteins (MCPs) in chemotaxis?

To phosphorylate CheY, initiating the tumbling response.
To regulate the gene transcription of attractants and repellents.
To directly control flagellar rotation.
To monitor the concentration of various substances over time. (correct)

When an attractant binds to MCPs, the rate of CheA autophosphorylation increases, leading to increased CheY phosphorylation and clockwise flagellar rotation.

False (B)

How does the concentration of a repellent affect CheA activity and subsequent flagellar rotation?

increased rate of CheA autophosphorylation, clockwise rotation

During adaptation, CheB becomes ______ and demethylates the MCPs.

phosphorylated Signup and view all the answers

Match the molecule with resultant action:

Attractant = inhibit CheA phosphorylation Repellent = increase CheA autophosphorylation Phosphorylated CheY = clockwise rotation Phosphorylated CheB = demethylates MCPs Signup and view all the answers

What are the two molecules to which CheA-P donates a phosphate group?

CheY and CheB (C) Signup and view all the answers

CheZ phosphorylates CheY, leading to tumbles in bacterial movement.

False (B) Signup and view all the answers

What is the primary function of quorum sensing in bacteria?

monitor population density and control gene expression based on density Signup and view all the answers

Quorum sensing is active only when bacterial cell ______ is high.

density Signup and view all the answers

What type of molecule do Gram-positive bacteria and archaea commonly use as autoinducer molecules?

Peptides (A) Signup and view all the answers

Autoinducers function at low concentrations to initiate quorum sensing.

False (B) Signup and view all the answers

Quorum sensing was initially discovered through studying what mechanism in Aliivibrio fischeri?

Light emission (D) Signup and view all the answers

In Aliivibrio fischeri, what enzyme is responsible for synthesizing AHL (Acyl-homoserine lactones)?

AHL synthase Signup and view all the answers

In a two-component regulatory system, what enzymatic activity is associated with the sensor kinase?

Autophosphorylation, adding a phosphate group to itself. (B) Signup and view all the answers

Feedback loops in two-component regulatory systems always involve a kinase that rapidly adds phosphate groups to the response regulator.

False (B) Signup and view all the answers

In the EnvZ/OmpR system in E. coli, how does the system respond to low osmotic pressure?

activates transcription of the ompF gene Signup and view all the answers

In the E. coli Ntr system, NRII can switch between kinase and __________ activity depending on the nitrogen status of the cell.

phosphatase Signup and view all the answers

How does the phosphorylated response regulator (NRI-P) activate transcription of nitrogen assimilation genes in E. coli?

By oligomerizing and looping the DNA to interact with RNA polymerase and sigma factor. (A) Signup and view all the answers

What is the primary role of a phosphatase in the context of two-component regulatory systems?

To remove phosphate from the response regulator, effectively turning off the response. (D) Signup and view all the answers

Bacterial chemotaxis utilizes a completely separate signaling system from two-component systems.

False (B) Signup and view all the answers

Match the component of the Two-Component Regulatory System with its function:

Sensor Kinase = Detects environmental changes and initiates the signaling cascade through autophosphorylation. Response Regulator = Receives the phosphate group from the sensor kinase and, upon phosphorylation, regulates gene expression. Phosphatase = Removes the phosphate group from the phosphorylated response regulator. Signup and view all the answers

During transformation, what is the role of competence proteins?

Protecting single-stranded DNA from degradation until RecA binds (B) Signup and view all the answers

In transformation, any DNA that enters the recipient cell will always be successfully integrated into the chromosome.

False (B) Signup and view all the answers

Briefly describe the first key step in the general mechanism of transformation.

DNA-binding protein binds to free DNA; nucleases degrade one strand. Signup and view all the answers

In transformation, single-stranded DNA is protected by competence proteins until the protein _____ binds to the complex.

RecA Signup and view all the answers

Which of the following genetic transfer processes involves a bacteriophage?

Transduction (A) Signup and view all the answers

Transformation involves direct cell-to-cell contact for DNA transfer.

False (B) Signup and view all the answers

During generalized transduction, what is the source of DNA that gets mistakenly packaged into a viral particle?

Virtually any portion of the host genome. (C) Signup and view all the answers

Match the following steps with their descriptions in the process of transformation:

DNA Binding = Free DNA attaches to a DNA-binding protein on the cell surface. DNA Degradation = Nucleases degrade one strand of the bound DNA, allowing the other to enter the cell. Protection of ssDNA = Competence proteins protect the single-stranded DNA from degradation. Integration = RecA facilitates the integration of the single-stranded DNA into the recipient genome. Signup and view all the answers

What is the likely fate of single-stranded DNA that enters a recipient cell during transformation if it lacks homology to the host chromosome?

It is degraded by cellular nucleases. (C) Signup and view all the answers

Specialized transduction involves the transfer of any random portion of the host genome.

False (B) Signup and view all the answers

In lysogeny, the phage genome integrates into the bacterial chromosome at a ______ site.

specific Signup and view all the answers

What is the primary requirement for horizontal gene transfer via conjugation?

Direct cell-to-cell contact. (D) Signup and view all the answers

What region on a conjugative plasmid contains the genes necessary for the transfer process, such as pilus formation?

tra region Signup and view all the answers

During conjugation, both strands of the plasmid DNA are transferred simultaneously to the recipient cell.

False (B) Signup and view all the answers

What mechanism is employed by some plasmids and viruses to replicate their genome during conjugation?

Rolling circle replication. (A) Signup and view all the answers

Match each term with its correct description regarding horizontal gene transfer:

Generalized Transduction = Transfer of DNA from any part of the host genome. Specialized Transduction = Transfer of specific DNA regions adjacent to a viral integration site. Conjugation = DNA transfer requiring cell-to-cell contact. Lysogeny = Integration of phage genome into the bacterial chromosome. Signup and view all the answers

Which of the following best describes the function of alarmones like ppGpp and pppGpp in bacteria?

They trigger the stringent response to help bacteria survive nutrient deprivation. (C) Signup and view all the answers

Catabolite repression ensures that bacteria preferentially utilize alternative carbon sources even when glucose is abundant.

False (B) Signup and view all the answers

What is the primary role of the RpoS regulon in bacteria under stress?

It controls the expression of genes associated with stress resistance and adaptation. Signup and view all the answers

In E. coli, the presence of both glucose and lactose leads to a phenomenon known as _______ growth, where glucose is utilized first.

diauxic Signup and view all the answers

Match each molecule with its role in bacterial regulation:

AI-3 = A signal molecule produced by E. coli O157 Epinephrine = A stress hormone produced by host intestinal cells cAMP = A regulatory nucleotide involved in catabolite repression ppGpp = An alarmone produced during nutrient depravation Signup and view all the answers

What is the direct consequence of epinephrine and norepinephrine production by host intestinal cells during bacterial infection with E. coli O157?

Phosphorylation and activation of bacterial transcriptional activator proteins. (C) Signup and view all the answers

The RelA protein is primarily responsible for degrading ppGpp during the stringent response.

False (B) Signup and view all the answers

How does cyclic AMP (cAMP) participate in catabolite repression?

It binds to and activates the cyclic AMP receptor protein (CRP), which then affects gene expression. (A) Signup and view all the answers

Flashcards

Two-Component Regulatory Systems

A system with a sensor kinase and a response regulator for signaling.

Sensor Kinase

A protein that detects environmental changes and autophosphorylates.