Exam 3 Lecture 23

Question 1

Components of environmental sensing and response networks (5 total)

Answer 1

stimulus; sensor; transducer; response regulator; feedback mechanism

Question 2

Sigma factor RpoD recognizes:

Answer 2

promoters of most genes (housekeeping genes that are constitutively expressed)

Question 3

Sigma factor RpoH recognizes:

Answer 3

promoter of heat shock induced genes

Question 4

Sigma factor RpoS recognizes:

Answer 4

stationary-phase and stress response genes

Question 5

Alternative Sigma factors are useful because…

Answer 5

make large readjustments in response to environment

Question 6

Heat shock response:

Answer 6

RpoH is transcribed and is degraded by DnaKJ/GrpE shunting RpoH till it reaches protease at normal temperatures. At heat stress, where other proteins are getting degraded, DnaKJ/GrpE are found fixing other proteins, leaving RpoH free, so it can go on to transcribe heat-shock genes

Question 7

DnaK, DnaJ, and GrpE are:

Answer 7

Chaperone proteins

Question 8

RNA thermometer

Answer 8

structure of RNA depends on temperature; mRNA at normal temps is bound up in stem/loop = can’t be transcribed
When temp increases stem-loops melt and mRNA for sigmaH is made and heat shock genes can be transcribed

Question 9

Two-Component System consists of:

Answer 9

sensor kinase, response regulator

Question 10

How does sensor kinase work?

Answer 10

When signal binds to receptor, autophosphorylation occurs at kinase domain intracellularly. Histidine residue gets phosphorylated and transfers phosphate to aspartate residue on the response regulator

Question 11

True or false: histidine kinase is found in many different types of cells.

Answer 11

False. Only found in bacteria.

Question 12

Each TCS (two component system) senses a distinct______ and regulates _______

Answer 12

environmental signal; distinct set of genes

Question 13

EnvZ/OmpR system is used for:

Answer 13

responding to changes in osmolarity in the environment

Question 14

Under low osmolarity conditions:

Answer 14

EnvZ acts as a phosphatase and removes phosphate from OmpR. The result is low amount of OmpR (not all or nothing process). Low amount of OmpR bind to high affinity site of ompF promoter at higher rate than is binding to low affinity site. This results in transcription of ompF gene. Larger porin will result in order to increase osmolarity.

Question 15

Under high osmolarity conditions:

Answer 15

EnvZ undergoes conformational shift to switch to kinase activity. Kinase will phosphorylate OmpR, resulting in high amount of pOmpR. They will bind to low and high affinity site of ompF, and binds to low affinity site of ompC. ompC will be transcribed, yet ompF will not be transcribed.

Question 16

micF

Answer 16

expression also driven by binding of pOmpR to low affinity site of ompC gene, which has complementarity to ompF RBS, inhibiting the transcription of ompF

Question 17

Quorum sensing

Answer 17

the ability to detect and respond to cell population density by gene regulation

Question 18

What does quorum sensing require?

Answer 18

autoinducer, receptor, transcriptional regulation

Question 19

Gram positive uses ______ for quorum sensing:

Answer 19

autoinducing peptides (AIP)

Question 20

Gram negative uses ______ for quorum sensing:

Answer 20

N-acyl homoserine lactones (AHL)

Question 21

True or false: Quorum sensing is not directly proportional to growth of bacteria

Answer 21

True - depends on certain threshold of cell population density

Question 22

Characteristic of homoserine lactone family:

Answer 22

amphipathic, can easily cross cell membrane

Question 23

QS by Vibrio fischeri causes:

Answer 23

density dependent light production

Question 24

Quorum sensing is a ______ feedback loop

Answer 24

Positive

Question 25

What do biofilms typically form from?

Answer 25

Lots of swimming planktonic cells than attach to a substrate and produces exopolysaccharide.

Question 26

Forming a biofilm is an example of _______

Answer 26

quorum sensing

Question 27

Why is it important to coordinate QS bioluminescence with cell density?

Answer 27

It takes a lot of energy to bioluminesce. Also, an individual bacterium bioluminescing isn’t that useful spending that energy.

Question 28

___% of healthy individuals have S. aureus as part of their skin microbiome; ___% carry it in their nares

Answer 28

20; 30

Question 29

True or false: Staph aureus is not a harmful pathogen.

Answer 29

False, it can be deadly

Question 30

Staph aureus QS (Agr; accessory gene regulator):

Answer 30

Has a TCS. Since it is gram(+), it uses AIP as autoinducer, which is secreted and binds to AgrC histidine kinase, which transfers phosphate to AgrA (response regulator).

Question 31

What does AgrA regulate once it is phosphorylated?

Answer 31

Activates PSMs, can bind to site on the DNA that can turn on P2 or P3.

Question 32

What is P2?

Answer 32

leads to RNAII production (agrBDCA) to cause positive feedback loop

Question 33

What is P3?

Answer 33

leads to RNAIII production

Question 34

What is RNAIII?

Answer 34

Complex RNA with large secondary structure, can activate or repress transcription other regulators in S. aureus

Question 35

True or false: RNAIII cannot be translated due to its role as a regulator.

Answer 35

False, it can be translated to form delta toxin that plays a role in the rash caused by eczema

Question 36

What is meant by sociomicrobiology?

Answer 36

bacteria are social creatures that communicate, they produce costly extracellular products as public goods when enough are around