Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Microbial Physiology > Lecture 2 - Exam 5 > Flashcards

Lecture 2 - Exam 5 Flashcards

1
Q

Most of the laboratory-based microbial research utilizes large volumes of bacteria grown planktonically in pure culture:
Reproducible, rapid, simple, “synchronized” growth, and defined media.
Do bacteria grow like this in nature?

A

Bacteria almost never grow that way in nature.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Where do most bacteria grow?

A

The vast majority of bacteria grow in heterogenous assemblages, attached to a surface within a biofilm.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is a biofilm?

A

A strong and dynamic structure that confers a broad range of advantages to its members, including:
-Adhesion/cohesion capabilities and mechanical properties
-Nutritional sources
-Metabolite exchange platform
-Cellular communication
-Protection and resistance to drugs* (antimicrobials, disinfectants), environmental stresses (dehydration and ultraviolet light), host immune attacks (e.g. antibodies, phagocytes), and shear forces

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Biofilms are communities of microorganisms, affixed to…?

A

Affixed to a living or non-living surface within a self-made matrix that joins them together

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Biofilms are characterized by?

A

Structural heterogeneity, genetic diversity, complex community interactions, and an extracellular matrix of polymeric substances (allows them to adhere together)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is the biofilm matrix comprised of?

A

Exopolysaccharides, lipids, lipopolysaccharides, extracellular DNA (eDNA), proteins, polysaccharide-producing exoenzymes.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Can multiple cell types develop in a biofilm community?

A

Yes.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What kind of cellular communication is there between bacteria in a biofilm?

A

Intricate cellular communication between other genera and species of bacteria.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

The complex biofilm matrix plays a vital role in?
How?

A

Biofilm resistance.
-Limits penetration of bacteriocins/host immune cells, leading to increased virulence and development of multi-drug resistance
-Prevents removal via mechanical disruption
-Transfer of genetic material between cells (horizontal gene transfer) results in the evolution of more tolerant, more persistent species

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What do the social connections in biofilms look like?

A

Social connections include positive (cooperation) and negative (competition) interactions between bacterial cells that result in the remodeling of the biofilm community.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What is cooperation (positive interaction) mediated by?

A

Electrical and chemical communication between cells in biofilms.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What is competition (negative interaction) mediated by?

A

Different killing strategies (producing bacteriocins, antibiotics, enzymes, and growth inhibition & depletion of nutrient).

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

While most biofilm bacteria are cooperators (they contribute to the biofilm community), there are some considered…?

A

Some utilize the biofilm’s public goods, but contribute nothing to the community, called cheaters.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Biofilms are comprised of multiple microenvironmental niches, and consist of many subpopulations, including?

A

-“younger,” metabolically-active cells
-Metabolically inactive cells
-Persister cells (not really growing, just sitting there)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What kind of gradients develop within mature biofilms?

A

Oxygen, pH, and nutrient gradients.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

T or F. A biofilm with a few component species represents a small diversity of microhabitats.

A

False. A biofilm with only a few component species may represent a very large diversity of microhabitats.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

The concentration of a substrate that is consumed in the biofilm [decreases/increases] with depth into the biofilm and distance away from the source.

A

Decreases

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Is a metabolic product [more/less] concentrated inside the biofilm?

A

More

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

T or F. Metabolic intermediates can be consumed and produced within the same biofilm.

A

True

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Discuss the competition for a metabolic substrate between multiple biofilm bacteria.

A

Multiple biofilm bacteria may be in competition for a given metabolic substrate.
-Waste product of one species are often the metabolic substrate of another
-Waste products of a given species may be inhibitory unless removed by diffusion or metabolism by a second species.
-Metabolic intermediates may be used in various ways by different species

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What are the steps for biofilm formation?

A
  1. Reversible surface attachment
  2. Irreversible surface attachment
  3. Biofilm proliferation
  4. Biofilm maturation
  5. Active and passive dispersal
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

Describe the reversible surface attachment step of biofilm formation.

A

-Motile, chemotactic response
-Producing conditioning films on surfaces

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Describe the irreversible surface attachment step of biofilm formation.

A

-Production of adhesins (pili, fimbriae, capsule)
-Cell-to-cell communication molecules produced

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

Describe the biofilm proliferation step of biofilm formation.

A

-EPS production
-Specific cell interactions
-Quorum sensing

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

Describe the biofilm maturation step of biofilm formation.

A

-EPS accumulation
-Quorum sensing
-Established microenvironments
-Bacterial adaptations

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

Describe the active and passive dispersal step of biofilm formation.

A

-Seeding and/or sloughing of motile cells

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

There are changes in gene expression when there is surface attachment and biofilm formation. What are these changes?

A

Increase in EPS production, increase in lateral flagella/pili, increase in secreted proteases, toxins, and degradative enzymes.

28
Q

Bacterial community living provides a setting for bacteria to communicate using __________ signals.
These signals are interpreted by ?
The sensing of these signals can cause?

A

Chemical.
These are interpreted not just by members of the same cell species, but by other microbial species that are part of the same biofilm community.
The sensing of these signals can cause the neighboring cells to behave differently by modulating gene expression in those cells (quorum sensing)

29
Q

How do cells “Talk” to each other?

A

Quorum sensing.

30
Q

Quorum sensing was first introduced to describe…?

A

cell density-dependent signaling in bacteria.

31
Q

What is the process of quorum sensing?

A

Is a process of bacterial cell-to-cell communication involving the production and detection of extracellular signaling molecules called autoinducers.*
Quorum sensing allows G+ and G- bacteria to sense one another.

32
Q

Quorum sensing can be divided into 4 steps. What are they?

A
  1. Production of small biochemical signal molecules by the bacterial cell
  2. Release of the signal molecules, either actively or passively into the surrounding environment.
  3. Recognition of the signal molecules by specific receptors once they exceed a threshold concentration.
  4. Changes in gene regulation in response to signal molecules.
33
Q

What happens when the autoinducers reach a critical threshold level?

A

They activate bacterial quorum sensing genes that enables the bacteria to behave as a multicellular population rather than as individual single-celled organisms.

34
Q

What are the processes commonly regulated by quorum sensing?

A

Cell division, biofilm development, exopolysaccharide production, cell aggregation, and bioluminescence (in Vibrio species).

35
Q

Quorum sensing is helps regulate genes based on cell density.
-What kind of bacteria have QS?
-What kind of communication exists?
-What is communication mediated by?

A

-G+ and G- have QS, but mechanisms are different
-Existence of intraspecies/interspecies communication
-Communication mediated by soluble factors:
*Autoinducers that are produced at a low constitutive level and build up to higher concentration as cell density increases

36
Q

What are autoinducers?

A

Small molecules or proteins produced by bacteria that regulate gene expression.

37
Q

What are the advantages of coordinated gene regulation?

A

Coordinated production of virulence factors and coordinated production of defensive measures.

38
Q

What are the disadvantages of coordinated gene regulation?

A

Low density cells may not be as likely to survive.

39
Q

Give an example of a cell density-dependent response in pathogens.

A

Opportunistic bacteria, such as Pseudomonas aeruginosa, can grow within a host without harming it, until they reach a certain concentration. Then they become aggressive, their numbers sufficient to overcome the host’s immune system and form a biofilm, leading to disease.

40
Q

Give an example of cell density-dependent responses in beneficial bacteria.

A

The regulation of light production in Vibrio fischeri, a bacterium that lives as a symbiont in the light-producing organ of the Hawaiian bobtail squid.
When V. fischeri cells are free-living, the autoinducer is at low concentration and thus the cells do not luminesce. In the light organ of the squid, they are highly concentrated and transcription of luciferase is induced, leading to bioluminescence.

41
Q

Describe the QS in G+

A

Autoinducers are transported across the membrane by dedicated ABC transporter.
When autoinducers build a high level, autoinducer is recognized by a histidine kinase of a 2 component regulatory pathway.
Phosphorylation of a DNA-binding protein (D) regulates gene expression.
The QS and 2CR pathway are intimately linked.
EX: Competence and sporulation in Bacillus subtilis

42
Q

Describe the QS in G-

A

The autoinducer is most commonly an acyl homoserine lactone (AHL).
Most AHLs freely diffuse across membranes (in/out).
When high AHL accumulates internally, AHL binds to a response regulator (RR, in this case LuxR), and induces conformational change of RR.
RR induces gene expression

43
Q

Autoinducers are ______peptides.

A

oligo

44
Q

Many species of G- bacterial QS resemble…?

A

V. fischeri QS

45
Q

Describe the quorum sensing for the bobtail squid.
(What happens at low cell density? high cell density?)

A

Low cell density:
-Low level constitutive expression of luxl genes results in Luxl production of AHL but too low for light production.
-AHL diffuses out of the cell.
High cell density:
-AHL concentration increases
-AHL diffuses into the cell and binds to LuxR
-LuxR stays as monomer without AHL
–> receiver domain = AHL binding
–> effector domain = multimerization and DNA binding
-LuxR is a transcriptional regulator that binds to the lux box in the promoter region of the lux operon and induces gene expression.
-Results in light production by expression of luciferase enzyme.

46
Q

Elements of the autoinducer type 2 (AI-2) system are detectable in almost _________ of all sequenced bacterial genomes.

A

one-half

47
Q

What is Autoinducer type 2 important for?

A

Interspecies communication

48
Q

The Autoinducer type 2 system is recognized as?
It is important for bacteria within…?

A

The most ubiquitous signaling system employed by both G- and G+ bacteria.
Important for bacteria within mammalian gut. These bacteria may be able to stimulate mammalian cells to produce an AI-2.

49
Q

AI-2 is actively transported by an _______ transporter, where it is ________ and then binds a _________.

A

ABC ; phosphorylated ; response regulator

50
Q

To interfere with QS, bacteria use _________________ to ?
They also use __________ to ?

A

Quorum sensing inhibitors to block the action of AIs.
Quorum quenching enzymes to degrade signaling molecules.

51
Q

What is QS competition inhibition?

A

Competition with the autoinducer signal, by binding of a molecule to the response regulator, which thereby prevents its function.

52
Q

What is quorum quenching?

A

The autoinducer is bound, or degraded, to prevent the signal from being received by a receptor.

53
Q

What do you need to know about intraspecies communication?

A

Plants and animals can produce mimics that manipulate bacteria.

54
Q

What are public goods?

A

Products of microbial cooperative behaviors. These are molecules that are secreted by cells and perform their function outside. Once secreted, these molecules can diffuse away and potentially benefit other cells.

55
Q

Bacterial public goods are often under?

A

QS regulation

56
Q

Public goods within a biofilm may include:

A

extracellular enzymes, exopolysaccharides, antimicrobials, virulence factors (for fighting a host organism’s immune system, or for exploitation of host resources), siderophores.

57
Q

Public goods allow the biofilm community to survive, but also?

A

Cost a lot of energy to produce

58
Q

How was social cheating discovered?
What did the social cheaters gain?

A

When scientists repeatedly cultured chronic isolates of P. aeruginosa that were defective for AHL-mediated QS.
The social cheaters gain potential advantage of not expending energy for the good of the community but save the energy for their own growth and needs.
These cheaters are less able to withstand some cellular stresses including ROS because QS is important for detoxification of these stressors.

59
Q

To discourage over abundance of social cheaters, QS also induces some?

A

metabolic advantages of participating in production of public goods (growth advantages of catabolism of certain nutrients such as adenosine).

60
Q

Can biofilms be a serious threat to human health?

A

Yes. Fragments of biofilm can slough off at intervals and can spread the infection to distant locations within the body, becoming systemic.

61
Q

Are all biofilms bad?

A

No! They are used to break down toxic chemicals and used to produce useful biological compounds, including medicines.

62
Q

Plants have microbial populations associated with their?

A

Roots

63
Q

What is the rhizosphere?

A

The region surrounding plant roots and root hairs, that supports a complex microbial assemblage.

64
Q

The rhizosphere association is? (parasitic, mutualistic)

A

Mutualistic

65
Q

Describe what the microbes and plants get out of the rhizosphere association.

A

For microbes:
Plant roots secrete significant amounts of sugars, amino acids, vitamins, and plant hormones which stimulates microbial growth.
For the plant:
The microbial population may facilitate the absorption of nutrients by the plant from the soil. This may also help prevent disease due to infection by bacterial pathogens.

Microbial Physiology (22 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions