Module 5 Flashcards

1
Q

why are bacteria important in marine environments

A

they are the base of the food chain and are major players in controlling the health of the ecosystem, decompose waste generated by others

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2
Q

what function do marine viruses serve in coral reefs

A

lysis of their hosts released dissolved and particulate organic matter into the water column for other species to use

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2
Q

microbes and plants are most commonly associated with the___

A

roots/rhizosphere

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2
Q

what is important for the formation of biofilms

A

quorum sensing (autoinducers) to induce communication between microbes

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2
Q

what is an example of interspecies biofilm

A

dental plaque

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3
Q

what is biofouling

A

when biofilms occur on man made surfaces (such as boat or pipe)

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3
Q

what is the concern with bacterial streamers

A

that they will block flow of liquid through a device such as a tube/catheter

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3
Q

what are normal flora

A

the organisms that live on and in our body as commensal microbes (also includes fungi - mycobiota)

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4
Q

features of the mycobiota

A

more dynamic than the microbiota

make up a smaller component of the flora

limited diversity on skin but high diversity on inside

variable environmental sources

influenced/regulated by microbes

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4
Q

how is the normal flora first established in the human body

A

Newborns acquire microbes from their mothers
* Colonize oral, nasopharyngeal cavities, then GI tract
* Colonization impacted by mode of birth, diet

Early in life, gut microbiota impacted by many factors
* Later in life, flora is more stable (apart from temporary
perturbations)

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4
Q

what are Two Component Signal Transduction Systems (TCS)

A

they detect changes in the environment, how the bacteria sense their surroundings

After detection of change outside of the cell, the TCS signals via a series of phosphorylation-dependent, post-translational, activation events

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5
Q

what are the two components of TCS

A

the histidine kinase and the response regulator

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5
Q

What is the role of bacterial secretion systems in pathogenicity?

A

Bacterial secretion systems transport toxins, adhesins, enzymes, and other factors to the cell surface or directly into host cells, aiding in infection establishment and virulence.

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5
Q

How does bacterial secretion help in masking the bacterium from the immune system?

A

Secretion of surface components like toxins and adhesins can shield the bacterium from immune detection and facilitate adherence to tissues, enhancing infection.

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5
Q

What is the role of bacterial secretion in iron sequestration?

A

Some bacteria secrete proteins to sequester iron from the environment, which is critical for bacterial growth and survival, particularly in iron-limited conditions.

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6
Q

What is the Gram-Positive Sortase System?

A

It’s a bacterial system that modifies surface proteins and attaches them to the peptidoglycan layer of the cell wall, essential for various bacterial functions like adhesion and invasion.

6
Q

what are sortases

A

A group of prokaryotic enzymes that modify surface proteins

6
Q

what are the 3 motifs required for secreted proteins by the sortase enzyme need to have to be recognized

A

1st motif: Signal peptide (gets protein through cytoplasmic membrane)

2nd motif: sorting signal called the LPXTG

3rd: positively charged amino acids, keeps protein near the surface

7
Q

What does Sortase enzyme do in Gram-positive bacteria?

A

Sortase recognizes and cleaves proteins with specific motifs, attaching them to the peptidoglycan layer, crucial for bacterial surface interactions and virulence.

8
Q

what is the mechanism of secretion/attachment in the sortase system

A

Protein translocated to periplasm by secretory machinery

Sortase recognizes, cuts LPXTG motif

Sortase transfers protein to peptidoglycan precursor Gram-Positive Sortase System

It is incorporated into the peptidoglycan: pilus structure

9
Q

exotoxin

A

Secreted by bacteria into environment, into other cells
Toxic to host

example: tetanis

10
Q

endotoxin

A

Part of bacterial surface
Released if bacterial cell is lysed
LPS (lipopolysaccharide) is common endotoxin
Release in blood can cause shock
Bacterial Toxins

11
Q

what are the three main components of the type I secretion system

A

ABC transporter in the inner membrane (ATP-binding cassette)

OMP outer membrane protein)forms a channel through the outer membrane

MFP (membrane fusion protein) connects the two

11
Q

Describe the Type I secretion system

A

ABC transports material across the cytoplasmic membrane, through the MFP and through the OMP in a single step

in to out

toxin is secreted in a single step

11
Q

what is a protein secreted by type I secretion

A

Haemolysin: forms pores in RBCs

an exotoxin

11
Q

describe the type 3 secretion system (TTSS)

A

a virulence strategy used by some bacterial pathogens to inject bacterial proteins directly into the host cell

direct conduit from the bacterial cytoplasm to the host cytoplasm

injected protein kills or manipulates host cell

structure resembles a flagellum

11
Q
A
12
Q

what are the three key areas where interactions between microbes and human cells benefit us

A

Protections from pathogens (stomach)

nutrient acquisition (gut)

immune system development (gut)

12
Q

what is the major vitamin that our gut microbiome helps us get

A

B12

lactobilli have also been identified as a source of cobalmin

13
Q

how does our normal microbiome interact with our immune system

A

it keeps it on a low level of alert so that microbes are prevented from penetrating through the gut wall and into regions of the body where they could be problematic

great diversity of microbes

13
Q

what is dysbiosis

A

dramatic change to gut microbes
decrease in diversity/imbalance

inflammation and change how nutrients are absorbed

immune system
-barrier function limited
-inflammation by immune system, more than needed, can be a very bad thing for the barrier function (bacteria enter other parts of the body)

13
Q

what can perturb the gut microbiome

A

decrease in gut diversity

antibiotics/drugs, health issues, diet changes

14
Q

what are proto-oncogenes

A

Genes involved in cell differentiation, cell growth, etc
* Mutations, changes to transcription can interfere with function
* Can change to oncogenes- Leads to uncontrolled cell growth (cancer)

14
Q

what cell does HIV target

A

CD4 T cells

14
Q

how does the oral environment of our teeth impact microbes

A

Neutral pH favours commensal streptococci

Sugar intake causes decrease in pH

Acidic pH favours cariogenic species
-streptococcus

15
Q

what is an example of an oncogenic virus

A

hepatitis B

15
Q

what are the two ways a retrovirus can lead to cncer

A

package host DNA into viral progeny: spread oncogenes

alteration of protein expression

16
Q

chain of infection

A

Pathogen must be present

Pathogen must be virulent

Host must be exposed to pathogen

Host must be exposed to enough of the pathogen to cause an infection (dosage)

Host must be susceptible to the pathogen