Module 5 Flashcards
why are bacteria important in marine environments
they are the base of the food chain and are major players in controlling the health of the ecosystem, decompose waste generated by others
what function do marine viruses serve in coral reefs
lysis of their hosts released dissolved and particulate organic matter into the water column for other species to use
microbes and plants are most commonly associated with the___
roots/rhizosphere
what is important for the formation of biofilms
quorum sensing (autoinducers) to induce communication between microbes
what is an example of interspecies biofilm
dental plaque
what is biofouling
when biofilms occur on man made surfaces (such as boat or pipe)
what is the concern with bacterial streamers
that they will block flow of liquid through a device such as a tube/catheter
what are normal flora
the organisms that live on and in our body as commensal microbes (also includes fungi - mycobiota)
features of the mycobiota
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
how is the normal flora first established in the human body
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)
what are Two Component Signal Transduction Systems (TCS)
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
what are the two components of TCS
the histidine kinase and the response regulator
What is the role of bacterial secretion systems in pathogenicity?
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.
How does bacterial secretion help in masking the bacterium from the immune system?
Secretion of surface components like toxins and adhesins can shield the bacterium from immune detection and facilitate adherence to tissues, enhancing infection.
What is the role of bacterial secretion in iron sequestration?
Some bacteria secrete proteins to sequester iron from the environment, which is critical for bacterial growth and survival, particularly in iron-limited conditions.
What is the Gram-Positive Sortase System?
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.
what are sortases
A group of prokaryotic enzymes that modify surface proteins
what are the 3 motifs required for secreted proteins by the sortase enzyme need to have to be recognized
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
What does Sortase enzyme do in Gram-positive bacteria?
Sortase recognizes and cleaves proteins with specific motifs, attaching them to the peptidoglycan layer, crucial for bacterial surface interactions and virulence.
what is the mechanism of secretion/attachment in the sortase system
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
exotoxin
Secreted by bacteria into environment, into other cells
Toxic to host
example: tetanis
endotoxin
Part of bacterial surface
Released if bacterial cell is lysed
LPS (lipopolysaccharide) is common endotoxin
Release in blood can cause shock
Bacterial Toxins
what are the three main components of the type I secretion system
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
Describe the Type I secretion system
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
what is a protein secreted by type I secretion
Haemolysin: forms pores in RBCs
an exotoxin
describe the type 3 secretion system (TTSS)
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
what are the three key areas where interactions between microbes and human cells benefit us
Protections from pathogens (stomach)
nutrient acquisition (gut)
immune system development (gut)
what is the major vitamin that our gut microbiome helps us get
B12
lactobilli have also been identified as a source of cobalmin
how does our normal microbiome interact with our immune system
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
what is dysbiosis
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)
what can perturb the gut microbiome
decrease in gut diversity
antibiotics/drugs, health issues, diet changes
what are proto-oncogenes
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)
what cell does HIV target
CD4 T cells
how does the oral environment of our teeth impact microbes
Neutral pH favours commensal streptococci
Sugar intake causes decrease in pH
Acidic pH favours cariogenic species
-streptococcus
what is an example of an oncogenic virus
hepatitis B
what are the two ways a retrovirus can lead to cncer
package host DNA into viral progeny: spread oncogenes
alteration of protein expression
chain of infection
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
