Lecture 3 Flashcards
once in the body what kind of cell do bacteria usually adhere to?
Epithelial cells
after establishment, through where do bacteria spread?
through tissues or via the lymphatic system
what are the 4 steps to the infection process?
- adhere to host cell
- spread
- survive defenses
- transfer to new host
what are some negatives for bacteria when it comes to attachment?
attachment could stimulate immune cell infiltration, activation, and phagocytosis
what are the components of adhesion for bacteria?
consists of lectin carbohydrate associations or Beta 1 integrins via ECM components for indirect association
direct interaction between what can allow bacterial entry into a host cell?
direct interaction between host integrin or cadherin receptors with bacteria surface ligand
what are the 4 big classes of the ECM?
collagen, fibronectin, laminin, and proteoglycan
what makes up collagen fibers and what about this set up is special?
it is 3 left hand helises wound to make fibrils which come to form the collagen fibers and all this winding gives it tensile strength
what is the make up of proteoglycans?
starts with a central molecule of hyaluronic acid, connected to this are then core proteins and connected to core proteins are sugars either chondroitin sulfate or keratan sulfate
what are some traits of fibronectin?
heterodimer but very close to being a homodimer, 2 proteins connected by disulfide bonds
what are some traits for laminin?
creates basal lamina which is foundation for cells to sit on, involved in general interaction and signaling, and can interact with collagen network
what are the 4 steps for pathogen induced upregulation of adhesion?
- bind
- receptor up regulation
- make more receptors
- increased adhesion
true or false: granuloma formation is always a good thing
false, granuloma formation can be both good and bad
what are some factors in bacteria-host surface interactions?
- net surface charge (on host and bacteria)
- surface hydrophobicity (if one cell is phobic and other is philic then bad bonding)
- binding molecules on bacteria and host cell receptors ( ligands and adhesins)
how small does a distance have to be for specific adhesion?
less than 1 nm, anything larger would be nonspecific adhesion (could be van der waals, electrostatic repulsion, and hydrophobic interactions)
What are some traits of nonspecific adhesion?
weak adhering, can allow colonization to surfaces that isnt subject to strong washing force (skin) but not to places with strong washing forces (urinary tract)
what are the aspects of specific adhesion?
on the bacterial surface you have the surface protein (lectins) and on the host cell you have the carbohydrate part of the glycolipid or glycoprotein
where would you find bacterial adhesins on gram negative and positive bacteria? what advantage do they provide?
on gram negative bacteria you would find the proteins on the outer membrane and on gram positive would find it on cell wall. Allow for binding from safe distance
what are the three types of adhesins?
- pili/fimbriae
- non-pilus surface proteins
- polysaccharides
what are some traits of bacterial fimbriae?
multimeric, adhesive appendages protruding many microns out allowing for farther safer connection than surface proteins
what are the consequences of adhesion?
- organism colonizes surface
- pathogen colonizes surface and secretes toxin
- colonize and form a biofilm
what is a biofilm?
a community of microorganisms, associated with a surface, and encased in an extracellular polymeric matrix
what are the types of biofilms?
simple: single species
complex: multiple species, co-aggregation, and polysaccharides trap others
what are the 4 steps for biofilm formation?
- interaction of cells with a surface or with each other
- films aggregate
- cells form an extracellular matrix
- structures differ based on organisms in film and environmental conditions
what does the Extracellular matrix of the biofilm do?
allows the emerging biofilm to grow and develop into a complex 3D structure
What are the key components of the Extracellular polymeric matrix?
polysaccharides and proteins
when it comes to polysaccharides what substance do many bacteria such as E. coli and Salmonella produce?
cellulose, many other bacteria have cellulose synthesis genes
how do humans use biofilms to our benefit?
they can be used to help treat and diagnose bacteria
What is special about Quorum sensing bacterial cells?
they communicate with each other to control signaling and gene expression, this occurs at higher cell density
what do autoinducers do and where would you find them?
they are mediators of quorum sensing found in the extracellular medium
what happens to quorum sensing cells when they exceed a particular threshold?
they are internalized and activate genes that could be responsible for virulence, competence, stationary phase etc
What are some processes that are controlled by quorum sensing?
- biolumenescence
- biofilm formation
- virulence gene expression
- sporulation
- competence
what are the 3 types of quorum sensing molecules?
- acyl homoserine lactones (AHLs)
- autoinducer peptides (AIPs)
- Autoinducer-2 (AI-2)
What exactly does do AHL’s do?
mediate quorum sensing in gram negative bacteria
and mediate exclusively intracellular communication
what synthesizes and what recognizes AHL?
synthesized by Lux I and recognized by Lux R
what do autoinducer peptides do?
they regulate competence and sporulating gene expression in gram positive bacteria
what is the receptor for autoinducer peptides?
membrane bound histidine kinase
what does AI-2 do?
induces expression of stationary phase genes and inhibition of initiation of DNA replication present in gram positive and negative bacteria
what are the steps to get to AI-2
start with SRH then with LuxS we get to DPD and with cyclization we get to AI-2
what are the three modes of interaction of invading pathogens with epithelial cells?
- bridging mechanism
- entry via specialized cells (M cells)
- entry after receptor distribution following trauma or polymorphonuclear cells transmigration
what are the main lipids in lipid rafts?
cholesterol, glycosphingolipids and sphingomyelin
What are the proteins that specifically partition into the rafts of lipid rafts, what kind are on the outer and inner leaf let?
lipid anchored proteins are the proteins, GPI-AP are on the outer leaflet and G proteins on the inner leaflet
what is signal transduction?
any process by which a cell converts one kind of signal or stimulus into another
