Environmental Sensing Flashcards
what is the main take away of alternative sigma factors
they compete so the cell only wants to make them when they are needed
what do alternative sigma factors do
make large readjustments based on the environment
RpoS is expressed in the stationary phase but is undetectable in log growth, why?
Because it is made after bacteria use all of their nutrients and requires multiple stressors to be produced
What does the RpoS regulon do / why is it so highly regulated
It upregulates a lot of the stress genes / because it makes bacteria super resistant to everything even the nutrients they need to survive - also competes with RpoD for RNAP binding (rapidly degraded during exponential growth under optimal conditions)
what is needed for RpoS to be produced
inputs that lead to the transcription of the operon, sRNAs to induce translation of that transcript, antiadaptors to prevent the degradation of RpoS
what is the two component system (TCS) / what genese does it regulate
the most common way for bacteria to sense its environment - a sensor kinase in the membrane and a response regulator in the cytoplasm / almost always regulates the genes directly next to them
What system us used to prevent lyses of the cell in a hypotonic solution
the EnvZ/OmpR system
What does the EnvZ/OmpR system do
regulates the expression of OmpC and OmpF / OmpC is a narrow porin and OmpF is a large porin (lets in more ions from the environment)
How does EnvZ regulate OmpR levels
Using a kinase and phosphotase system - with high nutrients outside the cell EnvZ is in kinase form which means there is a high concentration of OmpR so there is a lower concentration of OmpF (more OmpC)
Where does OmpR bind to ompC and ompF
high and low affinity sites at the ompC and ompF promoters
What is a biofilm
group of microorganisms that stick to each other & a surface - they are embedded in an extracellular matrix composed of proteins DNA, polysaccharides & lipids
why are biofilms a problem on gall stones in the gall bladder
they are incredibly resistant and the only cure is to remove the gall bladder
what is required for the first stages of biofilm formation, why?
cyclic di gmp (c-di-GMP) / it turns down the flagella and activate the formation of type 4 pilli (downregulates motility & upregulates biofilm production)
what synthesizes c-di-GMP / what degrades it
diguanylate cyclases (DGCs) / phosphodiesterases (PDEs)
what allows cells to know how to communicate with each other / what is that
quorum sensing (QS) / the ability to detect and to respond to cell population density by gene regulation
