Serratia Quorom Sensing Flashcards
(22 cards)
What is an opportunistic pathogen?
A microbe which has the potential to cause disease in an immunocompromised patient
What is prodigiosin?
An antibiotic secondary metabolite produced by Serratia which produces a red pigment (associated with the cell membrane)
What is carbapenaem?
A secondary metabolite antibiotic which is secreted and diffusible
How would secondary metabolites benefit serratia?
They might diffuse into host and kill other competitive microbes
What is the key signaling molecule for quorum sensing?
AHL
What is quorum sensing?
The to a chemical signal in good growth conditions - causing the switching on of genes for virulence factor production
What specifically does a peak threshold of the autoinducer activate?
Activates a regulatory binding protein to switch on virulence genes
What is cross feeding?
Cross feeding can be used to determine the order of action of genes in a metabolic pathway - can a mutant restore the pathway in a different mutant?
What are pleiotropic mutants?
Several phenotypes caused by mutation in one master regulator gene
What is swarming?
Swarming is the ability of some bacteria to move over a solid surface as a coordinated group
How was serratia mutagenized in our specific experiments?
transposon mutagenesis using Tn5 which carries a resistance gene for kanamycin
How can you select for transformed cells of our original serratia population?
transposon contains kanamycin resistance - all colonies which can grow on kanamycin will have transposon inserted somewhere in their genome (not in essential genes)
What indicator is used to test for Car mutants?
E.coli is used to test for the production of Carbapaneam (halo of death)
What indicator is used to test for AHL production?
Chromobacterium violaceum
How can chrombacterium violaceum act as an indicator?
Mutated species CV026 does not produce AHL. Only produces violet pigment in the presence of external AHL (ie is serratia producing AHL or not)
Why might a serratia mutant have a hyperpigmented phenotype?
Because it overproduces a primary metabolite
In cross feeding, is the ‘feeder’ later or earlier in the biosynthetic pathway than the ‘fed’?
The feeder is later in the pathway, and fed is earlier in the pathway
How can a mutant feed another?
If the mutant later in the pathway is close to a mutant with mutation earlier, the first mutant (A) will accumulate the intermediate and will eventually secrete it - the other mutant (B) will have the correct enzymatic machinery to turn this intermediate into the final product (just didn’t have correct machinery to produce intermediate which it has just been fed by A)
What is the phenotype of a LIS mutant of serratia?
no red pigment but an intact biosynthetic pathway (cannot produce AHL but can respond to it)
What do soft agar swarming microbes rely on for swarming ability?
Soft agar microbes rely on the secretion of a powerful biosurfactant to swarm - under quorum sensing control
How can swarming benefit a pathogenic cell?
Ability to invade tissue and colonise/ overcome host defences
What technique would you use if you wanted to study mutations in essential genes?
Conditional mutants - ie temperature sensitive mutants
mutagenize with alkylating agent - EMS
