Lecture 6 - Pseudomonas/CF Flashcards
What is often found in the periplasmic space of gram-negative bacteria?
- Hydrolytic enzymes
- Chemoreceptors
- Transport proteins
What is O-Ag?
The LPS of a gram negative bacteria. It can be a potent antigen, provoking strong innate and adaptive immune responses
What is the most common agent/structure for bacterial motility?
Flagella
How is chemotaxis controlled? Describe the system.
Control by the two-component regulatory system.
Steps:
- Chemoattractant goes through pore of outer membrane.
- Histidine kinase protein in the inner membrane senses the molecule and phosphorylates itself.
- The histidine kinase transfers the Pi to a response regulator in the cytoplasm.
- The activated RR leads to flagellar rotation.
What molecules can adhesins bind to? What structures can they be on?
Can bind to proteins or sugars on host cells. Found on pili (fimbriae), flagella, capsules.
What are capsules made out of and what function do they serve?
Made of a loose network of polymers of sugars, proteins, or both. They promote adherence, and provide protection against phagocytosis and environmental stresses.
What two diseases are encapsulated bacteria known to cause?
Septicemia and meningitis.
How is alginate production controlled in P. aeruginosa?
If the cell wall senses damage, a protease is activated in the periplasmic space. The protease degrades MucA (a transmembrane protein of the inner membrane that is usually bound to AlgU on the cytoplasmic side). Upon MucA degradation, AlgU is released so it can bind to RNA polymerase for transcription of the alginate genes.
What is unique about the MucA found in many patients with P. aeruginosa infection?
MucA is mutated so that it is unable to sequester AlgU. This results in constant anginate transcription.
What is quorum sensing? What molecules are involved in quorum sensing in gram positive and gram negative bacteria?
Quorum sensing is the mechanism by which bacteria sense surrounding bacterial population density, and if they should form a biofilm.
Gram positive bacteria use peptides
Gram negative use acylated homoserine lactones
Describe the process of quorum sensing.
- Bacteria release an inducer (peptide or acylated homoserine lactone).
- Inducer may be altered in environment.
- Bacterial sensor kinases bind the environmental inducers.
- Kinases phosphorylate transmitters in the bacterial cytoplasm.
- Phosphate is transferred to a response regulator.
- Phosphorylated response regulator binds to RNA polymerase/genes to alter transcription.
