chapter 9 case study, signal transduction system that responds to extracellular iron

aim

study how Salmonella enterica senses different metal ions using two 2-component regulatory systems, PhoPQ and PmrAB

hypothesis

• there is cross-talk between the two systems through PmrD.

• The two component systems sense different metal ions and do the two systems talk to each other?

background

• Salmonella enterica: pathogen

• Two component systems: Sensor protein and Response regulator are found in different places in the cell. Sensor protein in the membrane, response regulator in the cytoplasm

• PhoPQ system: two-component system that senses/ responds to low levels of Mg(2+). It also induces expression of pmrD gene

  1. PhoQ: sensor protein

  2. PhoP: response regulator

• PmrAB system: system that senses/ responds high levels of Fe(2+). It also induces expression of pbgP 

  1. PmrB: sensor protein

  2. PmrA: response regulator

• Crosstalk: the two systems talking to eachother 
  

• PmrD is in the regulon of PhoPQ

• Does PmrD impact on the PmrAB component system? Can Pmrd activate PmrA independently of PmrB?

• Microbes cannot grow without aMg!! Which is why it is always included

conclusions

Step 1: To determine what signals are needed to activate PmrA

• PmrAB can be activated either by low Mg (through PhoPQ) or high Fe (independent)

Step 2: Determine what other genes PmrA possibly regulates

• PmrA regulates pbgP, ugd, and pmrC found to be involved in antibiotic resistance

Step 3: Determine if these regulators could be involved in antibiotic resistance

• Both systems promote resistance to Polymyxin B, But PmrAB confers more resistance

against Polymyxin B