Probing the barrier function of the outer membrane with chemical conditionality

Area of Science:

• Molecular Biology
• Microbiology
• Genetics

Background:

• Biological membranes control nutrient influx and toxic molecule exclusion via membrane biogenesis.
• Gram-negative bacteria possess a complex outer membrane (OM) requiring precise protein and lipid composition.
• Mutations compromising the OM can be identified by selecting for suppressors that restore membrane integrity.

Purpose of the Study:

• To investigate if structurally different toxic small molecules select for distinct genetic suppressors of OM defects.
• To identify genes involved in membrane biogenesis by selecting for resistance to bile acids in a compromised OM strain (imp4213).

Main Methods:

• Utilized a selection strategy based on resistance to bile acids in an Escherichia coli imp4213 mutant with a leaky OM.
• Isolated and characterized suppressor mutations conferring resistance to specific bile acids.
• Analyzed the function of the identified suppressor gene (yaeT) in outer membrane protein assembly.

Main Results:

• A suppressor mutation in the yaeT gene was identified, conferring resistance to a specific subset of bile acids.
• YaeT is an essential protein involved in the assembly of beta-barrel proteins in the bacterial OM.
• The identified suppressors demonstrated remarkable chemical specificity, indicating distinct solutions for different toxic molecules.

Conclusions:

• Structurally diverse toxic small molecules select for highly specific genetic solutions to correct membrane permeability defects.
• The study provides insights into the molecular mechanisms underlying the outer membrane permeability barrier in bacteria.
• YaeT's conserved role in OM biogenesis across species highlights its fundamental importance.