Regulating alternative lifestyles in entomopathogenic bacteria.

Area of Science:

• Microbiology
• Molecular Biology
• Symbiotic Relationships

Background:

• Photorhabdus and Xenorhabdus bacteria engage in a trilateral symbiosis with nematodes to parasitize insects.
• During parasitism, bacteria activate pathways for insecticidal toxins, digestive enzymes, and antibiotics.

Purpose of the Study:

• To identify the molecular signal triggering antibiotic production.
• To determine small molecules regulated by this signal.
• To elucidate the mechanism of signal recognition by bacteria.

Main Methods:

• Differential metabolomic profiling of Photorhabdus luminescens TT01 and Xenorhabdus nematophila.
• Deletion of proline transporters (putP and proU) in P. luminescens TT01 to study signaling pathways.

Main Results:

• L-proline in insect hemolymph was identified as the trigger for a metabolic shift.
• Upregulation of known virulence/antibiosis metabolites and novel metabolites by L-proline.
• Proline acquisition regulates metabolic shift and maintains proton motive force, controlling virulence and antibiotic production.

Conclusions:

• L-proline recognition by symbiotic bacteria links host environment sensing to metabolic regulation.
• Bacterial proline transporters play a key role in initiating virulence and antibiotic production pathways.
• This study elucidates a novel signaling mechanism essential for bacterial symbionts in insect parasitism.