Phosphate uptake by the phosphonate transport system PhnCDE.

Area of Science:

• Microbiology
• Molecular Biology
• Biochemistry

Background:

• Phosphate is an essential nutrient for all life forms.
• Bacteria possess multiple transport systems for phosphate, each adapted to specific environmental conditions.
• The phosphonate transport system (PhnCDE) in E. coli K-12 is typically non-functional due to a mutation in the phnE gene.

Purpose of the Study:

• To investigate the function of the E. coli phosphonate transport system under conditions where canonical phosphate transporters are absent.
• To determine if the PhnCDE system can transport orthophosphate and support bacterial growth.

Main Methods:

• Utilized an E. coli K-12 triple knockout strain (ΔpitA Δpst Δugp).
• Plated the knockout strain on complex medium with phosphate as the primary phosphorus source.
• Analyzed the reversion of the phnE mutation and characterized the transport kinetics of PhnCDE.

Main Results:

• The phnE mutation reverted in the triple knockout strain when grown on phosphate-rich medium.
• The PhnCDE system demonstrated orthophosphate uptake with kinetics similar to the PitA system.
• PhnCDE-mediated orthophosphate uptake was sufficient to support bacterial growth.
• The Ugp transporter showed no capacity for phosphate uptake.

Conclusions:

• The phosphonate transport system (PhnCDE) is activated in E. coli laboratory strains under selection in rich medium.
• PhnCDE functions as a genuine phosphate transport system, particularly when canonical phosphate uptake pathways (PitA, Pst) are absent.
• This finding expands our understanding of bacterial phosphate acquisition strategies.