Streptococcus faecalis proton gradients and tetracycline transport

Area of Science:

• Microbiology
• Molecular Biology
• Biochemistry

Background:

• Chlortetracycline is an antibiotic with known transport mechanisms in bacteria.
• Bacterial cell membrane transport is often energy-dependent and influenced by electrochemical gradients.
• Streptococcus faecalis is a relevant model organism for studying bacterial transport.

Purpose of the Study:

• To investigate the energy dependence of chlortetracycline transport in Streptococcus faecalis.
• To determine the specific electrochemical gradient driving chlortetracycline uptake.
• To elucidate the mechanism of chlortetracycline accumulation.

Main Methods:

• Measuring chlortetracycline transport rates and accumulation levels in Streptococcus faecalis.
• Utilizing glucose to manipulate cellular energy levels.
• Employing ionophores to alter the proton gradient and transmembrane electrical potential.
• Quantitatively measuring transmembrane pH difference (delta pH) and transmembrane electrical potential (delta psi).

Main Results:

• Chlortetracycline transport is energy-dependent, enhanced by glucose in energy-depleted cells.
• Transport rates are modulated by ionophores affecting the proton gradient.
• Antibiotic transport is solely dependent on delta pH, not delta psi.
• A linear correlation exists between delta pH and tetracycline electrochemical potential.

Conclusions:

• Chlortetracycline transport in Streptococcus faecalis is driven by the proton motive force, specifically the delta pH component.
• The accumulation mechanism involves the symport of protons with an anionic form of chlortetracycline.
• Understanding this transport mechanism is crucial for antibiotic efficacy and resistance studies.