Energy transduction and solute transport in streptococci.

Metabolic energy in lactic streptococci can be generated by substrate level phosphorylation and by efflux of end-products in symport with protons. During growth on lactose or glucose Streptococcus cremoris maintains a high proton motive force and phosphate potential. Both energy intermediates dissipate rapidly when the energy supply stops. In the initial phase of starvation the internal phosphoenolpyruvate (PEP) pool increases rapidly and this enables the organism for a prolonged period during starvation to accumulate the energy source via a PEP-dependent uptake system.