The phosphate transport system in bacteria imports phosphate into the cell even when the concentration of phosphate outside the cell is much lower than the cytoplasmic phosphate concentration. Phosphate import depends on a pH gradient across the membrane (more acidic outside the cell than inside the cell). Phosphate transport is an example of .

Cotranport.

Explanation:

Since  phosphate molecules  were moved  against the  concentration gradients, and H+  moved down the concentration gradient, then this is a co-transport; a form of secondary active transport system that coupled movements of one molecules with another.Because Energy is needed to move phosphate  ions  against its concentration gradient,it is an example of (secondary active transport) .

However because Hydrogen ions  are moved down the concentration gradients  relative to phosphate ions into the bacterial it is symporter ,This is an example of (Facilitated diffusion).

Basically, the energy for the movements of phosphate ions  against the concentration gradient is  obtained from the ionic difference of the influx of hydrogen ions.

The hydrogen ions binds first, and this drive the phospate ions inwrds.Thus phospahte movements is called secondary active transport because apart from ATP,another source of energy was supplied for the transport.