Proton symporter that senses osmotic shifts and responds by importing osmolytes such as proline, glycine betaine, stachydrine, pipecolic acid, ectoine and taurine. It is both an osmosensor and an osmoregulator which is available to participate early in the bacterial osmoregulatory response (By similarity). Belongs to the major facilitator superfamily. Metabolite:H+ Symporter (MHS) family (TC 2.A.1.6) family.