The photocycle of bacteriorhodopsin (bR) reconstituted into dimyristoylphosphatidylcholine vesicles was investigated with transient visible absorption spectroscopy. The measured time-resolved difference spectra indicated that two substates of the M intermediate with almost the same absorption maximum were observed in the gel state, whereas the spectrum of M showed a splitting into an early and a late component shifted by approximately 15 nm in the liquid crystalline phase, suggesting disassembly of bR molecules induces remarkable structural changes around the retinal pocket of the late M intermediate responsible for switching protein conformation from a proton release form to a proton uptake form.