Hi! I have never worked with prokaryotes (except those occasionally contaminating my cell cultures), but I may have a suggestion for you: Both, pH and redox status can be reliably determined by specific, ratiometric or nonratiometric fluorescent dyes. A good choice of such dyes is available from Molecular Probes (Invitrogen, Life Sciences). Most are extensively tested in eucaryotes, but in principle they should also work in prokaryotes. In most cases you will have the choice to use a fluorescence microscope or a spectrofluorimeter (which may be preferrable in small procaryotes). Good luck! 

Thanks both, but i was thinking if it is correct if I wash and then destroy the cell wall of my microorganism to measure the potential redox and pH of this aqueous solution with the respective probes.