In Vivo Monitoring of Cytosolic pH Using the Ratiometric pH Sensor pHluorin

Cytosolic pH (pHcyt) is a key factor controlling cell fate. The genetically encoded pH-sensor pHluorin has proven highly valuable for studies on pHcyt in many living organisms. pHluorin displays a bimodal excitation spectrum with peaks at 395 nm and 475 nm, which is dependent on pH. Here we describe two different protocols for determining pHcyt in the soil-borne fungal pathogen Fusarium oxysporum, based either on population or single-cell analysis.