sentence: In sunlit environments where sulfide is present , some cyanobacteria can use sulfide as the electron donor to PS I in the absence of oxygen generation ( Cohen et al ., 1975a , 1975b ; Padan , 1979 ; Padan and Cohen 1982 ; Castenholz et al ., 1990 ; 1991 ) , enabling PS II ‐ independent photoassimilation of CO with the same efficiency as oxygenic photosynthesis ( Oren et al ., 1977 ; Oren and Padan , 1978 ) .