The synthesis of carotenoids in strain 2.4.1 of the phototrophic bacterium Rhodobacter sphaeroides is spontaneously turned on and off at a high frequency (10-5 per cell per generation) giving rise alternatively to red (wild type) and green (mutant) clones. The crtD gene is not functional in green mutants as a consequence of the spontaneous addition of a guanosine in a stretch of seven guanosines located in the 5′-terminal coding region of this gene originating a frameshift. All spontaneous wild-type revertants isolated from green mutants had recovered the crtD gene function by loss of one of these reiterated guanosines. The transition Crt+ → Crt- → Crt+, is strain-dependent, since Crt+ clones were not detected in ethyl methane sulphonate (EMS)-induced CrtD- mutants of two other strains of R. sphaeroides (WS22 and RS630) which harbour a recombinant plasmid containing the crtD gene from a spontaneous CrtD- mutant of strain 2.4.1 of R. sphaeroides. © 1992 Springer-Verlag.
|Journal||MGG Molecular & General Genetics|
|Publication status||Published - 1 Mar 1992|
- Carotenoid biosynthesis
- Phase transition
- Phototrophic bacterium
- Rhodobacter sphaeroides
- Spontaneous frameshifts