Glycogenandcompatiblesolutesarethemajorpolymericandsolublecarbohydratesincyanobacteria
and functionasenergyreservesandosmoprotectants,respectively.Glycogensynthasenullmutants
(glgA-IglgA-II) wereconstructedinthecyanobacterium Synechococcus sp. strainPCC7002.Under
standardconditionsthedoublemutantproducednoglycogenandmoresolublesugars.Whengrown
under hypersalineconditions,the glgA-I glgA-II mutantaccumulated1.8-foldmoresolublesugars
(sucrose andglucosylglycer-(ol/ate))thanWT,andthesecellsspontaneouslyexcretedsolublesugars
into themediumathighlevelswithouttheneedforadditionaltransporters.Anaverageof27%more
solublesugarswasreleasedfromthe glgA-IglgA-II mutantthanWTbyhypo-osmoticshock.
Extracellularvesiclesbuddingfromtheoutermembranewereobservedbytransmissionelectron
microscopyin glgA-IglgA-II cells grownunderhypersalineconditions.The glgA-IglgA-II mutantserves
as astartingpointfordevelopingcellfactoriesforphotosyntheticproductionandexcretionofsugars