title: Altered carbohydrate metabolism in glycogen synthase mutants of Synechococcus sp. strain PCC 7002: Cell factories for soluble sugars.
abstract: Glycogen and compatible solutes are the major polymeric and soluble carbohydrates in cyanobacteria and function as energy reserves and osmoprotectants, respectively. Glycogen synthase null mutants (glgA-I glgA-II) were constructed in the cyanobacterium Synechococcus sp. strain PCC 7002. Under standard conditions the double mutant produced no glycogen and more soluble sugars. When grown under hypersaline conditions, the glgA-I glgA-II mutant accumulated 1.8-fold more soluble sugars (sucrose and glucosylglycer-(ol/ate)) than WT, and these cells spontaneously excreted soluble sugars into the medium at high levels without the need for additional transporters. An average of 27% more soluble sugars was released from the glgA-I glgA-II mutant than WT by hypo-osmotic shock. Extracellular vesicles budding from the outer membrane were observed by transmission electron microscopy in glgA-I glgA-II cells grown under hypersaline conditions. The glgA-I glgA-II mutant serves as a starting point for developing cell factories for photosynthetic production and excretion of sugars.
authors.affiliation: Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, PA 16802, USA.
authors.forename: Yu
authors.initials: Y
authors.lastname: Xu
authors.forename: L Tiago
authors.initials: LT
authors.lastname: Guerra
authors.forename: Zhongkui
authors.initials: Z
authors.lastname: Li
authors.forename: Marcus
authors.initials: M
authors.lastname: Ludwig
authors.forename: G Charles
authors.initials: GC
authors.lastname: Dismukes
authors.forename: Donald A
authors.initials: DA
authors.lastname: Bryant
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics*; D005947:Glucose / Q000096:biosynthesis* / Q000235:genetics; D006006:Glycogen Synthase / Q000235:genetics*; D009154:Mutation; D009997:Osmotic Pressure; D010788:Photosynthesis; D013395:Sucrose / Q000378:metabolism*; D046940:Synechococcus / Q000235:genetics / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D013395:Sucrose; D006006:Glycogen Synthase; D005947:Glucose