title: Impairment of O-antigen production confers resistance to grazing in a model amoeba-cyanobacterium predator-prey system.
abstract: The grazing activity of predators on photosynthetic organisms is a major mechanism of mortality and population restructuring in natural environments. Grazing is also one of the primary difficulties in growing cyanobacteria and other microalgae in large, open ponds for the production of biofuels, as contaminants destroy valuable biomass and prevent stable, continuous production of biofuel crops. To address this problem, we have isolated a heterolobosean amoeba, HGG1, that grazes upon unicellular and filamentous freshwater cyanobacterial species. We have established a model predator-prey system using this amoeba and Synechococcus elongatus PCC 7942. Application of amoebae to a library of mutants of S. elongatus led to the identification of a grazer-resistant knockout mutant of the wzm ABC O-antigen transporter gene, SynPCC7942_1126. Mutations in three other genes involved in O-antigen synthesis and transport also prevented the expression of O-antigen and conferred resistance to HGG1. Complementation of these rough mutants returned O-antigen expression and susceptibility to amoebae. Rough mutants are easily identifiable by appearance, are capable of autoflocculation, and do not display growth defects under standard laboratory growth conditions, all of which are desired traits for a biofuel production strain. Thus, preventing the production of O-antigen is a pathway for producing resistance to grazing by certain amoebae.
authors.affiliation: Center for Chronobiology and Division of Biological Sciences, Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA 92093, USA.
authors.forename: Ryan
authors.initials: R
authors.lastname: Simkovsky
authors.forename: Emy F
authors.initials: EF
authors.lastname: Daniels
authors.forename: Karen
authors.initials: K
authors.lastname: Tang
authors.forename: Stacey C
authors.initials: SC
authors.lastname: Huynh
authors.forename: Susan S
authors.initials: SS
authors.lastname: Golden
authors.forename: Bianca
authors.initials: B
authors.lastname: Brahamsha
mesh_terms: D018528:ATP-Binding Cassette Transporters / Q000235:genetics / Q000378:metabolism*; D000656:Amoeba / Q000145:classification / Q000235:genetics / Q000502:physiology*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D001483:Base Sequence; D018533:Biomass; D016054:DNA, Protozoan / Q000737:chemistry / Q000235:genetics; D004591:Electrophoresis, Polyacrylamide Gel; D008858:Microscopy, Phase-Contrast; D008969:Molecular Sequence Data; D009154:Mutation; D019081:O Antigens / Q000096:biosynthesis*; D010802:Phylogeny; D012337:RNA, Ribosomal, 18S / Q000235:genetics; D017422:Sequence Analysis, DNA; D012689:Sequence Homology, Nucleic Acid; D046940:Synechococcus / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism
chemical_list: D018528:ATP-Binding Cassette Transporters; D001426:Bacterial Proteins; D016054:DNA, Protozoan; D019081:O Antigens; D012337:RNA, Ribosomal, 18S