title: Specific global responses to N and Fe nutrition in toxic and non-toxic Microcystis aeruginosa.
abstract: The bloom-forming cyanobacteria species Microcystis aeruginosa includes toxic and non-toxic (microcystin-producing) strains. Certain stress conditions stimulate synthesis of microcystin (MCYST) and enhance the binding of the MCYST molecule to proteins. In this quantitative proteomic study, we compared the response of a wild-type toxic strain PCC 7806, an mcyH(-) knockout non-toxic strain, and a naturally occurring non-toxic strain, PCC 7005, after 8 days in low iron (Fe) and nitrogen (N) starvation in order to assess the benefit of MCYST synthesis in non-optimal conditions. Fe limitation increased MCYST synthesis and caused an accumulation of phycobilisome proteins and the ferric iron transporter FutA only in the toxic PCC 7806 but not the non-toxic strains. In N starvation, photosynthetic, C and N metabolism proteins were more abundant in the non-toxic strains, as were chaperones and proteases. Significant interaction between nutrient availability and toxicity existed for thioredoxin peroxidase and several thioredoxin-regulated proteins. We propose a competition of MCYST for binding sites in thioredoxin-regulated proteins during oxidative stress (low Fe) but not in growth-limiting conditions (low N). This then leads to differences in the regulation of C:N metabolism in toxic and non-toxic M. aeruginosa in nutrient-replete and nutrient-limited conditions.
authors.affiliation: School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, NSW, 2052, Australia.
authors.forename: Ralitza
authors.initials: R
authors.lastname: Alexova
authors.affiliation: School of Civil and Environmental Engineering, University of New South Wales, Sydney, NSW, 2052, Australia.
authors.forename: The Cuong
authors.initials: TC
authors.lastname: Dang
authors.affiliation: School of Civil and Environmental Engineering, University of New South Wales, Sydney, NSW, 2052, Australia.|Department of Civil Engineering, Tokyo Institute of Technology, 2-12-1-M1-4 Ookayama, Tokyo, 152-8552, Japan.
authors.forename: Manabu
authors.initials: M
authors.lastname: Fujii
authors.affiliation: Bioanalytical Mass Spectrometry Facility, University of New South Wales, Sydney, NSW, 2052, Australia.
authors.forename: Mark J
authors.initials: MJ
authors.lastname: Raftery
authors.affiliation: School of Civil and Environmental Engineering, University of New South Wales, Sydney, NSW, 2052, Australia.
authors.forename: T David
authors.initials: TD
authors.lastname: Waite
authors.affiliation: School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, NSW, 2052, Australia.|Australian Centre for Astrobiology, University of New South Wales, Sydney, NSW, 2052, Australia.
authors.forename: Belinda C
authors.initials: BC
authors.lastname: Ferrari
authors.affiliation: School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, NSW, 2052, Australia.|Australian Centre for Astrobiology, University of New South Wales, Sydney, NSW, 2052, Australia.
authors.forename: Brett A
authors.initials: BA
authors.lastname: Neilan
mesh_terms: D018528:ATP-Binding Cassette Transporters / Q000378:metabolism; D001665:Binding Sites / Q000502:physiology; D001692:Biological Transport / Q000502:physiology; D055786:Gene Knockout Techniques; D007501:Iron / Q000378:metabolism*; D052998:Microcystins / Q000096:biosynthesis / Q000378:metabolism*; D046931:Microcystis / Q000235:genetics / Q000378:metabolism*; D009584:Nitrogen / Q000378:metabolism*; D018384:Oxidative Stress / Q000502:physiology; D054464:Peroxiredoxins / Q000378:metabolism; D010788:Photosynthesis; D045524:Phycobilisomes / Q000378:metabolism; D040901:Proteomics; D013879:Thioredoxins / Q000378:metabolism
chemical_list: D018528:ATP-Binding Cassette Transporters; D052998:Microcystins; D045524:Phycobilisomes; D013879:Thioredoxins; C078588:microcystin; D007501:Iron; D054464:Peroxiredoxins; D009584:Nitrogen