title: Physiological and Proteomic Responses of Continuous Cultures of Microcystis aeruginosa PCC 7806 to Changes in Iron Bioavailability and Growth Rate.
abstract: The hepatotoxin microcystin (MCYST) is produced by a variety of freshwater cyanobacterial species, including Microcystis aeruginosa Interestingly, MCYST-producing M. aeruginosa strains have been shown to outcompete their nontoxic counterparts under iron-limiting conditions. However, the reasons for this are unclear. Here we examined the proteomic response of M. aeruginosa PCC 7806 continuous cultures under different iron and growth regimes. Iron limitation was correlated with a global reduction in levels of proteins associated with energy metabolism and photosynthesis. These proteomic changes were consistent with physiological observations, including reduced chlorophyll a content and reduced cell size. While levels of MCYST biosynthesis proteins did not fluctuate during the study period, both intra- and extracellular toxin quotas were significantly higher under iron-limiting conditions. Our results support the hypothesis that intracellular MCYST plays a role in protecting the cell against oxidative stress. Further, we propose that extracellular MCYST may act as a signaling molecule, stimulating MCYST production under conditions of iron limitation and enhancing the fitness of bloom populations.
  
  
  
  Microcystin production in water supply reservoirs is a global public health problem. Understanding the ecophysiology of hepatotoxic cyanobacteria, including their responses to the presence of key micronutrient metals such as iron, is central to managing harmful blooms. To our knowledge, this was the first study to examine proteomic and physiological changes occurring in M. aeruginosa continuous cultures under conditions of iron limitation at different growth rates.
authors.affiliation: School of Civil and Environmental Engineering, UNSW, Sydney, NSW, Australia School of Biomolecular and Biosciences, UNSW, Sydney, NSW, Australia.
authors.forename: Anna C Y
authors.initials: AC
authors.lastname: Yeung
authors.affiliation: School of Biomolecular and Biosciences, UNSW, Sydney, NSW, Australia Department of Chemistry, Technische Universität München, Garching, Bayern, Germany.
authors.forename: Paul M
authors.identifier: 0000-0002-8323-5416
authors.initials: PM
authors.lastname: D'Agostino
authors.affiliation: Bioanalytical Mass Spectrometry Facility, UNSW, Sydney, NSW, Australia.
authors.forename: Anne
authors.initials: A
authors.lastname: Poljak
authors.affiliation: School of Civil and Environmental Engineering, UNSW, Sydney, NSW, Australia.
authors.forename: James
authors.initials: J
authors.lastname: McDonald
authors.affiliation: School of Civil and Environmental Engineering, UNSW, Sydney, NSW, Australia.
authors.forename: Mark W
authors.initials: MW
authors.lastname: Bligh
authors.affiliation: School of Civil and Environmental Engineering, UNSW, Sydney, NSW, Australia.
authors.forename: T David
authors.identifier: 0000-0002-5411-3233
authors.initials: TD
authors.lastname: Waite
authors.affiliation: School of Biomolecular and Biosciences, UNSW, Sydney, NSW, Australia b.neilan@unsw.edu.au.
authors.forename: Brett A
authors.initials: BA
authors.lastname: Neilan
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D001682:Biological Availability; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism; D015536:Down-Regulation / Q000187:drug effects; D004734:Energy Metabolism / Q000187:drug effects; D007501:Iron / Q000493:pharmacokinetics / Q000494:pharmacology*; D052998:Microcystins / Q000378:metabolism*; D046931:Microcystis / Q000187:drug effects* / Q000254:growth & development / Q000502:physiology*; D018384:Oxidative Stress / Q000187:drug effects*; D010788:Photosynthesis / Q000187:drug effects; D020543:Proteome; D015854:Up-Regulation / Q000187:drug effects
chemical_list: D001426:Bacterial Proteins; D002352:Carrier Proteins; D052998:Microcystins; D020543:Proteome; C078588:microcystin; D007501:Iron