title: The bacterial carbon-fixing organelle is formed by shell envelopment of preassembled cargo.
abstract: BACKGROUND
  Cyanobacteria play a significant role in the global carbon cycle. In Synechococcuselongatus, the carbon-fixing enzyme ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO) is concentrated into polyhedral, proteinaceous compartments called carboxysomes.
  
  
  RESULTS
  Using live cell fluorescence microscopy, we show that carboxysomes are first detected as small seeds of RuBisCO that colocalize with existing carboxysomes. These seeds contain little or no shell protein, but increase in RuBisCO content over several hours, during which time they are exposed to the solvent. The maturing seed is then enclosed by shell proteins, a rapid process that seals RuBisCO from the cytosol to establish a distinct, solvent-protected microenvironment that is oxidizing relative to the cytosol. These closure events can be spatially and temporally coincident with the appearance of a nascent daughter RuBisCO seed.
  
  
  CONCLUSIONS
  Carboxysomes assemble in a stepwise fashion, inside-to-outside, revealing that cargo is the principle organizer of this compartment's biogenesis. Our observations of the spatial relationship of seeds to previously formed carboxysomes lead us to propose a model for carboxysome replication via sequential fission, polymerization, and encapsulation of their internal cargo.
authors.affiliation: Department of Systems Biology, Harvard Medical School, Boston, Massachusetts, United States of America ; Wyss Institute for Biologically Inspired Engineering, Harvard University, Boston, Massachusetts, United States of America.
authors.forename: Anna H
authors.initials: AH
authors.lastname: Chen
authors.forename: Avi
authors.initials: A
authors.lastname: Robinson-Mosher
authors.forename: David F
authors.initials: DF
authors.lastname: Savage
authors.forename: Pamela A
authors.initials: PA
authors.lastname: Silver
authors.forename: Jessica K
authors.initials: JK
authors.lastname: Polka
mesh_terms: D001426:Bacterial Proteins / Q000378:metabolism; D057486:Carbon Cycle; D002453:Cell Cycle; D049109:Cell Proliferation; D060833:Cellular Microenvironment; D015388:Organelles / Q000378:metabolism*; D010105:Oxygenases / Q000378:metabolism; D021381:Protein Transport; D046940:Synechococcus / Q000166:cytology* / Q000201:enzymology / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D010105:Oxygenases
references.citation: J Gen Microbiol. 1968 Apr;51(2):199-202
references.pmid: 5652095
references.citation: PLoS One. 2008;3(10):e3570
references.pmid: 18974784
references.citation: Science. 2010 Mar 5;327(5970):1258-61
references.pmid: 20203050
references.citation: J Mol Biol. 2010 Feb 12;396(1):105-17
references.pmid: 19925807
references.citation: Methods Mol Biol. 2007;362:155-71
references.pmid: 17417008
references.citation: J Bacteriol. 1969 Mar;97(3):1486-93
references.pmid: 5776533
references.citation: Proc Natl Acad Sci U S A. 2010 Feb 9;107(6):2455-60
references.pmid: 20133749
references.citation: J Biol Chem. 2004 Mar 26;279(13):13044-53
references.pmid: 14722062
references.citation: Annu Rev Biophys. 2010;39:185-205
references.pmid: 20192762
references.citation: J Mol Biol. 2006 Dec 1;364(3):526-35
references.pmid: 17028023
references.citation: PLoS Biol. 2009 Oct;7(10):e1000220
references.pmid: 19841728
references.citation: Annu Rev Microbiol. 2010;64:391-408
references.pmid: 20825353
references.citation: Proc Natl Acad Sci U S A. 2010 Mar 23;107(12):5593-8
references.pmid: 20212111
references.citation: Plant Physiol. 1995 Apr;107(4):1159-1166
references.pmid: 12228422
references.citation: Nat Methods. 2012 Jun 28;9(7):676-82
references.pmid: 22743772
references.citation: Science. 2008 Feb 22;319(5866):1083-6
references.pmid: 18292340
references.citation: Appl Environ Microbiol. 2001 Dec;67(12):5351-61
references.pmid: 11722879
references.citation: Proc Natl Acad Sci U S A. 2010 Apr 20;107(16):7509-14
references.pmid: 20308536
references.citation: Proc Natl Acad Sci U S A. 2012 Jan 10;109(2):478-83
references.pmid: 22184212
references.citation: Science. 2005 Aug 5;309(5736):936-8
references.pmid: 16081736
references.citation: Nat Rev Microbiol. 2012 Oct;10(10):705-15
references.pmid: 22941504
references.citation: Science. 1973 Nov 9;182(4112):584-6
references.pmid: 4355679
references.citation: J Biol Chem. 2013 May 31;288(22):16055-63
references.pmid: 23572529
references.citation: Curr Protoc Mol Biol. 2010 Oct;Chapter 14:Unit14.20
references.pmid: 20890901
references.citation: J Mol Biol. 2007 Sep 21;372(3):764-73
references.pmid: 17669419
references.citation: Nat Methods. 2008 Aug;5(8):695-702
references.pmid: 18641657
references.citation: Proc Natl Acad Sci U S A. 1991 Sep 15;88(18):8184-8
references.pmid: 11607213