The CO2-concentrating mechanism of Synechococcus WH5701 is composed of native and horizontally-acquired components

Photosynth Res. 2011 Sep;109(1-3):59-72. doi: 10.1007/s11120-011-9641-5. Epub 2011 Mar 8.


The cyanobacterial CO(2)-concentrating mechanism (CCM) is an effective adaptation that increases the carbon dioxide (CO(2)) concentration around the primary photosynthetic enzyme Ribulose-1,5-bisphosphate Carboxylase/Oxygenase (RuBisCO). α-Cyanobacteria (those containing Form1-A RuBisCO within cso-type α-carboxysomes) have a limited CCM composed of a small number of Ci-transporters whereas β-cyanobacteria (those species containing Form-1B RuBisCO within ccm-type β-carboxysomes) exhibit a more diverse CCM with a greater variety in Ci-transporter complement and regulation. In the coastal species Synechococcus sp. WH5701 (α-cyanobacteria), the minimal α-cyanobacterial CCM has been supplemented with β-cyanobacterial Ci transporters through the process of horizontal gene transfer (HGT). These transporters are transcriptionally regulated in response to external Ci-depletion however this change in transcript abundance is not correlated with a physiological induction. WH5701 exhibits identical physiological responses grown at 4% CO(2) (K (1/2) ≈ 31 μM Ci) and after induction with 0.04% CO(2) (K (1/2) ≈ 29 μM Ci). Insensitivity to external Ci concentration is an unusual characteristic of the WH5701 CCM which is a result of evolution by HGT. Our bioinformatic and physiological data support the hypothesis that WH5701 represents a clade of α-cyanobacterial species in transition from the marine/oligotrophic environment to a coastal/freshwater environment.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Bacterial Proteins / genetics*
  • Bacterial Proteins / metabolism
  • Biological Evolution
  • Biological Transport
  • Carbon / metabolism*
  • Carbon Dioxide / metabolism*
  • Carbon Dioxide / pharmacology
  • Computational Biology
  • Cyanobacteria / classification
  • Cyanobacteria / genetics
  • Fresh Water / microbiology
  • Gene Expression Regulation, Bacterial
  • Gene Transfer, Horizontal / genetics*
  • Genomic Islands
  • Photosynthesis
  • Phylogeny
  • RNA, Bacterial / genetics
  • Ribulose-Bisphosphate Carboxylase / genetics
  • Ribulose-Bisphosphate Carboxylase / metabolism
  • Ribulosephosphates / metabolism
  • Seawater / microbiology
  • Sequence Alignment
  • Synechococcus / classification
  • Synechococcus / genetics
  • Synechococcus / metabolism
  • Synechococcus / physiology*


  • Bacterial Proteins
  • RNA, Bacterial
  • Ribulosephosphates
  • Carbon Dioxide
  • ribulose-1,5 diphosphate
  • Carbon
  • Ribulose-Bisphosphate Carboxylase