Carboxysomes Credit: Anthony Vecchiarelli

Cyanobacteria can take large amounts of carbon dioxide from the environment, and through photosynthesis, create energy for the cell. They are so good at carbon-capture that some fossil-fueled power plants are using tubes packed with cyanobacteria to “scrub” the carbon dioxide from emissions.

Photosynthesis takes place inside each rod-shaped bacterium of Synechococcus elongatus in carboxysomes—enzyme-packed “factories” in the cell that convert the carbon dioxide to energy. The carboxysomes are evenly spaced along the length of the cell so that they don’t compete for resources and when the cell splits, each daughter cell has the correct number of carboxysomes.

Researchers from MCDB’s Vecchiarelli Lab at the University of Michigan and Ducat and Osteryoung labs at Michigan State University with collaborators at NIH recently published a report in eLife that explains how the carboxysomes in each bacterium stay organized along the central axis of the rod-shaped cell. A protein, McdA, was known to oscillate from one end of the cell to the other. The research team has now identified another protein, McdB, that is present on the carboxysomes and binds to the McdA. The McdB seeks out high concentrations of McdA along the nucleoid. This interplay of two proteins allows the self-organization of carboxysomes in the cell.

For a sense of how this works, view this animation produced by The MSU-DOE Plant Research Laboratory

According to the researchers: “We propose that McdA and McdB are a previously unknown class of self-organizing proteins that utilize a Brownian-ratchet mechanism to position carboxysomes in cyanobacteria, rather than a cytoskeletal system. These results have broader implications for understanding spatial organization of protein mega-complexes and organelles in bacteria.”

In addition to the research article, this work was also featured in an eLife Digest.

Find both at: eLife 2018;7:e39723 DOI: 10.7554/eLife.39723

Authors of the report are: Joshua S MacCready, Life Sciences Fellow in the Vecchiarelli Lab, formerly a graduate student in the Ducat Lab at MSU; Pusparanee Hakim, a graduate student in the Vecchiarelli Lab; Eric J Young, MSU student; Longhua Hu, NIH; Jian Liu, NIH; Katherine W Osteryoung, Professor, MSU; Anthony G Vecchiarelli, Assistant Professor, MCDB; Daniel C Ducat, Assistant Professor, MSU