Bacteria Patterns Aid Carbon Fixation

Harvard Medical School researchers have discovered that the organelles responsible for carbon fixation within cyanobacteria organize themselves in predictable patterns—a finding that could help researchers engineer more efficient designer bacteria.

The study found that cyanobacteria produce carboxysomes—organelles instrumental in the process of carbon fixation—in quantities proportional to the length of their longest axis and subsequently align these organelles uniformly along the axis, according to David F. Savage, HMS research fellow and co-lead author of the study.

The structural precision of the carboxysomes’ positioning—which is not often found within single-celled organisms—increases the efficiency of the cyanobacteria’s carbon fixation, the process through which gaseous carbon is converted into organic fuel molecules, according to Savage.

Autotrophs, such as cyanobacteria, produce complex organic molecules from simpler inorganic compounds using solar energy through the process of photosynthesis.

The HMS researchers said that scientists hope to use cyanobacteria as a model organism to create genetically-modified designer bacteria capable of producing biofuels. Greater carbon fixation efficiency in cyanobacteria would increase the efficiency of biofuel production in these bacteria, according to the research team.

“The bigger vision is one of sustainability,” said Pamela A. Silver, co-author of the study and professor of systems biology at HMS. “Ideally you could have an organism that you could program to make anything you wanted using only sunlight—you could use it, for example, to provide energy for the third world.”

Designer cyanobacteria could also provide cheaper ways to produce biofuel, Silver added.

The study represents “an interesting example in which you’re doing applied research and then you make some interesting basic fact-findings also,” Savage said.

The HMS researchers said that they plan to focus next on strains of cyanobacteria that use an engineered lipid synthesis pathway that allows the bacteria to directly secrete biofuels into growth medium.

The study was funded by the U.S. Army Research Office through a grant seeking to engineer cyanobacteria that produces biofuel molecules, such as hydrogen and biodiesel.

The study’s results were published in the Mar. 5 issue of “Science.”