Why do alpha-cyanobacteria with form 1A RuBisCO dominate aquatic habitats worldwide? (CYANORUB)
Lead Research Organisation:
University of Warwick
Department Name: School of Life Sciences
Abstract
RuBisCO is one of the most abundant enzymes on Earth. Virtually all food webs depend on it to supply fixed carbon. In aerobic
environments, RuBisCO struggles to distinguish efficiently between CO2 and O2. To compensate, many photosynthetic organisms
have developed CO2-concentrating mechanisms (CCMs) to increase the [CO2] around the RuBisCO active site. In cyanobacteria,
carboxysomes represent one such CCM, of which two independent forms exist: alpha and beta. This ancient photoautotrophic
lineage has succeeded in colonizing habitats worldwide, being primary producers of great ecological importance. Amongst them,
cells of the genera Prochlorococcus and Synechococcus, the two most abundant photosynthetic taxa on Earth, dominate oceanic
ecosystems. These marine picocyanobacteria possess a form IA RuBisCO and alpha-carboxysomes (so-called alpha-cyanobacteria).
The remainder of the cyanobacterial radiation was thought to possess beta-carboxysomes and a form IB RuBisCO (beta-
cyanobacteria), including freshwater unicellular and filamentous bloom-forming taxa comprising model organisms used in
laboratories worldwide e.g. Synechococcus elongatus and Synechocystis. However, recently I have isolated and sequenced the
genomes of many new unicellular freshwater picocyanobacteria that are phylogenetically much closer to their marine counterparts
and which also possess a form IA RuBisCO and alpha-carboxysomes. Moreover, these organisms have been detected in high
abundance in freshwater lakes and reservoirs worldwide. Thus, alpha-cyanobacteria dominate all aquatic systems. CYANORUB seeks
to address why this is the case. We hypothesize that alpha-cyanobacteria dominate large, temporally stable water masses,
characterized by well-buffered pHs and relatively slow changes in carbonate chemistry. CYANORUB will be crucial for accurately
predicting the biosphere's response to changing CO2, pH and carbonate chemistry and has biotechnological applications aimed at
improving plant growth.
environments, RuBisCO struggles to distinguish efficiently between CO2 and O2. To compensate, many photosynthetic organisms
have developed CO2-concentrating mechanisms (CCMs) to increase the [CO2] around the RuBisCO active site. In cyanobacteria,
carboxysomes represent one such CCM, of which two independent forms exist: alpha and beta. This ancient photoautotrophic
lineage has succeeded in colonizing habitats worldwide, being primary producers of great ecological importance. Amongst them,
cells of the genera Prochlorococcus and Synechococcus, the two most abundant photosynthetic taxa on Earth, dominate oceanic
ecosystems. These marine picocyanobacteria possess a form IA RuBisCO and alpha-carboxysomes (so-called alpha-cyanobacteria).
The remainder of the cyanobacterial radiation was thought to possess beta-carboxysomes and a form IB RuBisCO (beta-
cyanobacteria), including freshwater unicellular and filamentous bloom-forming taxa comprising model organisms used in
laboratories worldwide e.g. Synechococcus elongatus and Synechocystis. However, recently I have isolated and sequenced the
genomes of many new unicellular freshwater picocyanobacteria that are phylogenetically much closer to their marine counterparts
and which also possess a form IA RuBisCO and alpha-carboxysomes. Moreover, these organisms have been detected in high
abundance in freshwater lakes and reservoirs worldwide. Thus, alpha-cyanobacteria dominate all aquatic systems. CYANORUB seeks
to address why this is the case. We hypothesize that alpha-cyanobacteria dominate large, temporally stable water masses,
characterized by well-buffered pHs and relatively slow changes in carbonate chemistry. CYANORUB will be crucial for accurately
predicting the biosphere's response to changing CO2, pH and carbonate chemistry and has biotechnological applications aimed at
improving plant growth.