Thread by @CellfOrganized

New preprint from the Vecchiarelli lab!

"Cyanobacterial growth and morphology are influenced by carboxysome positioning and temperature"

Work from Rees Rillema @Rees7942 and Joshua MacCready

biorxiv.org/content/10.110…

Like Plants, cyanobacteria use the enzyme RuBisCO to fix CO2 into organic carbon molecules. Unlike plants, cyanobacteria evolved an organelle called the carboxysome - a protein compartment that encapsulates and concentrates RuBisCO along with its CO2 substrate.

In cyanobacterium Synechococcus elongatus PCC7942, the McdAB system distributes carboxysomes along the cell length. McdAB systems are widespread in beta-cyanobacteria. But it is still unclear what role carboxysome positioning plays with respect to cellular physiology??

Here, we show that a failure to distribute carboxysomes in S. elongatus leads to a temperature-dependent decrease in cell growth rate, changes in cell morphology, and a significant reduction in cellular levels of RuBisCO.

When grown at 40degC, McdAB mutant cells look and grow like wild-type. At 30degC, McdAB mutants elongate and divide asymmetrically, but with similar growth rates.

Unexpectedly, we found that even wild-type S. elongatus elongates at the cool but environmentally-relevant growth temperature of 20°C! We THINK this is the first example of COLD STRESS eliciting a cell elongation phenotype in bacteria. Thoughts anyone?

At 20degC, McdAB mutants exhibit slower growth rates and do not elongate as well as wild-type. Finally!

We propose that carboxysome positioning by the McdAB system functions to maintain carbon-fixation efficiency of RuBisCO by preventing carboxysome aggregation, which is particularly important at cooler temperatures where rod-shaped cyanobacteria adopt a filamentous morphology.

Alternative hypothesis! 20degC is around the temperature in which protistan predators graze on S. elongatus. Therefore, S. elongatus may “sense” grazing season via temperature changes. Filamentous bacteria are harder to eat.

This paper even has a shout out to #Caulobacter! We would love to hear comments and suggestions!

@threadreaderapp plz unroll