Changes in Population Age-Structure Obscure the Temperature-Size Rule in Marine Cyanobacteria

The temperature-size Rule (TSR) states that there is a negative relationship between ambient temperature and body size. This rule has been independently evaluated for different phases of the life cycle in multicellular eukaryotes, but mostly for the average population in unicellular organisms. We acclimated two model marine cyanobacterial strains (Prochlorococcus marinus MIT9301 and Synechococcus sp. RS9907) to a gradient of temperatures and measured the changes in population age-structure and cell size along their division cycle. Both strains displayed temperature-dependent diel changes in cell size, and as a result, the relationship between temperature and average cell size varied along the day. We computed the mean cell size of new-born cells in order to test the prediction of the TSR on a single-growth stage. Our work reconciles previous inconsistent results when testing the TSR on unicellular organisms, and shows that when a single-growth stage is considered the predicted negative response to temperature is revealed.

Palacio, A. S., Cabello, A. M., García, F. C., Labban, A., Morán, X. A. G., Garczarek, L., … López-Urrutia, Á. (2020). Changes in Population Age-Structure Obscure the Temperature-Size Rule in Marine Cyanobacteria. Frontiers in Microbiology, 11. doi:10.3389/fmicb.2020.02059

We thank Laura Díaz-Pérez and Tamara Megan Huete-Stauffer for their technical support. This article is contribution number 1075 from AZTI (Marine Research). Funding. We are grateful to the Spanish Ministry of Economy and Competitiveness (MINECO) for supporting LA-S’s Ramón y Cajal research contract (RYC-2012-11404), AP’s FPI Ph.D. fellowship (BES2015076149) as well as the TECCAM project (CTM2014-58564-R) and to the ANR for the CINNAMON project (ANR-17-CE2-0014-01).

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