Cell- and genome size responses to different temperatures in haptophytes

In recent years, environmental concerns and global temperature increase has attracted a wide interest. Global temperature has increased in the recent years, and will continue to do so in the near future. How organisms, especially those that are important for the ecosystem, i.e. primary producers, such as algae, react to this, is of interest to get a better understanding of. The relationship between cell size and temperature has been an interesting field of study since the Bergmann-rule was introduced. Though, this was meant to describe endotherm organisms, the rule has often been applied to ectotherms, also giving rise to the Temperature-Size rule (TSR). The cell size and temperature has been shown to often correlate negatively. It has also been shown to exist a relationship between cell size and genome size, being positively correlated. The direct relationship between genome size and temperature is therefore an interesting study. To study this, two different species, Prymnesium kappa and Calyptrosphaera sp, was used as study organisms and cultivated on different temperatures, 11oC and 19oC, for over a year. Genome size was estimated using flow cytometry (FCM). Other parameters, such as cell size, RNA amount, protein amount and stoichiometry (C:N:P-ratios) was also analysed. The algal cells were also examined using electron microscopy, and DNA sequencing and k-mer analysis was used for an additional genome size estimation. The genome sizes estimated using FCM indicated that a change in genome size had occurred for both species, but the 11oC treated cultures of Prymnesium kappa showed a strong increase in genome size. The other independent analysis also suggested that a change had occurred between the two temperature treatments, indicating that temperature change can induce visible changes, not only in the genome, but in other parameters, as those mentioned above, as well. From all the acquired results from this study, temperature has shown to have a great impact on the cells and can, and have shown to, induce a change in genome size, where the genome size is negatively correlated with temperature. Key words: Genome, Flow Cytometry, Temperature, Algae, DN