Differential temperature adaptation in marine Synechococcus lineages: ecological distribution, molecular and physiological acclimation mechanisms

Marine picocyanobacteria are abundant photosynthetic prokaryotes contributing significantly to global primary production and nutrient cycling. The genus Synechococcus is ubiquitous in the marine environment. Their habitat ranges from the polar regions to the equator and mesotrophic to oligotrophic environments. Such a widespread occurrence across a broad array of environmental conditions is facilitated by the diverse genetic complement of lineages of Synechococcus. This work explores the influence of temperature on the lineages of Synechococcus which occupy different temperature niches. Responses and acclimation strategies employed by individual lineages were examined with gene expression analyses including global cellular proteomics and transcriptomics. Comparisons of growth physiology at different temperature conditions provide evidence for the specific temperature preferences of lineages. This is the first study to compare temperature acclimation responses across multiple lineages of marine Synechococcus. The acclimation responses to temperature involved the light harvesting complex, photosynthesis, membrane fluidity and protein synthesis with distinct differences between lineages. This is the first study to determine the composition and structure of the Synechococcus community across different temperature regimes in regions around Australia were studied using various phylogenetic markers. Distinctive spatial and temporal partitioning of lineages is observed with temperature as a potential key factor shaping the population. Other co-varying factors such as nutrients and mixing were also determined to influence the partitioning of lineages. This work provides insights into temperature acclimation and the distinct niche preferences of marine Synechococcus lineages. The differences in their distribution, growth and acclimation suggest that changes in temperature regimes can significantly alter Synechococcus community structure. Culture based studies in addition to environmental distribution provide valuable information for predictive models. As significant contributors to primary production and biogeochemical cycling, it is important to understand the influence of temperature and other factors on their diversity and distribution for better monitoring of ecosystem health.