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

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posted on 2022-03-29, 01:02 authored by Deepa R. Varkey
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.


Table of Contents

1. Introduction -- 2. Effects of low temperature on tropical and temperate isolates of marine Synechococcus -- 3. Growth physiology and cellular responses of marine Synechococcus isolates to high temperature -- 4. Seasonal variation in the marine cyanobacterial community in Sydney Harbour estuary and the influence of temperature on community structure -- 5. Microbial primary producers of Oceania: molecular characterisation of prokaryotic and eukariotic communities across a range of habitats -- 6. Impact of DNA damaging agents on genome-wide transcriptional profiles in two marine Synechococcus species -- 7. Conclusions and future directions -- Appendix.


Includes bibliographical references Thesis by publication.

Awarding Institution

Macquarie University

Degree Type

Thesis PhD


PhD, Macquarie University, Faculty of Science and Engineering, Department of Chemistry and Biomolecular Sciences

Department, Centre or School

Department of Chemistry and Biomolecular Sciences

Year of Award


Principal Supervisor

Ian Paulsen


Copyright Deepa Ruth Varkey 2016. Copyright disclaimer:




1 online resource (xxi, 192 pages) illustations, maps

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