Ecologically important marine cyanobacteria fuel global geochemical cycles: Synechococcus spp. numerically dominate vast areas of the ocean and specific lineages occupy distinct niches. The ability to respond to the key nutrient iron has been hypothesised to determine how Synechococcus can compete for and occupy various ecological niches. However, the molecular mechanism of uptake, storage and regulation of iron acquisition has not been defined in Synechococcus and even less is known in Synechococcus sp. CC9311, a strain from a highly abundant coastal lineage. The response of Synechococcus sp. CC9311 was investigated using a range of physiological measurements, qPCR and global transcriptional analysis that revealed a marked response to iron deplete conditions. 25% of genes were differentially regulated and were enriched in regions of atypical nucleotide usage, so-called genomic islands, predicted to be hot-spots for horizontal gene transfer. These data add weight to the hypothesis that acquisition of specific genomic islands facilitates niche occupancy for marine Synechococcus. The work identified significant up-regulation of a putative iron regulator protein: a CRP-FNR homologue location in a region with key iron uptake genes. Other unique findings include the up-regulation of putative ferrous iron uptake genes, an interesting finding in light of the presumed reliance of ferric iron uptake in sea water. A system for over-expression and purification of CRP1390 in E. coli was optimised to enable its characterisation, with the aim to identify possible DNA and or iron binding capabilities. A large number of genetic constructs were also implemented to inactive crp1390 and other putative regulators (fur orthologues). This study further elucidated the iron stress response of Synechococcus sp. CC9311, highlighted the role of genomic islands in the adaptation process and reiterated the role of iron on this important group of organisms in light of anthropogenic change of the modern ocean.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:589811 |
| Date | January 2013 |
| Creators | Eriksson, Inger Viktoria |
| Publisher | University of Warwick |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://wrap.warwick.ac.uk/58248/ |
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