Stuart, R. K., Dupont, C. L., Johnson, D. A., Paulsen, I. T., Palenik, B.
Coastal Strains of Marine Synechococcus Exhibit Increased Tolerance to Copper Shock and a Distinctive Transcriptional Response Relative to Open Ocean Strains
Appl Environ Microbiol. 2009 Jun 05;
Copper appears to be influencing the distribution and abundance of phytoplankton in marine environments, and cyanobacteria are thought to be the most sensitive of the phytoplankton groups to copper toxicity. Using growth assays, on phylogenetically divergent clades, we found that coastal strains of marine Synechococcus were more tolerant to copper shock than open ocean strains. Global transcriptional response to two levels of copper shock were determined in both a coastal and an open ocean strain of marine Synechococcus using whole genome expression microarrays. Both strains showed an osmoregulatory-like response, perhaps as a result of increasing membrane permeability. This could have implications for marine carbon cycling if copper shock leads to dissolved organic carbon leakage in Synechococcus. The two strains additionally showed a common reduction in photosynthetic-related gene transcripts. Contrastingly, the open ocean strain showed a general stress response whereas the coastal strain exhibited a more specifically oxidative or heavy metal acclimation response, that may be conferring tolerance. In addition, the coastal strain activated more regulatory elements and transporters, many of which are not conserved in other marine Synechococcus strains and may have been acquired by horizontal gene transfer. Thus, tolerance to copper shock in some marine Synechococcus strains may in part be a result of a generally increased ability to sense and respond in a more stress-specific manner.