Connecting thermal physiology and latitudinal niche partitioning in marine Synechococcus

• Published in: The ISME Journal Vol. 8; no. 6; pp. 1221 - 1236
• Main Authors: Pittera, Justine, Humily, Florian, Thorel, Maxine, Grulois, Daphné, Garczarek, Laurence, Six, Christophe
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 01-06-2014; Nature Publishing Group
• Subjects: 631/158/2446/2447; 631/326/41/1969; Animal biology; Atlantic Ocean; Biomedical and Life Sciences; Cold Temperature; Cyanobacteria; Ecology; Ecotypes; Equator; Evolutionary Biology; High temperature; Inactivation; Latitude; Life Sciences; Microbial Ecology; Microbial Genetics and Genomics; Microbiology; Ocean, Atmosphere; Original; original-article; Oxidative stress; Photosynthesis; Phylogeny; Polar fronts; Sciences of the Universe; Seawater - microbiology; Synechococcus; Synechococcus - classification; Synechococcus - genetics; Synechococcus - isolation & purification; Temperature; Temperature gradients; temperature; adaptation; marine cyanobacteria; ecotype
• ISSN: 1751-7362; 1751-7370
• DOI: 10.1038/ismej.2013.228

Marine
Synechococcus
cyanobacteria constitute a monophyletic group that displays a wide latitudinal distribution, ranging from the equator to the polar fronts. Whether these organisms are all physiologically adapted to stand a large temperature gradient or stenotherms with narrow growth temperature ranges has so far remained unexplored. We submitted a panel of six strains, isolated along a gradient of latitude in the North Atlantic Ocean, to long- and short-term variations of temperature. Upon a downward shift of temperature, the strains showed strikingly distinct resistance, seemingly related to their latitude of isolation, with tropical strains collapsing while northern strains were capable of growing. This behaviour was associated to differential photosynthetic performances. In the tropical strains, the rapid photosystem II inactivation and the decrease of the antioxydant β-carotene relative to chl
a
suggested a strong induction of oxidative stress. These different responses were related to the thermal
preferenda
of the strains. The northern strains could grow at 10 °C while the other strains preferred higher temperatures. In addition, we pointed out a correspondence between strain isolation temperature and phylogeny. In particular, clades I and IV laboratory strains were all collected in the coldest waters of the distribution area of marine
Synechococus
. We, however, show that clade I
Synechococcus
exhibit different levels of adaptation, which apparently reflect their location on the latitudinal temperature gradient. This study reveals the existence of lineages of marine
Synechococcus
physiologically specialised in different thermal niches, therefore suggesting the existence of temperature ecotypes within the marine
Synechococcus
radiation.