| Title | Photosynthetic characteristics and diversity of freshwater Synechococcus at two depths during different mixing conditions in a deep oligothrophic lake |
| Abstract | We studied the photosynthetic characteristics and genetic diversity of Synechococcus assemblages at two different light and mixingconditions in a deep oligotrophic lake (Lake Maggiore, Northern Italy). Sampling was performed at the beginning of summer stratification, when the base of the photic zone was isolated by the presence of a shallower thermocline, and during late summer, when the mixing layer extended below the photic zone. Two depths were sampled (15 % and 1 % of surface PAR). To study the diversity of Synechococcus, we used a classical molecular fingerprinting technique (Denaturing Gradient Gel Electrophoresis, DGGE) with ambient samples and sequencing of the prominent bands. The ecotypes selected within the samples from different depths were different in photosynthetic characteristics and grew in a range of nutrient concentrations. The OTUs colonizing different niches in the water column did not show any significant clustering. However, the OTU richness was significantly different at the two depths in spring, reaching the highest values at 15 % of surface PAR. Cluster analysis of DGGE lanes provided evidence of different community compositions between spring and late summer. Sequencing of the most prominent bands showed one spring OTU affiliated to the
Synechococcus subalpine cluster I, with 100% similarity to LM94, MW76B2 and MW15#2 (sensu Crosbie et al. 2003a), not present in late summer. Another OTU present both in spring and late summer showed 100% similarity to MH301, a strain near to subalpine cluster II. Our results support the coexistence of ecotypes in the vertical gradients, rapidly acclimating and performing differently in the microhabitats. |
| Source | Journal of limnology (Testo stamp.) 66 (2), pp. 81–89 |
| Keywords | Freshwater picocyanobacteriaSynechococcus spp.photosynthetic characteristicsgenetic diversityLake Maggiore |
| Journal | Journal of limnology (Testo stamp.) |
| Editor | Istituto per lo Studio degli Ecosistemi., Verbania Pallanza, Italia |
| Year | 2007 |
| Type | Articolo in rivista |
| Authors | Callieri C., Corno G., Caravati E., Galafassi S.(1), Bottinelli M.(2), Bertoni R. |
| Text | 53000 2007 ISI Web of Science WOS 000254013400002 Freshwater picocyanobacteria Synechococcus spp. photosynthetic characteristics genetic diversity Lake Maggiore Photosynthetic characteristics and diversity of freshwater Synechococcus at two depths during different mixing conditions in a deep oligothrophic lake Callieri C., Corno G., Caravati E., Galafassi S. 1 , Bottinelli M. 2 , Bertoni R. 1 Universita Milano Bicocca; 2 Istituto Cantonale di Microbiologia, Bellinzona CH We studied the photosynthetic characteristics and genetic diversity of Synechococcus assemblages at two different light and mixingconditions in a deep oligotrophic lake Lake Maggiore, Northern Italy . Sampling was performed at the beginning of summer stratification, when the base of the photic zone was isolated by the presence of a shallower thermocline, and during late summer, when the mixing layer extended below the photic zone. Two depths were sampled 15 % and 1 % of surface PAR . To study the diversity of Synechococcus, we used a classical molecular fingerprinting technique Denaturing Gradient Gel Electrophoresis, DGGE with ambient samples and sequencing of the prominent bands. The ecotypes selected within the samples from different depths were different in photosynthetic characteristics and grew in a range of nutrient concentrations. The OTUs colonizing different niches in the water column did not show any significant clustering. However, the OTU richness was significantly different at the two depths in spring, reaching the highest values at 15 % of surface PAR. Cluster analysis of DGGE lanes provided evidence of different community compositions between spring and late summer. Sequencing of the most prominent bands showed one spring OTU affiliated to the Synechococcus subalpine cluster I, with 100% similarity to LM94, MW76B2 and MW15#2 sensu Crosbie et al. 2003a , not present in late summer. Another OTU present both in spring and late summer showed 100% similarity to MH301, a strain near to subalpine cluster II. Our results support the coexistence of ecotypes in the vertical gradients, rapidly acclimating and performing differently in the microhabitats. 66 Articolo pubblicato 9_Callieri_et_al_2007_JLimnol.pdf Articolo in rivista Istituto per lo Studio degli Ecosistemi. 1129 5767 Journal of limnology Testo stamp. Journal of limnology Testo stamp. J. limnol. Testo stamp. Journal of limnology. Testo stamp. gianluca.corno CORNO GIANLUCA CARAVATI EMANUELE roberto.bertoni BERTONI ROBERTO cristiana.callieri CALLIERI CRISTIANA TA.P02.014.002 Impatto dei cambiamenti globali sugli ecosistemi acquatici |
