Discrimination of Two Phycoerythrin-Pigment Types of Synechococcus and Their Seasonal Succession in the Uwa Sea

Abstract

We identified phycoerythrin-pigment phenotypes of Synechococcus strains in samples obtained from the Uwa Sea, and investigated the seasonal changes in the pigment-type composition of the Synechococcus community in this sea from January 2001 to March 2002. Two Synechococcus strains (UT01 and UT02) with different flow cytometric signatures were isolated by sorting and subsequent culturing. Excitation spectra showed that these two strains possessed different ratios of phycourobilin (PUB) to phycoerythrobilin (PEB). Flow cytometric signatures of the two types were also different; UT01 showed a higher green to red fluorescence ratio than UT02. The ranges of green to red fluorescence intensity of the strains did not overlap, though the strains were cultured under various light intensities (7-160 mE m -2 s -1 ). In seawater samples, we could divide Synechococcus into lowerand higher-PUB types based on the ratio. There were two peaks of total Synechococcus abundance in June (2.8´10 5 cells ml -1 ) and August (1.6´10 5 cells ml -1 ) in the upper layer at a depth of 0 to 15 m. Major types during these two peaks were different; the higher-PUB type contributed 75.6% to the total Synechococcus community in June, and the lower-PUB type, 58.6% in August. This is the first report which describes the seasonal succession of two phycoerythrin-pigment types of Synechococcus in a coastal sea.

Distribution of prokaryotic picophytoplankton from Seto Inland Sea to the Kuroshio region, with special reference to ‘Kyucho’ events

“…In contrast to Prochlorococcus, the high-PUB type of Synechococcus actively grows in Uchiumi Bay (Katano et al 2005, Katano & Nakano 2006 and has been detected throughout the year (Katano et al 2004). However, the fluorescence properties of high-PUB-type cells were different from those in the northern part of the Bungo Channel.…”

“…We were also able to determine that Synechococcus in the bay consisted of a different type of PUB:PEB cells (Katano et al 2004, Katano & Nakano 2006. The composition of these 2 types significantly fluctuated during the summer season, when the Kyucho frequently occurs (Katano et al 2004). Thus, this fluctuation appears to be related to the occurrence of the Kyucho.…”

“…The composition of the PE pigment in Uchiumi Bay, a body of water in the Bungo Channel, fluctuated significantly (Katano et al 2004, Katano & Nakano 2006. In 2001, there were 2 peaks of Synechococcus abundance in June and August (Katano et al 2004).…”

“…In 2001, there were 2 peaks of Synechococcus abundance in June and August (Katano et al 2004). Analysis of the PE-pigment-type composition using single laser flow cytometry showed that the high-PUB type contributed 75% in June, but the contribution decreased to 40% in August (Katano et al 2004).…”

“…In 2001, there were 2 peaks of Synechococcus abundance in June and August (Katano et al 2004). Analysis of the PE-pigment-type composition using single laser flow cytometry showed that the high-PUB type contributed 75% in June, but the contribution decreased to 40% in August (Katano et al 2004). In 2003, the contribution of the high-PUB type estimated with dual laser flow cytometry increased from 38% in May to 75% in July (Katano & Nakano 2006).…”