Temporal and spatial distributions of marine Synechococcus in the Southern California Bight assessed by hybridization to bead-arrays

摘要

Marine Synechococcus diversity has been previously described using multi-locus gene sequence phylogenies and the identification of distinct clades. Synechococcus from Clades Ⅰ, Ⅱ, Ⅲ, and Ⅳ and from sub-clades within Clades I and IV were enumerated from environmental samples by developing a hybridization assay to liquid bead-arrays (Luminex). Oligonucleotide probes targeting a gene encoding a subunit of RNA polymerase (rpoC1) were used simultaneously in multiplexed assays to track Synechococcus diversity from a Pacific Ocean coastal monitoring site and along a coastal to open-ocean transect in the Southern California Bight. The Luminex assay demonstrated that Synechococcus from Clades Ⅰ and Ⅳ were the dominant types at the coastal site throughout the year. Synechococcus from Clades Ⅱ and Ⅲ were not detected except during the late summer or early winter. Within the dominant Clades I and Ⅳ rpoCi-defmed sub-clades of Synechococcus showed distinct spatial distributions along the coastal to open-ocean transect, coinciding with changes in the nitricline, thermocline, and fluorescence (chlorophyll) maximum depths. In coastal waters, Synechococcus targeted by 2 sub-clade Ⅳ probes were dominant at the surface, whereas 2 sub-clade Ⅰ probes and a third sub-cladeⅣ probe had increased signals in deeper water near the fluorescence maximum. In mesotrophic waters, this third sub-clade Ⅳprobe dominated at the fluorescence maximum (depth of 50 to 70 m), whereas all other sub-clade probes were below detection limits. The differing distributions of sub-clades within the dominant Synechococcus clades indicate that the sub-clades likely have adapted to distinct ecological niches found within the Southern California Bight.