AME 45:107-113 (2006)  -  doi:10.3354/ame045107

ABSTRACT: Low nucleic acid (LNA) bacterioplankton (sorted by flow cytometry) were characterised in surface water samples along a meridional transect from 48°N to 40°S across the Atlantic Ocean. The LNA bacterioplankton abundance and metabolic activity, assessed by their ³⁵S-methionine uptake rate, were similar along the transect, representing 36 ± 6 and 36 ± 11% of total bacterioplankton, respectively. Fluorescence in situ hybridisation analysis of the flow-sorted cells revealed that the LNA bacterioplankton population was dominated (59 ± 4%) by and contained virtually all the identifiable SAR11 clade cells throughout the Atlantic Ocean. Therefore, the present study provides ecological characterisation of this flow-sorted group and suggests both phylogenetic and functional constancy of the LNA bacterioplankton at the basin-scale.

KEY WORDS: Flow cytometry sorting · Cell metabolic activity · SAR11 clade · CARD-FISH · Radioactive tracer labelling · Atlantic Ocean