Name of plankton: SAR11

Where sample was found: Bermuda Atlantic Time-series Study (BATS) site, 80m

Project: Microbial Observatory

Photo credit: Rachel Parsons, BIOS

What role do these organisms play in the ecosystem: SAR11 are heterotrophic bacteria that dominate the euphotic zone of the ocean comprising up to 40% of the total bacterioplankton population. They are known as oligotrophs or scavengers that feed on dissolved organic carbon and nitrogen and are important in the marine carbon and nitrogen cycles.

Interesting facts: The photo shows total bacterioplankton on the left in blue stained with DAPI. The photo also shows SAR11 in the middle targeted using Fluorescent in-situ hybridization with oligonucleotide probes labeled with Cy3. The right hand side shows the two images overlaid with SAR11 positive cells shown in pink.

SAR11 has one of the smallest number of open reading frames of any free living organism, but it still has metabolic pathways for all 20 amino acids and most co-factors. Its genome has been streamlined, thereby reducing the amount of energy required for cell replication.