Sarah Brown

The presence of a 'selfish' substrate uptake mechanism has only recently been identified in bacteria in the surface waters of the ocean. This mechanism allows bacteria to bind, hydrolyze, and transport large fragments of polysaccharides across the outer membrane and into the periplasm with minimal loss of hydrolysis products to other members of the community. The presence and abundance of selfish bacteria may affect the flow of carbon in the ocean by changing the quantity and quality of organic carbon available to other members of the microbial community. This study aimed to investigate the presence and abundance of selfish bacteria with depth, as previous studies have focused primarily on the distribution of selfish bacteria in surface waters. We examined the abundance of selfish bacteria in surface waters (2.5 m) and at 300 m at three locations in the North Atlantic Ocean. Selfish uptake of fluorescently-labeled polysaccharides was very rapid, occurring within 15 minutes of substrate addition. Selfish bacteria were present and capable of selfish uptake of four distinct polysaccharides at depths as deep as 300 m.