Roseobacter biogeography: distributions of an ecologically important marine bacterial clade

Alison Buchan, University of Tennessee

Abstract

The Roseobacter clade is a broadly distributed and biogeochemically relevant group of heterotrophic marine bacteria.  This large lineage is well defined by 16S rRNA gene phylogeny and high abundances in diverse marine habitats have been revealed in gene surveys.   Roseobacter abundance tends to be highest in coastal environments where they can account for upward of 30% of bacterioplankton communities, but its members also contribute significantly to open ocean microbial assemblages.  Recently, we have been able to delineate several subgroups within this clade, representing the most prevalent sequences in environmental inventories.  Some of these subgroups lack cultured isolates.  Thus, we developed quantitative tools (qPCR assays) to monitor three specific subpopulations for detailed studies of their distributions and dynamics over temporal and spatial scales.  I will discuss how application of these qPCR assays to samples collected from the Chesapeake Bay, a North Atlantic Ocean transect, and a fjord mesocosm study provide insight into the distinct ecological niches of these uncultured groups.