Mechanisms of trace metal assimilation in marine Roseobacters

Conference: 2014 Goldschmidt Conference - Sacramento, CA
Poster Number: 236
Session: 17e: Oceans and Atmosphere: Trace elements, microbes, and biogeochemical cycles in the ocean environment.
Presentation Day: Wednesday 6/11/2014
Time: 14:00 - 17:00

TITLE: Mechanisms of trace metal assimilation in marine Roseobacters

ABSTRACT: In the marine environment, Mn, Fe, Co, Ni, Cu, and Zn are arguably the most important bioactive trace metals. The are present as cofactors in enzymes, such as those involved in nitrate assimilation, and thus can indirectly influence the cycling of macronutrients in marine systems. The Roseobacter clade is an abundant group of marine bacteria with a global distribution. They have been isolated from diverse environments and appear to be well adapted to dynamic conditions and changing nutrient availability. The Roseobacter clade has been shown to be influential in the marine carbon, nitrogen, and sulfur cycles, but little is known as to how they influence the cyling of trace metals. Here we present case studies from bioinformatic genome mining and genetic analyses that point to molecular mechanisms of how the Roseobacter clade might influence the cycling of metals in their environments. We surveyed 42 marine Roseobacter genomes for the presence of uptake systemsfor oxidized, reduced, and chelated metal species. Systems for theacquisition of inorganic Mn, Fe, Co, Ni, Cu, and Zn were identified using sequence homology searches. Specific metal-chelates were assigned to predicted transporters and related components using sequence homology searches, genome neighborhood analysis, and Markov sequence clustering. We also report an unexpected putative role for tripartite ATP-independent periplasmic transporters in assimilation of metal chelates, particularly siderophores. Further, we describe the functional characterization of an outer membrane receptor required for heme uptake in a particular Roseobacterstrain, Ruegeria sp. TM1040, by insertional inactivation of a predicted TonB dependent transporter.Collectively, these findings refine the our knowledge of the specific metal compounds encountered and potentially utilized by microbes in marine environments.