Seminar Details

Mutual quest for mineral and dust Fe by Trichodesmium and associated bacteria

Date

21/06/2018

Lecturers

Dr. Subhajit Basu - The Hebrew University of Jerusalem; and The Interuniversity Institute for Marine Sciences in Eilat

Abstract

We studied the interactions between natural colonies of the ecologically significant nitrogen fixing marine cynaobacterium Trichodesmium and their associated bacteria during mineral and dust-iron utilization. Dust is a significant potential iron source to phytoplankton in the open ocean, but its biological use is restricted by its low solubility. Many marine bacteria have the genetic knowhow of excreting siderophores, strong iron chelators capable of solublizing mineral iron. We hypothesize that bacteria associated with Trichodesmium play a role in solubilizing dust-iron by releasing siderophores. These dissolved iron complexes may be accessible or inaccessible to Trichodesmium, raising the possibility of mutualistic and/or competitive relationships. Assaying cultured bacteria isolated from Red Sea Trichodesmium, we found that most isolates are indeed capable of producing siderophores. Using advanced separation and identification techniques we detected and partially quantified large array of siderophores naturally occurring in Red Sea and Arabian Sea Trichodesmium blooms. We examined the differential ability of the colony members to acquire iron from minerals by incubating fresh natural populations with radiolabelled Ferrihydrite and separating Trichodesmium from its associated bacteria. By adding active and inactive siderophores (extracted from bacterial isolates) to paired experiments, we probed for the effect of siderophores on Ferrihydrite solubilization and uptake. The added siderophores enhanced Ferrihydrite solubilization and iron uptake by both Trichodesmiumand its associated bacteria, suggesting that their quest for dust-iron is mutual.

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