Microenvironments of Trichodesmium colonies

A close-up view on microenvironments within Trichodesmium colonies

The N2-fixing cyanobacterium Trichodesmium forms mm-sized colonies, which host not only a unique microbial community but also chemical conditions that are distinct from the water column surrounding them (i.e., microenvironments). We have used microsensors in combination with stable- and radioisotope incubations to characterize small-scale nutrient conditions and chemical and biological processes within these colony microenvironments, focusing e.g. on O2, pH and H2 microenvironments, nitrogen cycling, as well as iron dissolution and acquisition, both in laboratory cultures and in field-collected colonies. In an on-going collaboration with Prof. Yeala Shaked (IUI), we investigate the biological activity and chemical composition of Trichodesmium colonies in the Gulf of Eilat (Red Sea), with a special interest in the role of dust particles accumulated by these colonies.

• Related publications
• Klawonn, I, Eichner, MJ, Wilson ST, Moradi, N, Thamdrup, B, Kümmel, S, Gehre, M, Khalili, A, Grossart, HP, Karl, DM, Ploug, H (2020): Distinct nitrogen cycling and steep chemical gradients in Trichodesmium colonies. ISME Journal 14(2): 399-412.
• Eichner, M, Thoms, S, Rost, B, Mohr, W, Ahmerkamp, S, Ploug, H, Kuypers, M & de Beer, D (2019). N2 fixation in free-floating filaments of Trichodesmium is higher than in transiently suboxic microenvironments. New Phytologist 222(2): 852-863.
• Eichner, M, Basu, S, Wang, S, de Beer, D, Shaked, Y (2019): Mineral iron dissolution in Trichodesmium colonies: The role of O2 and pH microenvironments. Limnology and Oceanography. https://doi.org/10.1002/lno.11377.
• Eichner, M, Basu, S, Gledhill, M, de Beer, D, Shaked, Y (2019): Hydrogen Dynamics in Trichodesmium Colonies and Their Potential Role in Mineral Iron Acquisition. Frontiers in Microbiology 10, 1565.