Benjamin Van Mooy1*, Sonya Dyhrman2
1 Woods Hole Oceanographic Institution, Woods Hole, MA.
Colonies of the cyanbacterium Trichodesmium are responsible for a large fraction of N2 fixation in nutrient-poor, open-ocean ecosystems. Because this nitrogen ultimately fuels primary production in both Trichodesmium and in the broader planktonic community, Trichodesmium thus plays a critical role in their environment. However, in some parts of the ocean, the scarcity of dissolved phosphorus limits rates of Trichodesmium N2 fixation. Trichodesmium colonies employ an arsenal of strategies to mitigate the effects of phosphorus limitation. However, Trichodesmium contain not only Trichodesmium cells but also complex consortia of epibiotic bacteria. The roles these epibionts play in phosphorus acquisition are completely unknown, even though the epibionts might contain as much as half of phosphorus in the colony. The PIs have recently discovered evidence for coordinated phosphorus acquisition, based on quorum sensing, amongst members of these consortia. The PIs posit that this strongly suggests that epibionts play a key role in colonial phosphorus metabolism. To guide their research, they pose four questions about the relative roles Trichodesmium and epibionts in dissolved phosphorus acquisition.
Question 1 - How are phosphorus atoms from phosphate and DOP partitioned between Trichodesmium and their epibionts?
Question 2 - Is the acquisition and partitioning of phosphate and DOP a coordinated effort between Trichodesmium and their epibionts?
Question 3 - What is the role of quorum sensing in affecting the acquisition and partitioning of phosphorus between Trichodesmium and their epibionts?
Question 4 - What is the role of coordination and quorum sensing in affecting physiological phosphorus stress in Trichodesmium and their rates of N2 fixation?