Trichodesmium metaproteome samples across three ocean regions

The diazotroph Trichodesmium is an important contributor to marine dinitrogen (N2) fixation, supplying so-called new N to phytoplankton in typically N-limited ocean regions. Identifying how iron (Fe) and phosphorus (P) influence Trichodesmium activity and biogeography is an ongoing area of study, where predicting patterns of resource stress is complicated in part by the uncertain bioavailability of organically complexed Fe and P. Here, a comparison of 26 metaproteomes from picked Trichodesmium colonies identified significantly different patterns between three ocean regions: the western tropical South Pacific, the western North Atlantic, and the North Pacific Subtropical Gyre. Trichodesmium metaproteomes across these regions significantly differed in KEGG submodule signals, and vector fitting showed that dissolved Fe, phosphate, and temperature significantly correlated with regional proteome patterns. Populations in the western tropical South Pacific appeared to modulate their proteomes in response to both Fe and P stress, including a comparatively low relative abundance of the N2 fixation marker protein, NifH. Significant increases in the relative abundance of both Fe and P stress marker proteins previously validated in culture studies suggested that Trichodesmium populations in the western North Atlantic and North Pacific were P-stressed and Fe-stressed, respectively. These patterns recapitulate established regional serial and co-limitation patterns of resource stress on phytoplankton communities. Evaluating community stress patterns may therefore predict resource controls on diazotroph biogeography. These data highlight how Trichodesmium modulates its metabolism in the field and provide an opportunity to more accurately constrain controls on Trichodesmium biogeography and N2 fixation.