Co-occurrence of Fe and P stress in natural populations of the marine diazotroph <i>Trichodesmium</i>

Abstract

<p><strong>Abstract.</strong> <i>Trichodesmium</i> is a globally important marine microbe that provides fixed nitrogen to otherwise N limited ecosystems. In nature, nitrogen fixation is likely regulated by iron or phosphate availability, but the extent and interaction of these controls is unclear. From metaproteomics analyses using established protein biomarkers for iron and phosphate stress, we found that co-stress is the norm rather than the exception for field <i>Trichodesmium</i> colonies. Counter-intuitively, the nitrogenase enzyme was most abundant under co-stress, consistent with the idea that <i>Trichodesmium</i> has a specific physiological state under nutrient co-stress. Organic nitrogen uptake was observed to occur simultaneously with nitrogen fixation. Quantification of the phosphate ABC transporter PstC combined with a cellular model of nutrient uptake suggested that <i>Trichodesmium</i> is confronted by the biophysical limits of membrane space and diffusion rates for iron and phosphate acquisition. Colony formation may benefit nutrient acquisition from particulate and organic nutrient sources, alleviating these pressures. The results indicate that to predict the behavior of <i>Trichodesmium</i>, we must consider multiple nutrients simultaneously across biogeochemical contexts.</p>

Projected expansion of Trichodesmium’s geographical distribution and increase in growth potential in response to climate change

“…We did not consider the potential role of phosphorus limitation in our model. Diazotrophs are reported to be iron limited in the Pacific and Indian Ocean, and phosphorus limited (Misumi et al., 2014) or phosphorus–iron co‐stressed (Held et al, 2020; Mills, Ridame, Davey, La Roche, & Geider, 2004) in the Atlantic Ocean. A reduction in dust deposition could have major implications for the phosphorus pool as well as iron.…”

Mechanisms and heterogeneity of mineral use by natural colonies of the cyanobacteriumTrichodesmium

“…Compared to population-level metaproteomes from this location, which each integrated 50-100 colonies, proteome depth for the low biomass single colonies was lower but sufficient for characterizing overall colony function ( Fig. S6) 18 Fig. 1B and Fig.…”

“…There were indications that the particles altered nitrogen metabolism more generally, for instance through enrichment of nitrogen assimilation proteins glutamine synthetase (p = 0.008), spermidine synthase (p = 0.005), and a urea transporter (p = 0.02) (see Fig. S7) 18 . Because nitrogen fixation is a critical process, Trichodesmium may distribute iron to nitrogenase at a steady rate, while altering the activity of other systems in response to the particles.…”

“…3D). IdiA is often used as a biomarker of iron stress because it is responsive to/more abundant in low Fe conditions 18,19,23 . Due to its specificity for Fe(III), IdiA is likely involved in direct acquisition of iron from the particles.…”

Diversity of cyanobacteria in shipwrecks in the shallow water of New Calabar River, Nigeria

“…Surface associated microorganisms play important roles in numerous critical marine processes, including organic matter remineralization nutrient regeneration and element cycling. 12 Surfaces once submerged in marine water are rapidly colonized 13 and subsequent biofilm formation follows a sequence of chemical and biological occurrences.…”