Biology subjects

Rowland, E.

Publications and source records attributed to Rowland, E..

5 recordsLinked to original sources

bioRxiv2026

Novel connections between B-vitamins and microbial communities along biogeochemical gradients in a large temperate estuary

As B-vitamins are organic cofactors required by prokaryotic and eukaryotic planktonic cells, their availability impacts aquatic microbial communities and associated biogeochemistry. Contrary to inorganic nutrients, measurements of B-vitamins from brackish systems are scarce and relationships between B-vitamins and plankton composition in estuaries are unclear, limiting our understanding of estuary biology in general as well as how B-vitamins are distributed and dispersed in marine systems. Here, we quantify multiple B-vitamins and their vitamers in particulate and dissolved phases, and characterize microbial community composition, across fresh to polyhaline zones of the Neuse River Estuary (NRE), North Carolina, USA. We uncover elevated concentrations of B-vitamins within the mid-estuary, Chlorophyll a maximum along with a unique suite of dissolved B-vitamin associated with sporadic surges in pico- and microplankton populations. The dynamics of both dissolved and particulate B-vitamin concentrations in space and time were striking - from subpicomolar to high picomolar levels observed and strong short-term (weeks) variability. We find notable autochtonous B-vitamin production in the estuary, but we expect the ability of the system to deliver these micronutrients to the ocean will depend on flushing as well as changes in microbial community. We identify vitamin B1, B12, psB12 (pseudocobalamin), and B3 as key explanatory variables for change in prokaryotic and eukaryotic NRE plankton, providing new evidence of B-vitamin influence upon estuarine plankton community composition. Our work reveals new complexities in B-vitamin production and consumption within zones of estuaries while underscoring these micronutrients as key drivers of microbial plankton composition.

ecology↗

bioRxiv2025

Elemental allocation to molecular drivers of biogeochemistry in the Southern Ocean

Metabolic processes underpinning ocean biogeochemistry are powered by molecular machines, proteins, that require various elements to function. Yet, the allocation of elements to these proteins, and subsequent implications for biogeochemical processes, remain poorly characterized. Here we integrate elemental measurements with metaproteomics to quantitatively examine elemental use in Southern Ocean microbial proteins and metabolic processes. We demonstrate that iron availability influences elemental allocation, including decreased iron allocation to photosynthesis and compensatory incorporation of non-iron metals into metalloproteins under iron scarcity. Manganese was primarily allocated to photosynthesis in iron-replete conditions, and reallocated to other metabolic roles under low iron. Photosystem I:II protein mass ratios impacted both iron and manganese allocation, and appeared to be driven by iron availability. Approximately half of biogenic copper was found in plastocyanin, likely substituting for iron-containing cytochromes in photosynthesis. Moreover, biogenic nitrogen to phosphorus ratios were decoupled from ribosomal abundance, contrary to prevailing assumptions about ribosomal influence on stoichiometric regulation in the ocean. Instead, our results suggest that community composition and intracellular storage are important regulators of N:P in the Southern Ocean. Together, our findings identify key molecular mechanisms that modulate elemental demand and limitation, and provide a foundation for quantitatively connecting molecular measurements with biogeochemical models.

microbiology↗

bioRxiv2025

Superoxide dismutases shape manganese stoichiometry in Southern Ocean diatoms

Elemental stoichiometry of biomass is a focal point that connects different biogeochemical cycles. Yet, the mechanistic underpinnings of elemental stoichiometry are poorly quantified in many cases. We combined targeted and untargeted metaproteomics, Bayesian statistical modelling, and geochemical measurements to quantify the contribution of specific proteins to metal stoichiometry in natural populations of Southern Ocean diatoms. Our analyses indicate that a substantial amount of non-photosynthetic manganese (Mn) in diatoms in an Antarctic polynya can be attributed to superoxide dismutases ([~]0.7 {micro}mol Mn: mol Carbon; [~]20% of the total cellular Mn quota). We then used cultures and proteomic profiling of the key polar diatom Fragilariopsis cylindrus to identify environmental controls on superoxide dismutases, and discovered that iron concentration has little influence on the abundance of two Mn superoxide dismutases, while Mn limitation induces the depletion of these Mn superoxide dismutases and an accompanying increase of nickel superoxide dismutase. Overall, we combined metaproteomic approaches to quantify proteomic composition and connected these measurements to metal-to-carbon ratios and their responses to metal availability. Because metal quotas are key parameters in some biogeochemical models, our approach provides a direct mechanism for informing ecosystem-scale models with molecular measurements.

microbiology↗

bioRxiv2024

Seasonal patterns in b-vitamins and cobalamin co-limitation in the Northwest Atlantic

B-vitamins are important co-enzymes that have long been hypothesized to play key roles in marine ecosystems. However, environmental measurements remain scarce, which limits our understanding of their potential impact. Here, we present mass spectrometry-based measurements of b-vitamins (B1, B2, B3, B5, B6, B12) and related vitamers along a transect in the Northwest Atlantic Ocean, in both particulate phase and dissolved in seawater, seasonally over 5 years, and couple this with targeted investigations of the impact of B12 (cobalamin) on phytoplankton growth. We show that these metabolites are present at femto to pico-molar concentrations and demonstrate that season explains most variance in particulate phase b-vitamins but not dissolved, offering further evidence that metabolite inventories in these two phases are often decoupled. We find correlations between particulate organic carbon with particulate B1 and B3, and between chlorophyll a and particulate B2 and DMB in fall but not spring, indicating unique seasonal drivers of vitamin inventories. Of all measured vitamins, only cobalamin was enriched in the particulate over dissolved phase, predominantly in spring. We documented nitrogen and cobalamin co-limitation of phytoplankton growth during spring bloom decline, when dissolved cobalamin is seemingly drawn down, but not during fall, when dissolved cobalamin concentrations remain elevated. These seasonal differences may be underpinned by the increased importance of cobalamin remodeling and recycling during the fall. This study provides insights into the absolute concentrations, stoichiometry, and variability of b-vitamins in the ocean and offers evidence that cobalamin exerts seasonally-varying controls on Northwest Atlantic marine ecosystems.

microbiology↗

bioRxiv2024

Pseudocobalamin production and use in Synechococcus cultures and communities

Cobalamin influences marine microbial communities because an exogenous source is required by most eukaryotic phytoplankton, and demand can exceed supply. Pseudocobalamin is a cobalamin analog that is produced and used by most cyanobacteria but is not directly available to eukaryotic phytoplankton. Some microbes can remodel pseudocobalamin into cobalamin, but a scarcity of pseudocobalamin measurements impedes our ability to evaluate its importance for marine cobalamin production. Here, we perform simultaneous measurements of pseudocobalamin and methionine synthase (MetH), the key protein that uses it as a co-factor, in Synechococcus cultures and communities. In Synechococcus sp. WH8102, pseudocobalamin quota decreases in low temperature (17 {degrees}C) and low N:P, while MetH did not. Pseudocobalamin and MetH quotas were influenced by culture methods and growth phase. Despite the variability present in cultures, we found a comparably consistent quota of 300 {+/-} 100 pseudocobalamin molecules per cyanobacterial cell in the Northwest Atlantic Ocean, suggesting that cyanobacterial cell counts may be sufficient to estimate pseudocobalamin inventories in this region. This work offers insights into cellular pseudocobalamin metabolism, and the environmental and physiological conditions that may influence it, and provides environmental measurements to further our understanding of when and how pseudocobalamin can influence marine microbial communities.

microbiology↗