Biology subjects

Suffridge, C.

Publications and source records attributed to Suffridge, C..

3 recordsLinked to original sources

bioRxiv2026

Thiamine availability and acquisition differ between natural and controlled environments

Thiamine Deficiency Complex (TDC) is a reproductive disorder that affects recruitment of diverse salmonine populations globally. Typical symptoms include behavioral and neurological abnormalities and high offspring mortality. TDC is common in hatcheries that rear salmonines obtained from wild populations, and symptoms are mitigated by thiamine treatment. However, no studies have quantified thiamine concentrations in wild embryos. Here, we evaluated whether fertilized eggs and/or embryos may acquire thiamine from natural sources (e.g., biotic breakdown products and diet) during development. Lake trout (Salvelinus namaycush) gametes were obtained from feral adults in Lake Champlain and fertilized eggs were grouped by family with paired rearing under natural (Lake Champlain) and artificial (controlled laboratory) conditions. Average thiamine concentrations were similar between lake-reared and laboratory-reared fish prior to hatch; however, lake-reared fish experienced significant increases in thiamine concentrations at and after hatching compared to previous stages and compared to laboratory-reared fish; laboratory-reared fish experienced no increases in thiamine concentrations. Water samples revealed an abundance of thiamine precursors and byproducts in the natural environment, which may serve as sources of thiamine for developing embryos. These results demonstrate that salmonine embryos can acquire thiamine from natural sources during development, which may mitigate effects of TDC.

ecology↗

bioRxiv2025

Harmful algal bloom species Microcystis aeruginosa releases thiamin antivitamins to suppress competitors

In environmental ecosystems, vitamin concentrations are often exceedingly low (1, 2) and auxotrophy, or reliance on exogenous vitamin or vitamin precursors, is widespread (3-5). We show here that the widespread harmful algal bloom (HAB) species Microcystis aeruginosa, threatening freshwater aquatic ecosystems globally, releases a complex mixture of thiamin antivitamins, including bacimethrin and methoxythiamin, which induce thiamin deficiency in the benign model green alga Chlamydomonas reinhardtii. Putative biosynthetic genes for bacimethrin were upregulated in M. aeruginosa when grown in co-culture resulting in greater production of bacimethrin. Bacimethrin, methoxythiamin, oxidized forms of thiamin and methoxythiamin, and a novel structural homolog of bacimethrin were all found at elevated levels in the co-culture exometabolome extracts and were all inhibitory to the growth of C. reinhardtii individually at very low concentrations and as a mixture in culture medium extracts. The thiamin-requiring mutant C. reinhardtii, CC-25, was much more sensitive to bacimethrin and methoxythiamin than the wildtype. Thiamin addition largely rescued the inhibitory effects of exposure to antivitamins in both the wildtype and mutant strain. Finally, we determined that bacimethrin is present in aquatic environments and is elevated during Microcystis blooms. Thus, allelopathic suppression of competitors, particularly those that are auxotrophic for thiamin, by M. aeruginosa via the production of antivitamins in environments where thiamin availability is low, could help this species to become dominant and form blooms.

microbiology↗

bioRxiv2021

SAR11 Cells Rely on Enzyme Multifunctionality to Transport and Metabolize a Range of Polyamine Compounds

In the ocean surface layer and cell culture, the polyamine transport protein PotD of SAR11 bacteria is often one of the most abundant proteins detected. Polyamines are organic cations produced by all living organisms and are thought to be an important component of dissolved organic matter (DOM) produced in planktonic ecosystems. We hypothesized that SAR11 cells transport and metabolize multiple polyamines and use them as sources of carbon and nitrogen. Metabolic footprinting and fingerprinting were used to measure the uptake of five polyamine compounds (putrescine, cadaverine, agmatine, norspermidine, and spermidine) in two SAR11 strains that represent the majority of SAR11 cells in the surface ocean environment, Ca. Pelagibacter st. HTCC7211 and C. P. ubique st. HTCC1062. Both strains transported all five polyamines and concentrated them to micromolar or millimolar intracellular concentrations. Both strains could use most of the polyamines to meet their nitrogen requirements, but we did not find evidence of use as carbon sources. We propose potABCD transports cadaverine, agmatine, and norspermidine, in addition to its usual substrates of spermidine and putrescine, and that spermidine synthase, speE, is reversible, catalyzing the breakdown of spermidine and norspermidine, in addition to its usual biosynthetic role. These findings provide support for the hypothesis that enzyme multifunctionality enables streamlined cells in planktonic ecosystems to increase the range of DOM compounds they oxidize. ImportanceGenome streamlining in SAR11 bacterioplankton has resulted in a small repertoire of genes, yet paradoxically they consume a substantial fraction of primary production in the oceans. Enzyme multifunctionality is hypothesized to be an adaptation that increases the range of organic compounds oxidized by cells in environments where selection favors genome minimization. We provide experimental support for this hypothesis by demonstrating that SAR11 cells use multiple polyamine compounds and propose that a small set of multifunctional genes catalyze this metabolism. We also report polyamine uptake rates can exceed metabolism, resulting in high intracellular concentrations of these nitrogen-rich compounds and an increase in cell size. Increases in cytoplasmic solute concentrations during transient episodes of high nutrient exposure has previously been observed in SAR11 cells and may be a feature of their strategy for maximizing the share of labile DOM acquired when in competition with other cell types.

microbiology↗