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Kraft, C. E.

Publications and source records attributed to Kraft, C. E..

2 recordsLinked to original sources
bioRxiv2026

A ratiometric biochemical framework reveals strain-specific metabolic allocation strategies in brook trout liver

Brook trout (Salvelinus fontinalis) exhibit strain-level variation in growth performance, environmental tolerance, and survival, yet the biochemical mechanisms underlying these differences remain poorly understood. We developed and applied a ratiometric biochemical framework integrating the pentose-phosphate pathway (PPP) and glutathione metabolism to characterize strain-specific hepatic metabolic organization in brook trout. Five strains reared under standardized conditions differed significantly in hepatic soluble protein density, glutathione pool size, total NADP(H) concentration, and activities of glucose-6-phosphate dehydrogenase (G6PDH), glutathione reductase (GR), and transketolase (TKT). These differences were not uniformly coordinated across pathways, demonstrating that metabolic phenotype cannot be inferred from individual biomarkers alone. Derived ratios describing oxidative-to-non-oxidative PPP capacity (G6PDH/TKT) and glutathione buffering relative to recycling capacity ((GSH+GSSG)/GR) resolved distinct patterns of metabolic allocation among strains. Despite shared ancestry, the Temiscamie (TEM) strain and its domestic x TEM hybrid (TXD) exhibited markedly divergent metabolic phenotypes, demonstrating that closely related strains can differ substantially in hepatic metabolic organization. Together, these findings identify relative allocation among interconnected metabolic pathways as an axis of physiologic diversity and establish a ratiometric approach for comparing metabolic organization across populations and species. Graphical abstractHepatic metabolic phenotypes of brook trout strains were characterized by integrating pentose phosphate pathway enzyme capacities, glutathione metabolism, NADP(H) availability, and soluble protein into a ratiometric framework. Ratios distinguish investment in oxidative versus non-oxidative PPP capacity (G6PDH/TKT), antioxidant buffering versus glutathione recycling capacity (total glutathione/GR), and hepatic protein density (soluble protein/liver mass), revealing distinct metabolic organization among strains. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=88 SRC="FIGDIR/small/743818v1_ufig1.gif" ALT="Figure 1"> View larger version (25K): org.highwire.dtl.DTLVardef@dc1b21org.highwire.dtl.DTLVardef@79528borg.highwire.dtl.DTLVardef@11a2805org.highwire.dtl.DTLVardef@398be9_HPS_FORMAT_FIGEXP M_FIG C_FIG HighlightsO_LIA ratiometric framework was developed to characterize hepatic metabolic organization in brook trout C_LIO_LIGlutathione buffering and recycling capacity distinguish alternative redox phenotypes C_LIO_LIInvestment in oxidative and non-oxidative PPP capacity varies independently among strains C_LIO_LIG6PDH/TKT and total glutathione (GSH+GSSG)/GR reveal distinct metabolic phenotypes C_LIO_LIRatiometric indices provide a framework for interpreting redox metabolism and carbon allocation C_LI

biochemistry↗
bioRxiv2025

The allelopathic vitamin B1 antagonist bacimethrin impacts microbial gene expression in a hypereutrophic watershed dominated by cyanobacterial blooms

Freshwater cyanobacterial harmful algal blooms (cyanoHABs), often dominated by Aphanizomenon, Dolichospermum, and Microcystis, are intensifying in eutrophic watersheds globally. A potential control on bacterioplankton dynamics in these systems is the availability of the essential metabolic cofactor thiamin (vitamin B1) and presence of the allelopathic thiamin antagonist, bacimethrin, that competitively inhibits thiamin-requiring enzymes. We examined dissolved concentrations of thiamin chemical congeners and bacimethrin, 16S-amplicon based microbiome compositions, prokaryotic mRNA-based metatranscriptomes, and reference genomes in hypereutrophic Upper Klamath Basin before and during seasonal cyanoHABs. Our objective was to connect bacterioplankton community compositions and gene expression patterns with thiamin congener and bacimethrin availability under different cyanoHAB conditions. Bacimethrin was present in all samples at nearly equimolar concentrations to the thiamin precursor, HMP, suggesting that similar mechanisms influence the availability of both compounds. Additionally, bacimethrin concentrations were positively correlated with cyanoHAB species abundance (cells mL-1) and the expression of microbial thiamin biosynthesis genes. Samples with high cyanoHAB abundances displayed elevated transcription of genes for thiamin biosynthesis, the pentose phosphate pathway, and photosynthesis. Bacterioplankton unable to synthesize thiamin and thus vulnerable to bacimethrin allelopathy, such as Limnohabitans spp., showed reduced gene expression when cyanoHAB abundances were high. Reference genomes of cyanoHAB and many picocyanobacteria strains contained complete thiamin biosynthesis gene pathways, implicating these taxa as major thiamin sources. These results suggest that bacimethrin provides a competitive advantage to bacterioplankton that do not require exogenous vitamin B1 by eliminating the risk of bacimethrin uptake with vitamin B1 transporters, potentially facilitating cyanoHAB dominance in Upper Klamath Basin and broader eutrophic watersheds.

microbiology↗