The free guanidine and polyamine pools of bivalve mollusks in relation to their ecology

Key metabolites in tissue extracts of Elliptio complanata identified using (1)H nuclear magnetic resonance spectroscopy

We used (1)H nuclear magnetic resonance spectroscopy to describe key metabolites of the polar metabolome of the freshwater mussel, Elliptio complanata. Principal components analysis documented variability across tissue types and river of origin in mussels collected from two rivers in North Carolina (USA). Muscle, digestive gland, mantle and gill tissues yielded identifiable but overlapping metabolic profiles. Variation in digestive gland metabolic profiles between the two mussel collection sites was characterized by differences in mono- and disaccharides. Variation in mantle tissue metabolomes appeared to be associated with sex. Nuclear magnetic resonance spectroscopy is a sensitive means to detect metabolites in the tissues of E. complanata and holds promise as a tool for the investigation of freshwater mussel health and physiology.

Application of NMR-based metabolomics for environmental assessment in the Great Lakes using zebra mussel (Dreissena polymorpha)

Zebra mussel, Dreissena polymorpha, in the Great Lakes is being monitored as a bio-indicator organism for environmental health effects by the National Oceanic and Atmospheric Administration's Mussel Watch program. In order to monitor the environmental effects of industrial pollution on the ecosystem, invasive zebra mussels were collected from four stations-three inner harbor sites (LMMB4, LMMB1, and LMMB) in Milwaukee Estuary, and one reference site (LMMB5) in Lake Michigan, Wisconsin. Nuclear magnetic resonance (NMR)-based metabolomics was used to evaluate the metabolic profiles of the mussels from these four sites. The objective was to observe whether there were differences in metabolite profiles between impacted sites and the reference site; and if there were metabolic profile differences among the impacted sites. Principal component analyses indicated there was no significant difference between two impacted sites: north Milwaukee harbor (LMMB and LMMB4) and the LMMB5 reference site. However, significant metabolic differences were observed between the impacted site on the south Milwaukee harbor (LMMB1) and the LMMB5 reference site, a finding that correlates with preliminary sediment toxicity results. A total of 26 altered metabolites (including two unidentified peaks) were successfully identified in a comparison of zebra mussels from the LMMB1 site and LMMB5 reference site. The application of both uni- and multivariate analysis not only confirmed the variability of altered metabolites but also ensured that these metabolites were identified via unbiased analysis. This study has demonstrated the feasibility of the NMR-based metabolomics approach to assess whole-body metabolomics of zebra mussels to study the physiological impact of toxicant exposure at field sites.

Changes of polyamine pattern in digestive glands of mussel Mytilus galloprovincialis under exposure to cadmium

Polyamines, in particular spermidine and spermine, have been identified as important antioxidants, highly induced by oxidative stress in a variety of organisms. However, little is known about changes in polyamine content of metal-stressed marine organisms. In the present study, mussels (Mytilus galloprovincialis) were experimentally exposed to 25 μg/L Cd(2+) or 100 μg/L Cd(2+) for up to 15 days. Cd(2+) was progressively accumulated in mussel tissues, leading to a characteristic oxidative-stress status. Free putrescine (PUT) production was noticeably induced in response to Cd(2+) at day 5 and then declined. In contrast, free spermidine (SPD) content was gradually reduced, whereas the concentration of free spermine (SPM) increased. In combination, these changes led to a 69% or 88% reduction in the ratio of (SPD+SPM)/PUT at day 5, dependent on the Cd(2+) concentration used, which subsequently followed an upward trend in values, albeit not reaching those of controls. Conjugated polyamines constantly increased, in particular conjugated spermidine and spermine, tagging along with metallothionein production. Acetylated polyamines showed a diverse profile of changes, but their content was generally kept at low levels throughout the exposure period. Collectively, our results suggest that certain polyamine compounds could play a significant role in the tolerance of mussels against Cd(2+)-mediated stress, and that the ratio (SPD+SPM)/PUT could be a good indicator of the metal-stress status.

The protein synthesis machinery operates at the same expense in eurythermal and cold stenothermal pectinids

Translationally active cell-free systems from gills of the Antarctic scallop Adamussium colbecki and the European scallop Aequipecten opercularis were developed, characterised, and optimised for an analysis of translational capacity. The aim was to determine the energetic cost of protein synthesis in the in vitro cell-free system by directly measuring the required energy equivalents in the lysates. Protein synthesis rate in assays conducted with lysates of A. colbecki (1.029+/-0.061 micromol Phe min(-1) at 15 degrees C; Phe=phenylalanine) were higher compared with lysates of A. opercularis (0.087+/-0.013 micromol Phe min(-1) at 15 degrees C and 0.156+/-0.023 micromol Phe min(-1) at 25 degrees C). This can in part be attributed to the naturally occurring higher RNA content in lysates of A. colbecki (0.883+/-0.037 mg RNA mL(-1) lysate) compared with A. opercularis (0.468+/-0.013 mg RNA mL(-1) lysate). There was no significant difference in the energetic costs of protein synthesis in cell-free systems of gill lysates of the cold stenothermal A. colbecki with 4.3+/-0.7 energy equivalents per peptide bond formed and the eurythermal A. opercularis with 5.6+/-0.6 energy equivalents, indicating that there are no differences in the efficiency of the translation machinery. The energetic costs specified for protein synthesis correspond with the generally accepted theoretical value of four energy equivalents per peptide bond formed, especially in gill lysates of A. colbecki, whereas the value for gill lysates of A. opercularis was slightly higher.