Abstract
The hemolymph metabolome of Mytilus galloprovincialis injected with live Vibrio splendidus bacteria was analyzed by 1H-NMR spectrometry. Changes in spectral hemolymph profiles were already detected after mussel acclimation (3 days at 18 or 25 °C). A significant decrease of succinic acid was accompanied by an increase of most free amino acids, mytilitol, and, to a smaller degree, osmolytes. These metabolic changes are consistent with effective osmoregulation, and the restart of aerobic respiration after the functional anaerobiosis occurred during transport. The injection of Vibrio splendidus in mussels acclimated at 18°C caused a significant decrease of several amino acids, sugars, and unassigned chemical species, more pronounced at 24 than at 12 h postinjection. Correlation heatmaps indicated dynamic metabolic adjustments and the relevance of protein turnover in maintaining the homeostasis during the response to stressful stimuli. This study confirms NMR-based metabolomics as a feasible analytical approach complementary to other omics techniques in the investigation of the functional mussel responses to environmental challenges.
Highlights
Bivalvia comprise many thousands of marine and freshwater species, among which mussels, oysters, and clams are the most relevant in aquaculture (Wijsman et al, 2019)
Once activated by pathogenassociated molecular patterns (PAMPs), the hemocytes circulating in a system of vessels and open sinuses can perform chemotaxis, phagocytosis and oxidative burst, and encapsulation, and quickly release antimicrobial peptides (AMPs), enzymes, and proteins essential as an early defense front line (Gerdol et al, 2018)
We acquired 1H 1D-NMR spectra of Mytilus galloprovincialis hemolymph to investigate the metabolic processes of mussels acclimated in seawater at 18 and 25°C, after 3 h-transport out of water, and mussels immunostimulated at 18°C by injection of 2 × 107 colony-forming units (CFUs) of Vibrio splendidus
Summary
Bivalvia comprise many thousands of marine and freshwater species, among which mussels, oysters, and clams are the most relevant in aquaculture (Wijsman et al, 2019). These bivalves represent interesting models for studying innate immune responses and host–pathogen interactions since they are commonly exposed to microscopic pathogens such as viruses, bacteria, and parasites (Fernández Robledo et al, 2019). The PAMP-induced release of AMPs from granular hemocytes supports pathogen killing in the so-called extracellular networks (ETs) (Poirier et al, 2014; Romero et al, 2020). While adding further layers of complexity, the evolutionary expansion of immune-related genes and the unexpectedly significant phenomenon of gene presence–absence variation in Mytilus
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