Posts Tagged 'pathogens'

Low pH reduced survival of the oyster Crassostrea gigas exposed to the Ostreid herpesvirus 1 by altering the metabolic response of the host

Highlights

  • The susceptibility of Crassostrea gigas to OsHV-1 increased at pH 7.8 in comparison to pH 8.1
  • The amount of OsHV-1 in oyster tissues was the same at both pH, suggesting the role of host metabolic response in differential survival
  • A lower activity of SOD and a basal activity of iNOS at pH 7.8, in comparison to pH 8.1, may have impaired the defence of oysters to OsHV-1 explaining the lower survival

Abstract

Environmental change in the marine realm has been accompanied by emerging diseases as new pathogens evolve to take advantage of hosts weakened by environmental stress. Here we investigated how an exposure to reduced seawater pH influenced the response of the oyster Crassostrea gigas to an infection by the Ostreid herpesvirus type I (OsHV-1). Oysters were acclimated at pH 8.1 or pH 7.8 and then exposed to OsHV-1. Their survival was monitored and oyster tissues were sampled for biochemical analyses. The survival of oysters exposed to OsHV-1 at pH 7.8 was lower (33.5%) than that of their counterparts at pH 8.1 (44.8%) whereas levels of OsHV-1 DNA were similar. Energetic reserves, fatty acid composition and prostaglandin levels in oyster did not vary consistently with pH, infection or their interactions. However, there was a reduction in the activities of superoxide dismutase (SOD) and nitric oxide synthase (iNOS) in oysters at low pH, which is associated with the observed difference in survival.

Continue reading ‘Low pH reduced survival of the oyster Crassostrea gigas exposed to the Ostreid herpesvirus 1 by altering the metabolic response of the host’

Oysters and eelgrass: potential partners in a high pCO2 ocean

Climate change is affecting the health and physiology of marine organisms and altering species interactions. Ocean acidification (OA) threatens calcifying organisms such as the Pacific oyster, Crassostrea gigas. In contrast, seagrasses, such as the eelgrass Zostera marina, can benefit from the increase in available carbon for photosynthesis found at a lower seawater pH. Seagrasses can remove dissolved inorganic carbon from OA environments, creating local daytime pH refugia. Pacific oysters may improve the health of eelgrass by filtering out pathogens such as Labyrinthula zosterae (LZ), which causes eelgrass wasting disease (EWD). We examined how co-culture of eelgrass ramets and juvenile oysters affected the health and growth of eelgrass and the mass of oysters under different pCO(2) exposures. In Phase I, each species was cultured alone or in co-culture at 12 degrees C across ambient, medium, and high pCO(2) conditions, (656, 1,158 and 1,606 mu atm pCO(2), respectively). Under high pCO(2), eelgrass grew faster and had less severe EWD (contracted in the field prior to the experiment). Co-culture with oysters also reduced the severity of EWD. While the presence of eelgrass decreased daytime pCO(2), this reduction was not substantial enough to ameliorate the negative impact of high pCO(2) on oyster mass. In Phase II, eelgrass alone or oysters and eelgrass in co-culture were held at 15 degrees C under ambient and high pCO(2) conditions, (488 and 2,013atm pCO(2), respectively). Half of the replicates were challenged with cultured LZ. Concentrations of defensive compounds in eelgrass (total phenolics and tannins), were altered by LZ exposure and pCO(2) treatments. Greater pathogen loads and increased EWD severity were detected in LZ exposed eelgrass ramets; EWD severity was reduced at high relative to low pCO(2). Oyster presence did not influence pathogen load or EWD severity; high LZ concentrations in experimental treatments may have masked the effect of this treatment. Collectively, these results indicate that, when exposed to natural concentrations of LZ under high pCO(2) conditions, eelgrass can benefit from co-culture with oysters. Further experimentation is necessary to quantify how oysters may benefit from co-culture with eelgrass, examine these interactions in the field and quantify context-dependency.

Continue reading ‘Oysters and eelgrass: potential partners in a high pCO2 ocean’

Seawater acidification reduced the resistance of Crassostrea gigas to Vibrio splendidus challenge: an energy metabolism perspective

Negative physiological impacts induced by exposure to acidified seawater might sensitize marine organisms to future environmental stressors, such as disease outbreak. The goal of this study was to evaluate if ocean acidification (OA) could reduce the resistance capability of the Pacific oyster (Crassostrea gigas) to Vibrio splendidus challenge from an energy metabolism perspective. In this study, the Pacific oyster was exposed to OA (pH 7.6) for 28 days and then challenged by V. splendidus for another 72 h. Antioxidative responses, lipid peroxidation, metabolic (energy sensors, aerobic metabolism, and anaerobic metabolism) gene expression, glycolytic enzyme activity, and the content of energy reserves (glycogen and protein) were investigated to evaluate the environmental risk of pathogen infection under the condition of OA. Our results demonstrated that following the exposure to seawater acidification, oysters exhibited an energy modulation with slight inhibition of aerobic energy metabolism, stimulation of anaerobic metabolism, and increased glycolytic enzyme activity. However, the energy modulation ability and antioxidative regulation of oysters exposed to seawater acidification may be overwhelmed by a subsequent pathogen challenge, resulting in increased oxidative damage, decreased aerobic metabolism, stimulated anaerobic metabolism, and decreased energy reserves. Overall, although anaerobic metabolism was initiated to partially compensate for inhibited aerobic energy metabolism, increased oxidative damage combined with depleted energy reserves suggested that oysters were in an unsustainable bioenergetic state and were thereby incapable of supporting long-term population viability under conditions of seawater acidification and a pathogen challenge from V. splendidus.

Continue reading ‘Seawater acidification reduced the resistance of Crassostrea gigas to Vibrio splendidus challenge: an energy metabolism perspective’

Influence of bacteria on shell dissolution in dead gastropod larvae and adult Limacina helicina pteropods under ocean acidification conditions

Ocean acidification (OA) increases aragonite shell dissolution in calcifying marine organisms. It has been proposed that bacteria associated with molluscan shell surfaces in situ could damage the periostracum and reduce its protective function against shell dissolution. However, the influence of bacteria on shell dissolution under OA conditions is unknown. In this study, dissolution in dead shells from gastropod larvae and adult pteropods (Limacina helicina) was examined following a 5-day incubation under a range of aragonite saturation states (Ωarag; values ranging from 0.5 to 1.8) both with and without antibiotics. Gastropod and pteropod specimens were collected from Puget Sound, Washington (48°33′19″N, 122°59′49″W and 47°41′11″N, 122°25′23″W, respectively), preserved, stored, and then treated in August 2015. Environmental scanning electron microscopy (ESEM) was used to determine the severity and extent of dissolution, which was scored as mild, severe, or summed (mild + severe) dissolution. Shell dissolution increased with decreasing Ωarag. In gastropod larvae, there was a significant interaction between the effects of antibiotics and Ωarag on severe dissolution, indicating that microbes could mediate certain types of dissolution among shells under low Ωarag. In L. helicina, there were no significant interactions between the effects of antibiotics and Ωarag on dissolution. These findings suggest that bacteria may differentially influence the response of some groups of shelled planktonic gastropods to OA conditions. This is the first assessment of the microbial–chemical coupling of dissolution in shells of either gastropod larvae or adult L. helicina under OA.

Continue reading ‘Influence of bacteria on shell dissolution in dead gastropod larvae and adult Limacina helicina pteropods under ocean acidification conditions’

CO2-induced ocean acidification impairs the immune function of the Pacific oyster against Vibrio splendidus challenge: an integrated study from a cellular and proteomic perspective

Highlights

• Combined effects of elevated pCO2 and Vibrio splendidus challenge on the Pacific oyster are investigated.
Vibrio infection aggravates the oyster immunosuppressive effect caused by ocean acidification.
• Vibrio infection aggravates the oyster immunosuppressive effect caused by ocean acidification.
• Ocean acidification may increase the risk of enhanced disease of marine mollusks.

Abstract

Ocean acidification (OA) and pathogenic diseases pose a considerable threat to key species of marine ecosystem. However, few studies have investigated the combined impact of reduced seawater pH and pathogen challenge on the immune responses of marine invertebrates. In this study, Pacific oysters, Crassostrea gigas, were exposed to OA (~2000 ppm) for 28 days and then challenged with Vibrio splendidus for another 72 h. Hemocyte parameters showed that V. splendidus infection exacerbated the impaired oyster immune responses under OA exposure. An iTRAQ-based quantitative proteomic analysis revealed that C. gigas responded differently to OA stress and V. splendidus challenge, alone or in combination. Generally, OA appears to act via a generalized stress response by causing oxidative stress, which could lead to cellular injury and cause disruption to the cytoskeleton, protein turnover, immune responses and energy metabolism. V. splendidus challenge in oysters could suppress the immune system directly and lead to a disturbed cytoskeleton structure, increased protein turnover and energy metabolism suppression, without causing oxidative stress. The combined OA- and V. splendidus-treated oysters ultimately presented a similar, but stronger proteomic response pattern compared with OA treatment alone. Overall, the impaired oyster immune functions caused by OA exposure may have increased the risk of V. splendidus infection. These results have important implications for the impact of OA on disease outbreaks in marine invertebrates, which would have significant economic and ecological repercussions.

Continue reading ‘CO2-induced ocean acidification impairs the immune function of the Pacific oyster against Vibrio splendidus challenge: an integrated study from a cellular and proteomic perspective’

Ocean acidification and pathogen exposure modulate the immune response of the edible mussel Mytilus chilensis

Highlights

  • Exposure to futuristic concentration of pCO2 modulates innate immune response.
  • After OA-stress, gene expression is partially counteracted after pathogen challenge.
  • pCO2 might trigger specific immune-related genes at early stages of infection.
  • Combination of OA and bacterial infection seems to have partial antagonistic effects.


Abstract

Ocean acidification (OA) is one of the main consequences of increasing atmospheric carbon dioxide (CO2), impacting key biological processes of marine organisms such as development, growth and immune response. However, there are scarce studies on the influence of OA on marine invertebrates’ ability to cope with pathogens. This study evaluated the single and combined effects of OA and bacterial infection on the transcription expression of genes related to antioxidant system, antimicrobial peptides and pattern recognition receptors in the edible mussel Mytilus chilensis. Individuals of M. chilensis were exposed during 60 days at two concentrations of pCO2 (550 and 1200 μatm) representing respectively current and future scenario of OA and were then injected with the pathogenic bacterium Vibrio anguillarum. Results evidenced an immunomodulation following the OA exposure with an up-regulation of C-type Lectin and Mytilin B and a down-regulation of Myticin A and PGRP. This immunomodulation pattern is partially counteracted after challenge with V. anguillarum with a down-regulation of the C-type lectin and Mytilin B and the up-regulation of Myticin A. In turn, these results evidence that pCO2-driven OA scenarios might triggers specific immune-related genes at early stages of infection, promoting the transcription of antimicrobial peptides and patterns recognition receptors. This study provides new evidence of how the immune response of bivalves is modulated by higher CO2 conditions in the ocean, as well one factor for the resilience of marine population upon global change scenarios.

Continue reading ‘Ocean acidification and pathogen exposure modulate the immune response of the edible mussel Mytilus chilensis’

Parasitic infection alters the physiological response of a marine gastropod to ocean acidification

Increased hydrogen ion concentration and decreased carbonate ion concentration in seawater are the most physiologically relevant consequences of ocean acidification (OA). Changes to either chemical species may increase the metabolic cost of physiological processes in marine organisms, and reduce the energy available for growth, reproduction and survival. Parasitic infection also increases the energetic demands experienced by marine organisms, and may reduce host tolerance to stressors associated with OA. This study assessed the combined metabolic effects of parasitic infection and OA on an intertidal gastropod, Zeacumantus subcarinatus. Oxygen consumption rates and tissue glucose content were recorded in snails infected with one of three trematode parasites, and an uninfected control group, maintained in acidified (7·6 and 7·4 pH) or unmodified (8·1 pH) seawater. Exposure to acidified seawater significantly altered the oxygen consumption rates and tissue glucose content of infected and uninfected snails, and there were clear differences in the magnitude of these changes between snails infected with different species of trematode. These results indicate that the combined effects of OA and parasitic infection significantly alter the energy requirements of Z. subcarinatus, and that the species of the infecting parasite may play an important role in determining the tolerance of marine gastropods to OA.

Continue reading ‘Parasitic infection alters the physiological response of a marine gastropod to ocean acidification’


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Ocean acidification in the IPCC AR5 WG II

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