Multiple Changes in Peptide and Lipid Expression Associated with Regeneration in the Nervous System of the Medicinal Leech

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Polychaetes as annelid models to study ecoimmunology of marine organisms

International audienc

Screening for antibacterial molecules in meiobenthic nematodes belonging to the Oncholaimidae family

Active substances such as antimicrobial peptides (AMPs) defined as antibiotics naturally produced by all living species, have already been characterized and identified from various marine organisms (fish, sponges, annelids, echinoderms, crustaceans, molluscs and tunicates) except from nematodes. In this study, we investigated the biochemical isolation of antibacterial substances from three free-living marine nematodes belonging to the Oncholaimidae family that dominated meiofauna of two coastal environments characterized by reduced and hypoxic sediments with high concentration of sulfides (Roscoff Harbour in France and Secca delle Fumose in Italy). There are no consensus sequences for AMPs which are even more diversified in the marine environment compared to the terrestrial one. A bioassay guided purification protocol was used since it constitutes the only method to find novel active peptides. Data showed the potential of two of the three nematodes species as interesting sources of small sized antibiotics. The third species showed an occasional epi-symbiotic association with filamentous bacteria, but singularly lacked antimicrobial activity. The lack of biological material did not allow the identification of the antimicrobial molecules

Screening for antibacterial molecules in meiobenthic nematodes belonging to the Oncholaimidae family

Active substances such as antimicrobial peptides (AMPs) defined as antibiotics naturally produced by all living species, have already been characterized and identified from various marine organisms (fish, sponges, annelids, echinoderms, crustaceans, molluscs and tunicates) except from nematodes. In this study, we investigated the biochemical isolation of antibacterial substances from three free-living marine nematodes belonging to the Oncholaimidae family that dominated meiofauna of two coastal environments characterized by reduced and hypoxic sediments with high concentration of sulfides (Roscoff Harbour in France and Secca delle Fumose in Italy). There are no consensus sequences for AMPs which are even more diversified in the marine environment compared to the terrestrial one. A bioassay guided purification protocol was used since it constitutes the only method to find novel active peptides. Data showed the potential of two of the three nematodes species as interesting sources of small sized antibiotics. The third species showed an occasional epi-symbiotic association with filamentous bacteria, but singularly lacked antimicrobial activity. The lack of biological material did not allow the identification of the antimicrobial molecules

A single coelomic cell type is involved in both immune and respiratory functions of the coastal bioindicator annelid: Capitella C-Channel1 from the English Channel

International audienceThe polychaete Capitella is a typical member of the ‘thiobiome’, and is commonly used as an eutrophication indicator species in environmental assessment studies. To deal with a sulfide-rich and poisonous surrounding, cells in close contact with the environment, and thus able to play a major role in detoxication and survival, are circulating cells. This work aimed to morpho-functionally describe the circulating coelomic cells of Capitella from the English Channel inhabiting the sulfide-rich mud in Roscoff Harbor. In general, worms have three types of circulating cells, granulocytes involved in bacterial clearance and defense against microorganisms, eleocytes with an essentially trophic role and elimination of cellular waste, and erythrocytes which play a role in detoxification and respiration via their intracellular hemoglobin. By combining diverse microscopic and cellular approaches, we provide evidence that Capitella does not possess granulocytes and eleocytes, but rather a single abundant rounded cell type with the morphological characteristics of erythrocytes i.e. small size and production of intracellular hemoglobin. Surprisingly, our data show that in addition to their respiratory function, these red cells could exert phagocytic activities, and produce an antimicrobial peptide. This latter immune role is usually supported by granulocytes. Our data highlight that the erythrocytes of Capitella from the English Channel differ in morphology and bear more functions than the erythrocytes of other annelids. The simplicity of this multi-task (or polyvalent) single-cell type makes Capitella an interesting model for studies of the impact of the environment on the immunity of this bioindicator species

Transgenerational Immune Priming in the Field: Maternal Environmental Experience Leads to Differential Immune Transfer to Oocytes in the Marine Annelid Hediste diversicolor

Transgenerational immune priming (TGIP) is an intriguing form of parental care which leads to the plastic adjustment of the progeny’s immunity according to parental immune experience. Such parental effect has been described in several vertebrate and invertebrate taxa. However, very few empirical studies have been conducted from the field, with natural host-parasite systems and real ecological settings, especially in invertebrates. We investigated TGIP in wild populations of the marine annelid Hediste diversicolor. Females laid eggs in a mud tube and thus shared the local microbial threats with the first developmental stages, thus meeting expectations for the evolution of TGIP. We evidenced that a maternal bacterial challenge led to the higher antibacterial defense of the produced oocytes, with higher efficiency in the case of Gram-positive bacterial challenge, pointing out a prevalent role of these bacteria in the evolutionary history of TGIP in this species. Underlying mechanisms might involve the antimicrobial peptide hedistin that was detected in the cytoplasm of oocytes and whose mRNAs were selectively stored in higher quantity in mature oocytes, after a maternal immune challenge. Finally, maternal immune transfer was significantly inhibited in females living in polluted areas, suggesting associated costs and the possible trade-off with female’s protection

Day/night variations of feeding and immune activities in larvae of the European grapevine moth, Lobesia botrana.

14 pagesInternational audienceDaily varying intensities of exposure to infectious enemies should select for the evolution of a daily structure of host immunity with a marked peak and trough (i.e. a daily rhythm). Such nychthemeral variations have been documented for insect inducible immunity (responsiveness to microbial challenge), while the existence of similar daily patterns in basal immunity remains unexplored. Basal immunity is defined as the background, readily available protection aimed at preventing infection at any time. Daily rhythmic elevation of basal immunity should bear substantial costs and be performed only when facing highly predictable changes in threat of infection. This could be the case for risk of food-borne infection, presumably fluctuating with daily patterns of host feeding activity. This study investigated the existence of day/night variations in feeding activity and basal immunity, using larvae of the moth Lobesia botrana (Lepidoptera: Tortricidae) raised under a realistic daily cycle of light and temperature conditions. At night, larvae (i) spent a greater amount of time feeding, (ii) displayed a higher total phenoloxidase activity and (iii) underwent subtle changes in the balance of some haemocyte types newly described for this species (increase in the relative abundances of prohaemocytes and plasmatocytes, decrease in the one of oenocytoids). These data provide the first evidence of nychthemeral variations of basal immunity in an insect model, with peaks in some immune effectors co-occurring with maximal feeding activity (during nighttime). The ecological implications and the contribution of this work to improve the general understanding of the temporal structure of immunity are discussed

Hedistin: A novel antimicrobial peptide containing bromotryptophan constitutively expressed in the NK cells-like of the marine annelid, Nereis diversicolor

A novel antimicrobial peptide, named hedistin was identified from the coelomocytes of Nereis diversicolor. Hedistin shows no obvious similarities with other known peptides and constitutes the first antimicrobial peptide containing bromotryptophans demonstrated in annelids. cDNA and mass spectrometry analysis revealed that, upon bacteria challenge, this peptide is secreted following processing of a precursor containing a signal peptide and prosequences. Hedistin was shown to possess an activity against a large spectrum of bacteria including the methicillin resistant Staphylococcus aureus and Vibrio alginolyticus. The gene was demonstrated to be constitutively and exclusively expressed in circulating NK cells like known to play an important role in the immunity of the sand worm. These data contrast with those observed in another annelid, the leech, in which genes coding for antimicrobial peptides are upregulated in a specific tissue and peptides are rapidly released into the hemolymph after septic injury