Biology subjects

Gourbal, B.

Publications and source records attributed to Gourbal, B..

5 recordsLinked to original sources

bioRxiv2024

Evidences that host genetic background more than the environment shapes the microbiota of the snail Bulinus truncatus, an intermediate host of Schistosoma species.

Microbiota are increasingly recognized as key players in regulating host biological functions, influencing both the ecology and evolution of organisms. However, the factors shaping microbiota diversity and structure in natural environments remain underexplored, especially the relative importance of host genetics versus environmental factors. In this study, we address this gap using the freshwater snail Bulinus truncatus, an intermediate host for some human and animal Schistosoma parasites, as a model species. We developed 31 new microsatellite markers to assess the population structure of B. truncatus across 9 sites in Senegal. We then applied metabarcoding to characterize the diversity and structure of individual snail bacterial microbiota and environmental communities associated with each sampling site using environmental DNA. We also used molecular diagnostics to determine trematode infection status of B. truncatus individuals. By integrating these data through multiple regression on distance matrices (MRM) analyses, we quantified the influence of B. truncatus population genetics, spatial distribution, environmental bacterial communities, and infection status on the snails microbiota structure. Our results show that the genetic structure of B. truncatus populations, and to a lower extent geographic distribution, are the main factors explaining the snails microbiota compositions. Neither the environmental bacterial communities nor trematode infection status significantly contributed to microbiota structure. A portion of the variance in microbiota composition remains unexplained, suggesting that additional ecological or intrinsic factors might be involved. These findings provide new insights into the drivers of microbiota structure in natural populations and highlight the complexity of host-microbiota-environment interactions. Key-words: Bulinus truncatus, Microbiota, Spatial structure, Population genetics, Trematodes, Multiple regressions on distance matrices

ecology↗

bioRxiv2024

Diversity and functional specialization of oyster immune cells uncovered by integrative single cell level investigations

Mollusks are a major component of animal biodiversity and play a critical role in ecosystems and global food security. The Pacific oyster, Crassostrea (Magallana) gigas, is the most farmed bivalve mollusk in the world and is becoming a model species for invertebrate biology. Despite the extensive research on hemocytes, the immune cells of bivalves, their characterization remains elusive. Here we were able to extensively characterize the diverse hemocytes and identified at least seven functionally distinct cell types and three hematopoietic lineages. A combination of single-cell RNA sequencing, quantitative cytology, cell sorting, functional assays and pseudo-time analyses was used to deliver a comprehensive view of the distinct hemocyte types. This integrative analysis enabled us to reconcile molecular and cellular data and identify distinct cell types performing specialized immune functions, such as phagocytosis, reactive oxygen species production, copper accumulation, and expression of antimicrobial peptides. This study emphasized the need for more in depth studies of cellular immunity in mollusks and non-model invertebrates and set the ground for further comparative immunology studies at the cellular level.

immunology↗

bioRxiv2018

Dysbiosis of the Biomphalaria glabrata vector snail microbiota following infection by Schistosoma parasites

Host-associated microbiota cari affect the fitness of its host i {eta} a number of ways, including the modification of host-parasite interactions and thus the outcome of disease. Biomphalaria glabrata is the vector snail of the trematode Schistosoma mansoni, the agent of human schistosomiasis, causing hundreds of thousands of deaths every year. Here, we present the first study of the snail bacterial microbiota in response to Schistosoma infection. To examine the interplay between B. glabrata, S. mansoni and snail microbiota, snails were infected and the microbiota composition was analysed by massive 16S rDNA amplicon sequencing approach. We characterized the Biomphalaria bacterial microbiota at the individual level in both naive and infected snails. Sympatric and allopatric strains of parasites were used for infections and re{-}infections to analyse the modification or dysbiosis of snail microbiota in different host-parasite co-evolutionary contexts. Concomitantly, using RNAseq data, we investigated the link between bacterial microbiota dysbiosis and snail anti-microbial peptide immune response. This work paves the way for a better understanding of snail/schistosome interaction, and would have critical consequences in terms of snail control strategies for fighting schistosomiasis disease in the field.

microbiology↗

bioRxiv2018

Sympatric and allopatric evolutionary contexts shape differential immune response in Biomphalaria / Schistosoma interaction

Selective pressures between hosts and their parasites can result in reciprocal evolution or adaptation of specific life history traits. Local adaptation of resident hosts and parasites should lead to host-parasite systems performing better in sympatry when compared to allopatry. Between-population variations in parasite infectivity/virulence and host defence/resistance, referred to as compatibility phenotype, were often the proxy used to analyse sympatric or allopatric adaptation. Nevertheless, some reported cases exist where allopatric host-parasite systems demonstrate compatibility phenotypes similar or greater than the one observed in sympatry. In these cases, the role of local adaptation is worth considering. Here, we study the interaction between Schistosoma and its vector snail Biomphalaria in which such a discrepancy in local versus foreign compatibility phenotype has been observed. Herein, we developed an integrative approach to investigate sympatric and allopatric interaction processes and link the underlying molecular mechanisms to the resulting phenotypes. Using comparative \"omics\" approaches joined to analysis of life history traits (immune cellular response, mortality, prevalence and compatibility) we tried to bridge the gap of knowledge that exists for connecting local adaptation observations to molecular phenotypes in Schistosoma/Biomphalaria interactions.\n\nWe found that despite displaying similar prevalence phenotypes, parasite infection triggered an immune suppression in snails living in sympatry, while it activated an immune response for those living in allopatry. Dual-comparative molecular analyses revealed that parasite infection causes immune suppression in sympatry. miRNAs were used to hijack the hosts immune response, allowing sympatric parasites to initiate their developmental program earlier and more efficiently.\n\nWe show that despite having similar prevalence phenotypes, sympatric and allopatric snail-Schistosoma interactions displayed a strongly different immunobiological molecular dialogue. The ability of allopatric pathogens to adapt rapidly and efficiently to new hosts could have critical consequences on disease emergence and risk of schistosomiasis outbreaks. These observations would have important consequences in term of schistosomiasis disease control.

immunology↗

bioRxiv2018

BgTEP: an antiprotease involved in innate immune sensing in Biomphalaria glabrata

Insect Thioester-containing protein (iTEP) is the most recently defined group among the TEP superfamily. TEPs are key components of the immune system, and iTEPs from flies and mosquitoes were shown to be major immune weapons. Initially characterised from insects, TEP genes homologous to iTEP were further described from several other invertebrates including arthropods, cniderians and mollusks albeit with few functional characterisations. In the freshwater snail Biomphalaria glabrata, a vector of the schistosomiasis disease, the presence of a TEP protein (BgTEP) was previously described in a well-defined immune complex involving snail lectins (FREP) and schistosome parasite mucins (SmPoMuc).\n\nTo investigate the potential role of BgTEP in the immune response of the snail, we first characterised its genomic organisation and its predicted protein structure. A phylogenetic analysis clustered BgTEP in a well-conserved subgroup of mollusk TEP. We then investigated the BgTEP expression profile in different snail tissues, and followed immune challenges using different kinds of intruders during infection kinetics. Results revealed that BgTEP is particularly expressed in hemocytes, the immune-specialised cells in invertebrates, and is secreted into the hemolymph. Transcriptomic results further evidenced an intruder-dependent differential expression pattern of BgTEP whilst interactome experiments showed that BgTEP is capable of binding to the surface of different microbes and parasite either in its full length form or in processed forms.\n\nThrough this work, we report the first characterisation of a snail TEP. Our study also reveals that BgTEP may display an unexpected functional dual-role. In addition to its previously characterised anti-protease activity, we demonstrate that BgTEP can bind to the intruder surface membrane, which supports a likely opsonin role.

immunology↗