Abstract
Remarkably little information is available about the interaction between the gut microbiota and intestinal immunity in fish and crustaceans. In our study, we used Illumina MiSeq sequencing and real-time quantitative PCR to compare the microbial community and immunity genes expression in the foregut, midgut and hindgut of Chinese mitten crab (Eriocheir sinensis). Our results indicated that the community richness of the midgut is higher than in the foregut or the hindgut, although the bacterial diversity in the hindgut is higher. The predominant phyla were Tenericutes and Firmicutes in the foregut, Tenericutes and Proteobacteria in the midgut and Proteobacteria, Tenericutes and Bacteroidetes in the hindgut. When compared with the midgut, the expression of antimicrobial peptides (AMPs) were significantly elevated in the hindgut (P < 0.05), and the gene expression of EsRelish (IMD pathway) was higher than the Toll signaling pathway genes. Actinobacteria and Lactobacillus had negative correlationship with the expression of AMPs, although Acinetobacter, Bacteroides, Flavobacterium can up-regulate the expression of AMP genes. Collectively, our data indicate that microbiota are site-specific within the digestive tracts of crabs and the bacterial community and intestinal immunity have a close relationship in E. sinensis.
Highlights
The connections between gut flora and host was one of the most important impactors influence aquatic animal health (Chaiyapechara et al 2012; Yan et al 2012)
Our results suggest a role for the dominant bacteria in each region of the digestive tract and provide novel insight into the bacterial community and gut immunity of E. sinensis
Bacterial composition determined by MiSeq sequencing Microbial community of the digestive tract was determined using Illumina MiSeq. 32128 sequences were obtained by quality screening for alpha-diversity research
Summary
The connections between gut flora and host was one of the most important impactors influence aquatic animal health (Chaiyapechara et al 2012; Yan et al 2012). The intestinal flora is vital to the development (Shang et al 2017), immunity and disease resistance of gut (CerfBensussan and Gaboriau-Routhiau 2010). Antimicrobial peptides (AMPs) play a crucial role in gut immunity (Destoumieux-Garzón et al 2016; Zhang and Gallo 2016) and form effective defense mechanisms against multitudinous pathogens. Many studies on AMPs and invertebrate gut defense have been performed in insects, especially Drosophila melanogaster, because this species is the model organism of invertebrate (Broderick 2016; Loch et al 2017; Rolff and SchmidHempel 2016). The key role of AMPs in gut immune response is demonstrated through oral reactive oxygen species (ROS) blockers to Drosophila mutants
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