Abstract
In a previous study, we found that the growth performance of the new strain of Huanghe carp is related to gene expression and bacterial community in the gut. In order to better understand the relationship between the gene expression level and bacterial abundance in the gut, we studied the growth performance, gut bacterial structure, and transcriptome profile in the 4th generation of the new carp strain (selection group) at harvesting time, and compared them with the control line (traditional Huanghe carp). Body weight, depth, width, and length increased 14.58, 7.14, 5.04, and 5.07%, respectively. The gut microbiome of the selection group also exhibited significantly higher species diversity parameters (Shannon, Simpson, and chao1). Both PCA and phylogenetic analyses divided all gut samples into two parts: control and selection group. Aeromonas was the dominant taxon in the control group, followed by Firmicutes and Roseomonas; in the selection group, Roseomonas was the dominant taxon, followed by Firmicutes and then Aeromonas. Among the 249 significantly differentially expressed genes, 194 were downregulated and 55 were upregulated. Functional GO annotation produced 13 terms in the biological process, 8 in the cellular component, and 7 in the molecular function categories. KEGG annotation indicated that most of these genes were associated with the immune-related pathways. A total of 2,892 pairs of genes (245) and baceterial genera (256) were analyzed using Pearson’s correlation analysis. Most of the identified associations were mapped to the immune system, bacterial community, and cell differentiation categories. The top-10 bacterial genera identified by these analyses were Methylocystis, Ohtaekwangia, Roseomonas, Shewanella, Lutispora, GpVI, Desulfovibrio, Candidatus_Berkiella, Bordetella, and Azorhizobium. Genes paired with bacteria flora were divided into four functional categories: immune, growth, adipocyte differentiation, and nerve regulation. These genes may be related to the comparatively fast growth and high muscle polyunsaturated fatty acid content of the Huanghe carp new strain. Meanwhile, nerve regulation-related genes may be a reflection of the microbiota-gut-brain axis. These results illustrate that gut bacterial community structure is associated with the growth performance and gene expression in the Huanghe carp new strain.
Highlights
In recent years, the influence of gut microbes on the host’s production performance has received extensive attention
A comparative study of the structure of the intestinal microbial flora of transgenic carp [Based on the technique of microinjection, recombinant recombinant grass carp (Ctenopharyngodon idellus) growth hormore gene has been transferred into fish eggs] and wild carp found that Proteobacteria, Fusobacteria, Bacteroides, and Firmicutes exhibited significant differences in abundance, and that carbohydrate significantly increased in the transgenic carp
In a study of the structure of intestinal microflora during different growth stages of Litopenaeus vannamei culture, it was found that Proteobacteria, Bacteroides, and Actinomycetes were observed in all growth stages, but dominant species varied among the growth stages: Comamonadaceae of Betaproteobacteria at 2 weeks and 1 month, Flavobacteria at 2 months, and Vibrio at 3 months (Huang et al, 2016)
Summary
The influence of gut microbes on the host’s production performance has received extensive attention. The influence of microorganisms on host gene expression is highly site-specific, and each cell fraction is enriched with specific transcriptional regulators (Sommer et al, 2015) This influence is mainly achieved through the gut-brain axis and the gut-hepatic axis. The mechanism may involve the stimulation of rumen ketogenesis and butyrate metabolism by genes hydroxymethylglutaryl-CoA lyase, mitochondrial (HMGCL), and 3-hydroxy-3-methylglutaryl-CoA synthase 2 mitochondrial (HMGCS2), as well as by the change of fermentation type caused by rumen microbiota (Wang et al, 2016). In this microbe-gene expression pattern of the gut-hepatic axis, another important research direction is the change of circadian rhythm. When the rhythm of the homeostasis of the microbial community is disrupted, the normal chromatin and gene expression levels of the host will vary, and the new mechanism of gene expression in the genome’s gut-hepatic axis will be activated (Thaiss et al, 2016)
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