Comparative Analysis of Intestinal Microflora Between Two Developmental Stages of Rimicaris kairei, a Hydrothermal Shrimp From the Central Indian Ridge.

Li Qi,Fang-Chao Zhu,Li-Sheng He,Mengke Shi,Chun-Ang Lian

doi:10.3389/fmicb.2021.802888

Abstract

Despite extreme physical and chemical characteristics, deep-sea hydrothermal vents provide a place for fauna survival and reproduction. The symbiotic relationship of chemotrophic microorganisms has been investigated in the gill of Rimicaris exoculata, which are endemic to the hydrothermal vents of the Mid-Atlantic Ridge. However, only a few studies have examined intestinal symbiosis. Here, we studied the intestinal fauna in juvenile and adult Rimicaris kairei, another species in the Rimicaris genus that was originally discovered at the Kairei and Edmond hydrothermal vent fields in the Central Indian Ridge. The results showed that there were significant differences between juvenile and adult gut microbiota in terms of species richness, diversity, and evenness. The values of Chao1, observed species, and ASV rarefaction curves indicated almost four times the number of species in adults compared to juveniles. In juveniles, the most abundant phylum was Deferribacterota, at 80%, while in adults, Campilobacterota was the most abundant, at 49%. Beta diversity showed that the intestinal communities of juveniles and adults were clearly classified into two clusters based on the evaluations of Bray–Curtis and weighted UniFrac distance matrices. Deferribacteraceae and Sulfurovum were the main featured bacteria contributing to the difference. Moreover, functional prediction for all of the intestinal microbiota showed that the pathways related to ansamycin synthesis, branched-chain amino acid biosynthesis, lipid metabolism, and cell motility appeared highly abundant in juveniles. However, for adults, the most abundant pathways were those of sulfur transfer, carbohydrate, and biotin metabolism. Taken together, these results indicated large differences in intestinal microbial composition and potential functions between juvenile and adult vent shrimp (R. kairei), which may be related to their physiological needs at different stages of development.

Highlights

Deep-sea hydrothermal vents are distributed along midocean ridges and are characterized by high temperatures and environments that are sulfide- and iron-rich, with a low pH (White et al, 2006; Möller et al, 2017)
The presence of microorganisms in the gut of R. exoculata from the Mid-Atlantic Ridge (MAR) was first observed by transmission electron microscopy in 2003; subsequent 16S rRNA analysis identified them as mainly Epsilonproteobacteria, Entomoplasmatales, and Deferribacterota (Zbinden and Cambon-Bonavita, 2003)
We identified the species as R. kairei (Supplementary Figure 1), based on the similarity of the c oxidase subunit I (COI) sequence and the phylogenetic tree constructed through MEGA-X (64-bit) (Kumar et al, 2018) and Neighbor-Joining using Tamura 3-parameter model, with 1,000 bootstrap replications

Summary

Introduction

Deep-sea hydrothermal vents are distributed along midocean ridges and are characterized by high temperatures and environments that are sulfide- and iron-rich, with a low pH (White et al, 2006; Möller et al, 2017). In deep-sea hydrothermal vents, symbiosis between macroorganisms and chemoautotrophic microorganisms is a common phenomenon (Goffredi et al, 2004; Goffredi, 2010; Watsuji et al, 2015; Hinzke et al, 2019). The presence of microorganisms in the gut of R. exoculata from the MAR was first observed by transmission electron microscopy in 2003; subsequent 16S rRNA analysis identified them as mainly Epsilonproteobacteria, Entomoplasmatales, and Deferribacterota (Zbinden and Cambon-Bonavita, 2003). Durand et al (2015) further defined the main lineage of resident gut epibionts at five hydrothermal vent locations and analyzed the relationship between the gut microbial communities and the different geographical locations. The microbial proliferation was explored during embryonic development of R. exoculata and increased with aged eggs (Methou et al, 2019)

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Conclusion