Microbial community and functions associated with digestion of algal polysaccharides in the visceral tract of Haliotis discus hannai: Insights from metagenome and metatranscriptome analysis

PLoS One. 2018 Oct 11;13(10):e0205594. doi: 10.1371/journal.pone.0205594. eCollection 2018.

Abstract

Haliotis discus hannai, a species of Pacific abalone, is a highly valuable food source throughout Northeast Asia. As H. discus hannai primarily feed on brown algae and largely extract their energy from algal polysaccharides, understanding the mechanisms by which they digest algal polysaccharides is essential for elucidating their energy metabolism. Gut microbes, as well as the host animal, are involved in the process of polysaccharide degradation. To identify algal polysaccharide-digestion mechanisms and their origin, we analyzed the metagenome and metatranscriptome of abalone visceral extracts. Microbial communities were characterized using the 16S rRNA gene sequences in the metagenome and our results differed significantly from those of previous studies using traditional microbiological methods such as bacterial cultivation and cloning. A greater diversity of bacterial taxa was identified here than was previously identified using cultivation methods. Furthermore, the most abundant bacterial taxa also differed from previous studies, which is not common when comparing the results of bacterial culturing with those of molecular methodologies. Based on the metatranscriptome, overall functions were identified and additional analyses were performed on the coding sequences of algal polysaccharide-digestive enzymes, including alginate lyase. Results of the transcriptomic analyses suggest that alginate lyase in the visceral extracts of H. discus hannai was produced by the host itself, not by visceral bacteria. This is the first next-generation sequencing study performed on abalone to characterize the visceral microbiota and the source of the ability to digest algal polysaccharides by analyzing the metagenome and metatranscriptome together.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Biodiversity
  • Enzymes / metabolism
  • Gastrointestinal Microbiome / physiology*
  • Metagenome
  • Phaeophyta
  • Phylogeny
  • Polysaccharides / metabolism*
  • RNA, Ribosomal, 16S
  • Snails / metabolism*
  • Snails / microbiology*
  • Transcriptome

Substances

  • Enzymes
  • Polysaccharides
  • RNA, Ribosomal, 16S

Grant support

This research was supported by grants from National Institute of Fisheries Science (Grant Number: R2018021, URL: www.nifs.go.kr (B-HN)) and Rural Development Administration (Grant number: PJ01115901, URL:www.rda.go.kr (SHY)). The two funding source contributed to this study with the same proportions. The C&K genomics provided support in the form of salaries for Jisung Jang, Woori Kwak and Heebal Kim, but did not have any additional role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript. The specific roles of these authors are articulated in the ‘author contributions’ section.