# Structure and diversity of intestinal methanogens in black carp (Mylopharyngodon piceus), grass carp (Ctenopharyngodon idella) and water samples

## TL;DR

This study explores the types and amounts of methane-producing microbes in the intestines of black and grass carp and their pond water, finding similar patterns between fish and water samples.

## Contribution

The study identifies dominant methanogen genera in fish intestines and water, revealing their correlation and metabolic pathways.

## Key findings

- Methanosarcina and Methanocorpusculum were the dominant methanogen genera in fish intestines and pond water.
- Grass carp had the highest abundance of Methanosarcina, while black carp had the most Methanocorpusculum.
- Hydrotrophic metabolism was the main pathway for these methanogens.

## Abstract

The present research investigation aims to examine the community features of methanogens in the intestinal tract of black and grass carp, as well as their association with methanogens in water samples. Samples of black carp, grass carp and water in a pond were gathered in Spring 2021. Using the Illumina HiSeq 2500 high-throughput sequencing platform, the metagenomic mcrA gene sequences of black carp, grass carp and cultured water specimens were determined and analyzed. The outcomes indicate that the richness and diversity of methanogens in the intestinal tract of black and carp grass carp were highly correlated with the cultured water. Five bacterial genera were found in the three sets of samples, Methanosarcina, Methanocorpusculum, Methanospirillum, Methanobacterium and Methanofollis, in which Methanosarcina and Methanocorpusculum were the dominant genera. In addition, Methanosarcina had the greatest amount in grass carp and Methanocorpusculum had the greatest quantity in black carp. In conclusion, Methanosarcina and Methanocorpusculum were the main methanogens in the digestive tract of black and grass carp and culture water, and hydrolytic fermentative bacteria were its main metabolic substrate, hydrotrophic was its main metabolic pathway. The results will provide a reference for the relationship between intestinal methanogens and aquaculture and the greenhouse effect.