Metabolic diversification of anaerobic methanotrophic archaea in a deep-sea cold seep

Wen-Li Li,Guo-Wei Zhou,Hui Huang,Yu-Zhi Wu,Yong Wang

doi:10.1007/s42995-020-00057-9

Abstract

Anaerobic methanotrophic archaea (ANME) can assimilate methane and govern the greenhouse effect of deep-sea cold seeps. In this study, a total of 13 ANME draft genomes representing five ANME types (ANME-1a, ANME-1b, ANME-2a, ANME-2b and ANME-2c), in size between 0.8 and 1.8 Mbp, were obtained from the Jiaolong cold seep in the South China Sea. The small metagenome-assembled genomes (MAGs) contained all the essential pathways for methane oxidization and carbon dioxide fixation. All genes related to nitrate and sulfate reduction were absent from the MAGs, indicating their syntrophic dependence on partner organisms. Aside from acetate secretion and sugar storage, propanoate synthesis pathway, as an alternative novel carbon flow, was identified in all the MAGs and transcriptionally active. Regarding type-specific features of the MAGs, the genes encoding archaellum and bacteria-derived chemotaxis were specific to ANME-2, perhaps for fitness under fluctuation of methane and sulfate concentration flux. Our genomic and transcriptomic results strongly suggested that ANME could carry out simple carbon metabolism from C1 assimilation to C3 biosynthesis in the SCS cold seep, which casts light on a novel approach for synthetic biology.

Highlights

The cold seeps on the global seafloors are the habitats of chemolithoautotrophic microorganisms that form a unique microbial community structure (Levin 2005)
We reported on the structure of microbial communities and the distribution of functional genes of the core players in four subsurface sediment layers of the Jiaolong cold seep (Wu et al 2018)
Note that the GC contents of ANME-2c metagenome-assembled genomes (MAGs) were all higher than 50%, which indicates that amino acid composition and biological evolution rate of ANME-2c were different from other ANME types (Du et al 2018a)

Summary

Introduction

The cold seeps on the global seafloors are the habitats of chemolithoautotrophic microorganisms that form a unique microbial community structure (Levin 2005). In these ecosystems, the anaerobic oxidation of methane (AOM) coupled with sulfate reduction is an important biogeochemical process in the subsurface sediments with methane leakage (Bowles and Joye 2011). In a cold seep of high methane flow, ANME spread rapidly and must compete for electron acceptors (Boetius and Wenzhofer 2013). Energy metabolism of ANME has been elaborated by previous studies that focused on associations of cross-membrane electron transfer and methane oxidation process (Oni and Friedrich 2017).

Methods

Results

Conclusion