# Cultivation and genomic characterization of novel methanogens from arid desert biocrust

## TL;DR

Scientists discovered new methane-producing microbes in dry desert soils, challenging previous ideas about where these microbes can live.

## Contribution

The study reports the genomic characterization of seven novel methanogenic cultures from arid environments, revealing their genetic adaptations and ecological plasticity.

## Key findings

- Six of the seven methanogenic cultures represent new species, but are phylogenetically close to anoxic environment organisms.
- Methanobacterium spp. have fewer genes for oxygen and desiccation tolerance compared to other methanogens.
- Global metagenomic analysis suggests methanogens are underdetected in dryland soils due to sequencing limitations.

## Abstract

Methanogens are strictly anaerobic archaea capable of energy conservation by methane production, yet their presence in oxic and arid environments challenges existing paradigms. In this study, we enriched and genomically characterized seven methanogenic cultures from desert biocrusts, affiliated with the genera Methanobacterium, Methanosarcina, and Methanocella. Six of these new enrichment cultures represent new species. Nonetheless, phylogenomic analyses revealed close genetic relationships with organisms from anoxic environments, indicating the absence of an evolutionary distinction. Comparative genomics exposed diverse though non-unique repertories of antioxidant (e.g. catalase, superoxide dismutase and desulfoferrodoxin), and desiccation-resistance genes (including genes for maintaining osmotic pressure and repair of cell wall and membrane), with Methanobacterium spp possessing the lowest gene abundance and diversity for oxygen and desiccation tolerance. Nevertheless, the occurrence of a Class I methanogen such as Methanobacterium in arid soils challenges the notion that members of this class are less oxygen tolerant than Class II. Pangenome analysis further uncovered unique genes enriched in membrane-associated functions and potentially non-functional stress-related genes. Via a global metagenomic survey we find that methanogens are underdetected in dryland soils, likely due to sequencing depth limitations. Our findings highlight previously overlooked methanogen diversity and ecological plasticity in oxic and desiccated habitats, and emphasize the need for further studies to elucidate their survival strategies.