Abstract
Me.tha.no.tri.cha'les. N.L. fem. n.
Methanothrix
type genus of the order; suff. ‐
ales
the ending to denote an order; N.L. fem. pl. n.
Methanotrichales
the order of
Methanothrix
.
Cells are nonmotile, sheathed rods with flat ends. Gram‐stain negative. Lipids contain
myo
‐inositol, ethanolamine, and galactose as the polar head groups. Species are oxygen‐tolerant anaerobe. However, growth and methanogenesis can only occur in strictly anaerobic and highly reducing conditions. Energy is obtained by splitting acetate into methane and CO
2
. When cocultured with electrogenic
Geobacter
spp., CO
2
is reduced to methane via direct interspecies electron transfer (DIET). Optimum growth pH range is 7.0–7.8. Mesophilic and thermophilic. Optimum growth temperatures are 34–37°C for mesophilic strains and 55–60°C for thermophilic strains. They occupy a wide range of anoxic habitats including anaerobic river mud, paddy field soil, hot springs, thermal lakes, thermophilic, and mesophilic anaerobic wastewater digesters treating domestic wastes; granular sludge, anaerobic fixed‐bed reactors, and other types of anaerobic systems. Genome sequences have been determined for strains of all three of the described species in the order, and the genome size ranges from 1.9 to 3.0 Mb. The order
Methanotrichales
consists of one family
Methanotrichaceae
. Although all three described species are currently classified in a single genus
Methanothrix
, phylogenomic analyses suggest that two species should be transferred to novel genera.
DNA G + C content (mol%)
: 51–61 (Genome).
Type genus
:
Methanothrix
Huser et al. 1982, VL10.
Taxonomic and Nomenclature Notes
According to the List of Prokaryotic names with Standing in Nomenclature (LPSN), the taxonomic status of the order
Methanotrichales
is: synonym (and no standing) (last update, February 2025)
*
. Correct name:
Methanosarcinales
LPSN classification:
Archaea
/
Methanobacteriati
/
Methanobacteriota
/
Methanosarcinia
/
Methanosarcinales
The order
Methanotrichales
can also be recovered in the Genome Taxonomy Database (GTDB) as
o__Methanotrichales
(version v220)
**
.
GTDB classification:
d__Archaea
/
p__Halobacteriota
/
c__Methanosarcinia
/
o__Methanotrichales
*
Meier‐Kolthoff
et al. (
2022
).
Nucleic Acids Res
,
50
,
D801
–
D807
; DOI:
10.1093/nar/gkab902
**
Parks
et al. (
2022
).
Nucleic Acids Res
,
50
,
D785
–
D794
; DOI:
10.1093/nar/gkab776