Table 1.

Associations between methanogenic archaea and different diseases or disorders.

Pathology	Association	Method	Citation
IBD - CD	↑ Methanosphaera ↑ Msp-specific IgG	RT-qPCR (MtaB1) Indirect ELISA	Blais Lecours et al. (2014)
	↓ Methanobrevibacter	Metagenomic shotgun sequencing	Lo Sasso et al. (2020)
	↓ Methanobrevibacter	16S rRNA Sequencing	Pascal et al. (2017)
IBD - CD/UC	↓ Methane production	Breath-methane test	Peled et al. (1987)
	↓ Methane production	Breath-methane test	McKay et al. (1985)
	↓ Methanogens	PCR (mcrA)	Scanlan et al. (2008)
	↑ Methanobrevibacter	16S rRNA RT-qPCR	Verma et al. (2010)
	↓ Methanobrevibacter ↑ Methanobrevibacter in remission	16S rRNA RT-qPCR	Ghavami et al. (2018)
	↓ Methane Metabolism	16S rRNA PICRUSt predictions	Nishino et al. (2018)
	↓ Methanobrevibacter	RT-qPCR	Heidarian et al. (2019)
	↓ Methane production	Breath-methane test	Gu et al. (2020)
IBS	No sig. Association	Breath-methane test	Bratten et al. (2008)
	No sig. Association	PCR (mcrA)	Scanlan et al. (2008)
IBS - Constipation	↑ Methane production ↑ Methane with severity	Breath-methane test	Pimentel et al. (2003)
	↑ Methane production ↑ M. smithii	Breath-methane test 16S rRNA RT-qPCR	Ghoshal et al. (2016)
	↑ Transit time	Breath-methane test	Attaluri et al. (2010)
	↑ Transit time	Breath-methane test	Lee et al. (2013)
	↑ Transit time	Breath-methane test	Pimentel et al. (2006)
	↑ Transit time	Breath-methane test	Majewski and McCallum (2007)
	↑ Transit time	Breath-methane test	Hwang et al. (2010)
	↑ Transit time	Breath-methane test	Ghoshal et al. (2011)
	↑ Methane with severity	Breath-methane test	Chatterjee et al. (2007)
	↑ Methanobrevibacter	16S rRNA Sequencing	Pozuelo et al. (2015)
	↑ M. smithii ↑ Methane production	16S rRNA Sequencing Breath-methane test	Kim et al. (2012)
IBS – Diarrhea	↓ Methane production	Breath-methane test	Pimentel et al. (2003)
	↓ Methanobacteriales	16S rRNA RT-qPCR	Tap et al. (2017)
Diverticulosis	↑ Methane production ↑ Methanogen abundance	Breath-methane test Culture-based	Weaver et al. (1986)
Colorectal Cancer	↑ Methane with severity	Breath-methane test	Pique et al. (1984)
	↑ Methane production	Breath-methane test	Haines et al. (1977)
	↓ Methanogen abundance	Breath-methane test	Segal et al. (1988)
	↓ Methanogen abundance	Metagenomic shotgun sequencing	Coker et al. (2020)
	↑ Methanobacteriales ↑ Methanobrevibacter	16S rRNA qPCR	Mira-Pascual et al. (2015)
	No sig. Association	Breath-methane test	O'Keefe et al. (2007)
	No sig. Association	Breath-methane test	Segal et al. (1988)
	No sig. Association	Breath-methane test	Karlin et al. (1982)
	No sig. Association	Breath-methane test	Kashtan et al. (1989)
	No sig. Association	Breath-methane test	Hoff et al. (1986)
	No sig. Association	PCR (mcrA)	Scanlan et al. (2008)
Obesity	↑ Methanogen abundance	16S rRNA Pyrosequencing	Zhang et al. (2009)
	↓ M. smithii	16S rRNA RT-qPCR	Million et al. (2012)
	↓ M. smithii	16S rRNA RT-qPCR	Million et al. (2013)
	↓ M. smithii ↑ Unclassified Methanobrevibacter	Metagenomic shotgun sequencing	Maya-Lucas et al. (2018)
	↑ Methane production	Breath-methane test	Mathur et al. (2013)
	No sig. Association	16S rRNA RT-qPCR	Schwiertz et al. (2010)
	No sig. Association	Breath-methane test 16S rRNA RT-qPCR	Fernandes et al. (2013)
Anorexia	↑ M. smithii	16S rRNA RT-qPCR	Armougom et al. (2009)
	↑ M. smithii	RT-qPCR	Million et al. (2013)
	↑ M. smithii	16S rRNA RT-qPCR	Borgo et al. (2017)
	↑ Methanobrevibacter	16S rRNA Sequencing	Mack et al. (2016)
	↑ M. smithii	16S rRNA Sequencing	Prochazkova et al. (2021)
Malnutrition	↓ M. smithii	Archaeal-specific qPCR	Million et al. (2016)
	↓ M. smithii	16S rRNA RT-qPCR	Camara et al. (2021)
	↑ M. smithii	16S rRNA Sequencing	Kamil et al. (2021)
Encopresis	↑ Methane production	Breath-methane test	Fiedorek et al. (1990)
SBS	↓ M. smithii	16S rRNA RT-qPCR	Boccia et al. (2017)
Mets	↑ Methanobrevibacter	16S rRNA Sequencing	Lim et al. (2017)
Multiple Sclerosis	↑ Methanobrevibacter ↑ Breath methane	16S rRNA Sequencing Breath-methane test	Jangi et al. (2016)
	↑ Methanobrevibacter	16S rRNA Sequencing	Tremlett et al. (2016b)
	↑ Methanobacteriaceae	16S rRNA Sequencing	Jhangi et al. (2014)
Parkinson’s Disease	↑ Methanogen abundance	16S rRNA Sequencing	Qian et al. (2018)
	↑ Methanogen abundance	Metagenomic shotgun sequencing	Bedarf et al. (2017)
SIBO	↑ Breath methane	Breath-methane test	Suri et al. (2018)
	↑ Breath methane	Breath-methane test	Pimentel et al. (2020)
Vaginosis	↑ M. smithii	Antigenic fingerprinting	Belay et al. (1990)
	↑ M. smithii	16S rRNA sequencing	Grine et al. (2019a,b)
Urinary Tract Infection	↑ M. smithii	16S rRNA/McrA PCR RT-qPCR/Culture	Grine et al. (2019a,b)
Anerobic Abscesses	M. smithii*	16S rRNA/McrA Sequencing	Nkamga et al. (2016)
	↑ M. oralis	16S rRNA RT-qPCR/ Metagenomic sequencing	Drancourt et al. (2017)
	M. oralis*	16S rRNA/McrA Sequencing	Nkamga et al. (2018)
Periodontal Disease	↑ M. oralis ↑ M. sp. strain N13	16S rRNA/McrA Sequencing/Culture	Huynh et al. (2015)
	M. massiliense*	Culture	Huynh et al. (2017)
	↑ M. oralis	Archaeal PCR	Li et al. (2009)
Parasitic Infection	↑ Methanobrevibacter	16S rRNA Sequencing	Chen et al. (2021)
Cirrhosis	↓ Methanobrevibacter	16S rRNA Sequencing	Ponziani et al. (2021)

Upward arrows (↑) and downward arrows (↓) represent changes of methanogen abundance and breath-methane excretion, for the respective studies. IBD, Inflammatory bowel disease; CD, Crohn’s Disease; UC, Ulcerative Colitis; IBS, Irritable bowel syndrome; IBS-C, constipation-predominant IBS; IBS-D, diarrhoeal-predominant IBS; SBS, Short Bowel Syndrome; MetS, metabolic syndrome; SIBO, small intestinal bacterial overgrowth. *Denotes detection within respective sample types.