Macrococcus
bovicus - carouselicus - caseolyticus - equipercicus

Macromonas
bipunctata

Magnetospirillum
gryphiswaldense - magnetotacticum

Mahella
australiensis

Malikia
granosa - spinosa

Malonomonas
rubra

Mannheimia
haemolytica

Maribacter
dokdonensis - ulvicola

Maricaulis
maris - parjimensis - salignorans - virginensis - washingtonensis

Marichromatium
gracile - purpuratum

Marinibacillus
marinus

Marinilabilia
salmonicolor

Marinilactibacillus
piezotolerans

Marinithermus
hydrothermalis

Marinitoga
camini - hydrogenitolerans - piezophila

Marinobacter
bryozoorum - daepoensis - flavimaris - hydrocarbonoclasticus - koreensis - lipolyticus - sp.

Marinobacterium
georgiense - jannaschii - stanieri

Marinococcus
albus - halophilus - halotolerans

Marinomonas
communis - dokdonensis - polaris - vaga

Marinospirillum
minutulum

Marinovum
algicola

Marmoricola
aurantiacus

Massilia
albidiflava - aurea - dura - lutea - plicata - timonae

Mechercharimyces
asporophorigenens - mesophilus

Megamonas
hypermegale

Megasphaera
cerevisiae - elsdenii - micronuciformis - paucivorans - sueciensis

Meiothermus
cerbereus - chliarophilus - ruber - silvanus - taiwanensis

Melittangium
boletus - lichenicola

Mesonia
algae

Mesophilobacter
marinus

Mesorhizobium
ciceri - huakuii - loti - mediterraneum - tianshanense

Metallosphaera
hakonensis - prunae - sedula

Methanimicrococcus
blatticola

Methanobacterium
aarhusense - alcaliphilum - beijingense - bryantii - congolense - espanolae - formicicum - ivanovii - oryzae - palustre - sp. - subterraneum - thermaggregans - uliginosum

Methanobrevibacter
acididurans - arboriphilicus - curvatus - cuticularis - filiformis - gottschalkii - oralis - ruminantium - smithii - sp. - thaueri - woesei - wolinii

Methanocalculus
chunghsingensis - halotolerans - pumilus - taiwanensis

Methanocaldococcus
fervens - indicus - infernus - jannaschii - vulcanius

Methanococcoides
alaskense - burtonii - methylutens - sp.

Methanococcus
aeolicus - maripaludis - sp. - vannielii - voltae

Methanocorpusculum
aggregans - bavaricum - labreanum - parvum - sinense

Methanoculleus
bourgensis - chikugoensis - marisnigri - palmolei - submarinus - thermophilus

Methanofollis
aquaemaris - formosanus - liminatans - tationis

Methanogenium
boonei - cariaci - frigidum - marinum - organophilum - sp.

Methanohalobium
evestigatum - sp.

Methanohalophilus
euhalobius - halophilus - mahii - portucalensis - sp.

Methanolacinia
paynteri

Methanolobus
bombayensis - oregonensis - taylorii - tindarius - vulcani

Methanomethylovorans
hollandica - thermophila

Methanomicrobium
mobile

Methanomonas
methylovora

Methanoplanus
endosymbiosus - limicola - petrolearius

Methanopyrus
kandleri

Methanosaeta
concilii - harundinacea

Methanosalsum
zhilinae

Methanosarcina
acetivorans - baltica - barkeri - calensis - lacustris - mazei - semesiae - siciliae - sp. - thermophila - vacuolata

Methanosphaera
cuniculi - stadtmanae

Methanospirillum
hungatei

Methanothermobacter
defluvii - marburgensis - thermautotrophicus - thermoflexus - thermophilus - wolfeii

Methanothermococcus
okinawensis - thermolithotrophicus

Methanothermus
fervidus - sociabilis

Methanothrix
thermophila

Methanotorris
formicicus - igneus

Methylobacillus
flagellatus - fructoseoxidans - glycogenes - sp.

Methylobacterium
adhaesivum - aminovorans - aquaticum - extorquens - fujisawaense - hispanicum - isbiliense - lusitanum - mesophilicum - organophilum - podarium - radiotolerans - rhodesianum - rhodinum - sp. - suomiense - thiocyanatum - variabile - zatmanii

Methylocapsa
acidiphila

Methylocella
tundrae

Methylomonas
clara

Methylophaga
alcalica - marina - sulfidovorans - thalassica

Methylophilus
glucoseoxidans - leisingeri

Methylopila
capsulata - helvetica

Methylosarcina
fibrata - quisquiliarum

Methylotenera
mobilis

Methylovorus
glucosotrophus

Microbacterium
aerolatum - arabinogalactanolyticum - arborescens - aurantiacum - aurum - barkeri - chocolatum - dextranolyticum - esteraromaticum - flavescens - foliorum - gubbeenense - halophilum - halotolerans - hominis - hydrocarbonoxydans - imperiale - keratanolyticum - ketosireducens - kitamiense - koreense - lacticum - laevaniformans - liquefaciens - luteolum - maritypicum - natoriense - oleivorans - oxydans - paludicola - paraoxydans - phyllosphaerae - resistens - saperdae - schleiferi - sp. - terrae - terregens - testaceum - thalassium - trichothecenolyticum - ulmi - xylanilyticum

Microbispora
corallina - griseoalba - mesophila - rosea

Microbulbifer
elongatus - hydrolyticus

Micrococcus
luteus - lylae

Microlunatus
phosphovorus

Micromonospora
aurantiaca - auratinigra - carbonacea - chalcea - chersina - citrea - coerulea - coriariae - eburnea - echinaurantiaca - echinofusca - echinospora - endolithica - flavogrisea - fulviviridis - hainanense - halophytica - inositola - inyonensis - matsumotoense - mirobrigensis - nigra - olivasterospora - pallida - peucetia - purpureochromogenes - rosaria - sagamiensis - sp. - viridifaciens

Micropolyspora
sp.

Micropruina
glycogenica

Microscilla
marina - sp.

Microtetraspora
fusca - glauca - malaysiensis - niveoalba - sp.

Microvirgula
aerodenitrificans

Millisia
brevis

Mitsuokella
jalaludinii - multacida

Mobiluncus
curtisii - mulieris

Modestobacter
multiseptatus

Moellerella
wisconsensis

Mogibacterium
timidum

Moorella
glycerini - mulderi - thermoacetica - thermoautotrophica

Moraxella
(Branhamella) - (Moraxella) - boevrei - canis - equi - lacunata - oblonga

Morganella
morganii - psychrotolerans

Moritella
japonica

Muricauda
ruestringensis

Muricoccus
roseus

Myceligenerans
crystallogenes - xiligouense

Mycetocola
lacteus - saprophilus - tolaasinivorans

Mycobacterium
abscessus - aemonae - agri - aichiense - alvei - angelicum - arupense - asiaticum - aurum - austroafricanum - avium - boenickei - bohemicum - botniense - bovis - branderi - brisbanense - brumae - canariasense - celatum - chelonae - chimaera - chitae - chlorophenolicum - chubuense - concordense - confluentis - conspicuum - cookii - cosmeticum - diernhoferi - doricum - duvalii - elephantis - fallax - farcinogenes - flavescens - florentinum - fluoranthenivorans - fortuitum - frederiksbergense - fuerth - gadium - gastri - gilvum - goodii - gordonae - hackensackense - haemophilum - hassiacum - heckeshornense - heidelbergense - hiberniae - hodleri - holsaticum - houstonense - immunogenum - interjectum - intracellulare - kansasii - komossense - kubicae - lacus - lentiflavum - madagascariense - mageritense - malmoense - manitobense - marinum - monacense - montefiorense - moriokaense - mucogenicum - murale - nebraskense - neglectum - neoaurum - neworleansense - nonchromogenicum - novocastrense - obuense - palustre - parafortuitum - parascrofulaceum - paraseoulense - parmense - peregrinum - petroleophilum - phlei - porcinum - poriferae - psychrotolerans - pulveris - pyrenivorans - rhodesiae - saskatchewanense - scrofulaceum - senegalense - seoulense - septicum - shimoidei - simiae - smegmatis - sp. - sphagni - szulgai - terrae - thermoresistibile - tokaiense - triplex - triviale - tusciae - vaccae - vanbaalenii - wolinskyi - xenopi - yunnanensis

Mycoplana
bullata - dimorpha - ramosa

Myroides
odoratus

Myxococcus
flavescens - fulvus - macrosporus - stipitatus - virescens - xanthus