Macrococcus
brunensis - hajekii - lamae

Magnetospirillum
magnetotacticum

Maricaulis
parjimensis - salignorans - sp. - virginensis - washingtonensis

Marinibacillus
marinus

Marinilabilia
salmonicolor

Marinobacter
hydrocarbonoclasticus

Marinobacterium
georgiense - jannaschii - stanieri

Marinococcus
albus - halophilus

Marinomonas
communis - pontica - vaga

Marinospirillum
insulare - minutulum

Martelella
mediterranea

Massilia
timonae

Megamonas
hypermegale

Melissococcus
plutonius

Mesorhizobium
amorphae - chacoense - ciceri - huakuii - loti - mediterraneum - plurifarium - thiogangeticum - tianshanense

Methylobacillus
glycogenes

Methylobacterium
extorquens - mesophilicum - nodulans - organophilum - radiotolerans - rhodesianum - rhodinum - sp. - zatmanii

Methylophaga
thalassica

Methylophilus
methylotrophus

Microbacterium
aerolatum - arabinogalactanolyticum - arborescens - barkeri - esteraromaticum - flavescens - foliorum - gubbeenense - hominis - keratanolyticum - kitamiense - lacticum - laevaniformans - liquefaciens - luteolum - maritypicum - paraoxydans - phyllosphaerae - resistens - saperdae - schleiferi - terrae - terregens - testaceum - thalassium - trichothecenolyticum - ulmi

Microbulbifer
elongatus

Microcella
putealis

Micrococcus
luteus - lylae

Micromonospora
mirobrigensis

Microscilla
arenaria - furvescens - marina - sericea

Microvirgula
aerodenitrificans

Mobiluncus
curtisii - mulieris

Moellerella
wisconsensis

Moraxella
(Branhamella) - (Moraxella) - canis - lincolnii - saccharolytica - sp. - suis

Morganella
morganii

Moritella
abyssi - profunda

Muricauda
ruestringensis

Mycetocola
lacteus - saprophilus - tolaasinivorans

Mycobacterium
aichiense - alvei - aurum - hodleri - komossense - neoaurum - peregrinum - phlei - psychrotolerans - smegmatis - terrae

Mycococcus
luteus

Mycoplana
bullata - dimorpha - ramosa

Myroides
odoratimimus - odoratus