[3] The name "Firmicutes" was derived from the Latin words for "tough skin," referring to the thick cell wall typical of bacteria in this phylum.

[5] The currently accepted taxonomy based on the List of Prokaryotic names with Standing in Nomenclature (LPSN)[6] and the National Center for Biotechnology Information (NCBI).

[citation needed] Archaea "Aquificida" "Synergistetes" Atribacterota Syntrophorhabdia Thermotomaculales Spirochaetota Dictyoglomota "Caldicellulosiruptorales" "Thermosediminibacteria" [incl.

Thermanaeromonas, Desulfovirgula] "FCB group" "Sulfobacillia" "Thermaerobacteria" "Carboxydothermales" "Thermacetogeniales" Moorellales {"Moorellia"} "Calderihabitantales" "Koleobacterales" Zhaonellaceae "Desulfitibacterales" "Syntrophomonadia" Gelria ♦ "Symbiobacteriia" ♦ Actinomycetota Deinococcota "Melainabacteria" "Cyanobacteriota" Armatimonadota Chloroflexota Nitrospirota "Thermodesulfobiota" ♦ Elusimicrobiota "Halanaerobiia" ♦ Acidobacteriota Chitinivibrionia "Planctobacteria Thermolithobacteria "Carboxydocellales" "Thermincolia" "Desulfofundulaceae"

Acetocimmeria" {UBA3575} "Symbiobacteriia" "Sulfobacillia" Limnochordia "Hydrogenisporia" (UBA4882) "Halanaerobiia" "Bacillia" "Proteinivoracia" "Dethiobacteria" "Natranaerobiia" "Selenomonadia" "Syntrophomonadia" "Peptococcia" "Dehalobacteriia" "Desulfitobacteriia" "Thermacetogeniales" {DSM-12270} "Moorellia" "Carboxydocellales" {GCA-003054495} "Thermincolia" "Carboxydothermales" {Z-2901} "Desulfotomaculia" "Thermosediminibacteria" "Thermoanaerobacteria" "Clostridiia" s.s. More than 274 genera were considered as of 2016[update] to be within the Bacillota phylum,[citation needed] notable genera of Bacillota include: Bacilli, order Bacillales Bacilli, order Lactobacillales Clostridia Erysipelotrichia

[15][failed verification] The phylum Bacillota as part of the gut microbiota has been shown to be involved in energy resorption, and potentially related to the development of diabetes and obesity.

[23] The presence of Christensenella (Bacillota, in class Clostridia), isolated from human faeces, has been found to correlate with lower body mass index.