bacillota bacillota the bacillota (synonym firmicutes) are a phylum of bacteria, most of which have gram-positive cell wall structure. the renaming of phyla such as firmicutes in 2021 remains controversial among microbiologists, many of whom continue to use the earlier names of long standing in the literature. bacillota bacillus subtilis, gram-stained scientific classification domain: bacteria clade: terrabacteria phylum: bacillotagibbons and murray 2021 classes "desulfotomaculia" watanabe, fukui & kuever 2019 "halanaerobiia" cavalier-smith 2020 "natranaerobiia" sorokin et al. 2021 "tissierellia" alauzet et al. 2014 bacilli ludwig et al. 2010 clostridia rainey 2010 culicoidibacteria neupane et al. 2020 erysipelotrichia ludwig et al. 2010 limnochordia watanabe et al. 2015 negativicutes marchandin et al. 2010 thermolithobacteria sokolova et al. 2007 synonyms "bacillaeota" oren et al. 2015 "bacillota" whitman et al. 2018 "desulfotomaculota" watanabe et al. 2019 "endobacteria" (cavalier-smith 1998) cavalier-smith 2020 "endobacteria" cavalier-smith 1998 "endospora" margulis and schwartz 1998 "firmacutes" gibbons and murray 1978 (approved lists 1980) "firmicutes" corrig. gibbons and murray 1978 (approved lists 1980) "posibacteria" cavalier-smith 2002 the name "firmicutes" was derived from the latin words for "tough skin," referring to the thick cell wall typical of bacteria in this phylum. scientists once classified the firmicutes to include all gram-positive bacteria, but have recently defined them to be of a core group of related forms called the low-g+c group, in contrast to the actinomycetota. they have round cells, called cocci (singular coccus), or rod-like forms (bacillus). a few firmicutes, such as megasphaera, pectinatus, selenomonas and zymophilus, have a porous pseudo-outer membrane that causes them to stain gram-negative. many bacillota (firmicutes) produce endospores, which are resistant to desiccation and can survive extreme conditions. they are found in various environments, and the group includes some notable pathogens. those in one family, the heliobacteria, produce energy through anoxygenic photosynthesis. bacillota play an important role in beer, wine, and cider spoilage. classes the group is typically divided into the clostridia, which are anaerobic, and the bacilli, which are obligate or facultative aerobes. on phylogenetic trees, the first two groups show up as paraphyletic or polyphyletic, as do their main genera, clostridium and bacillus. however, bacillota as a whole is generally believed to be monophyletic, or paraphyletic with the exclusion of mollicutes. phylogeny the currently accepted taxonomy based on the list of prokaryotic names with standing in nomenclature (lpsn) and the national center for biotechnology information (ncbi). 16s rrna based ltp_01_2022 gtdb 07-rs207 by genome taxonomy database archaea bacteria "aquificida" "synergistetes" atribacterota syntrophorhabdia thermotomaculales spirochaetota firmicutes 3 ♦ dictyoglomota "caldicellulosiruptorales" "thermosediminibacteria" "thermoanaerobacteria" "fcb group" firmicutes 2 ♦ "sulfobacillia" "thermaerobacteria" "carboxydothermales" "thermacetogeniales" moorellales "calderihabitantales" "koleobacterales" zhaonellaceae "desulfitibacterales" "syntrophomonadia" gelria ♦ "symbiobacteriia" ♦ actinomycetota deinococcota "melainabacteria" "cyanobacteriota" armatimonadota chloroflexota nitrospirota "thermodesulfobiota" ♦ elusimicrobiota "halanaerobiia" ♦ acidobacteriota chitinivibrionia "planctobacteria "firmicutes" 1 ♦ thermolithobacteria "carboxydocellales" "thermincolia" "desulfofundulaceae" uba4882 "selenomonadia" limnochordia "desulfotomaculota" "desulfotomaculia" "desulfitobacteriia" "peptococcia" "dethiobacteria" "natranaerobiia" "clostridiia" (incl. tissierellia) fusobacteria mycoplasmatota acholeplasmatales erysipelotrichia mollicutes bacilliia "proteobacteria" s.l. ♦ paraphyletic firmicutes firmicutes e "symbiobacteriia" "thermaerobacteria" "sulfobacillia" firmicutes g limnochordia uba4882 bacillota s.s. "bacillia" "selenobacteria" selenomonadia "desulfotomaculota" "carboxydocellales" "carboxydothermales" "thermincolia" "desulfotomaculia" "moorellia" "syntrophomonadia" "dehalobacteriia" "peptococcia" "desulfitobacteriia" firmicutes d "proteinivoracia" "dethiobacteria" "natranaerobiia" "halanaerobiaeota" "halanaerobiia" firmicutes a "thermosediminibacteria" "thermoanaerobacteria" clostridiia s.s. genera more than 274 genera were considered as of 2016 to be within the bacillota phylum, notable genera of bacillota include: bacilli, order bacillales bacillus listeria staphylococcus bacilli, order lactobacillales enterococcus lactobacillus leuconostoc streptococcus clostridia clostridioides clostridium selenomonas erysipelotrichia erysipelothrix clinical significance