Bacillota

Bacillota
Bacillus subtilis, Gram-stained
Scientific classification
Domain:	Bacteria
(unranked):	Terrabacteria
Phylum:	Bacillota Gibbons and Murray 2021[1]
Classes
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 "Tissierellia" Alauzet et al. 2014 Unassigned Families "Beduinellaceae" Traore et al. 2016 Unassigned Genera "Acidibacillus" Holanda et al. 2015 "Alterileibacterium" Boxberger et al. 2019 Caecibacterium Oren et al. 2019 "Caldinitratiruptor" Fardeau et al. 2010 Capillibacterium Ungkulpasvich et al. 2021 "Candidatus Carbonibacillus" corrig. Kadnikov et al. 2018 "Colidextribacter" Ricaboni et al. 2017 "Desulfobacillus" Johnson et al. 2009 "Candidatus Desulfopertinax Jungbluth et al. 2017 "Candidatus Desulforudis" Chivian et al. 2008 "Desulfosporomusa" Sass et al. 2004 "Candidatus Ferrisolea Pfleiderer et al. 2013 "Candidatus Heliomonas" Asao et al. 2012 "Massilistercora" Tall et al. 2020 "Ndongobacter" Brahimi et al. 2017 Negativibacillus Valles et al. 2021 "Candidatus Soleaferrea" Pfleiderer et al. 2013 "Candidatus Stoquefichus Pfleiderer et al. 2013 "Trigonala" Zhang et al. 2016
Synonyms
"Bacillaeota" Oren et al. 2015 "Bacillota" Whitman et al. 2018 "Desulfotomaculota" Watanabe et al. 2019 "Endospora" Margulis and Schwartz 1998 "Endobacteria" Cavalier-Smith 1998 "Endobacteria" (Cavalier-Smith 1998) Cavalier-Smith 2020 "Firmacutes" Gibbons and Murray 1978 (Approved Lists 1980) "Firmicutes" corrig. Gibbons and Murray 1978 (Approved Lists 1980) "Posibacteria" Cavalier-Smith 2002

The Bacillota (synonym Firmicutes) are a phylum of bacteria, most of which have gram-positive cell wall structure.^[2] A few, however, such as Megasphaera, Pectinatus, Selenomonas and Zymophilus, have a porous pseudo-outer membrane that causes them to stain gram-negative. Scientists once classified the Bacillota 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).

Many Bacillota 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.^[3] However, Bacillota as a whole is generally believed to be monophyletic, or paraphyletic with the exclusion of Mollicutes.^[4]

Phylogeny

A phylogeny by Annotree^[5] and GTDB release 05-RS95 (17 July 2020).^[6]

This second phylogeny is based on 16S rRNA-based LTP release 132 by the All-Species Living Tree Project,^[7] with the currently accepted taxonomy based on the List of Prokaryotic names with Standing in Nomenclature (LPSN),^[8] National Center for Biotechnology Information (NCBI),^[9] and some non-validated clade names from Genome Taxonomy Database.^[10]

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

Bacillota make up ~30% of the mouse and human gut microbiome.^[11] 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.^{[12][13][14][15]} Within the gut of healthy human adults, the most abundant bacterium: Faecalibacterium prausnitzii (F. prausnitzii), which makes up 5% of the total gut microbiome, is a member of the Bacillota phylum. This species is directly associated with reduced low-grade inflammation in obesity.^[16] F. prausnitzii has been found in higher levels within the guts of obese children than in non-obese children.

In multiple studies a higher abundance of Bacillota has been found in obese individuals than in lean controls. A higher level of Lactobacillus (of the Bacillota phylum) has been found in obese patients and in one study, obese patients put on weight loss diets showed a reduced amount of Bacillota within their guts.^[17]

Diet changes in mice have also been shown to promote changes in Bacillota abundance. A higher relative abundance of Bacillota was seen in mice fed a western diet (high fat/high sugar) than in mice fed a standard low fat/ high polysaccharide diet. The higher amount of Bacillota was also linked to more adiposity and body weight within mice.^[18] Specifically, within obese mice, the class Mollicutes (within the Bacillota phylum) was the most common. When the microbiota of obese mice with this higher Bacillota abundance was transplanted into the guts of germ-free mice, the germ-free mice gained a significant amount of fat as compared to those transplanted with the microbiota of lean mice with lower Bacillota abundance.^[19]

The presence of Christensenella (Bacillota, in class Clostridia), isolated from human faeces, has been found to correlate with lower body mass index.^[20]

References

External links

• Phylum "Firmicutes" - J.P. Euzéby: List of Prokaryotic names with Standing in Nomenclature