# Clostridiaceae

The Clostridiaceae are a family of the bacterial class Clostridia, and contain the genus Clostridium.
The family Clostridiaceae (scientific name) defined by the taxonomic outline of Bergey's Manual of Systematic Bacteriology contains as its core the genus Clostridium (sensu stricto), as well as Acetivibrio, Acidaminobacter, Alkaliphilus, Anaerobacter, Caloramator, Caloranaerobacter, Coprobacillus, Dorea, Natronincola, Oxobacter, Sarcina, Sporobacter, Thermobrachium, Thermohalobacter, and Tindallia. The previous inclusion of these additional genera (as seen on the right) in a family Clostridiaceae is based for the most part because the type species of these genera are in many cases phylogenetically related to misclassified species of the genus Clostridium. However, with the exception of Anaerobacter, Caloramator, Oxobacter, Sarcina, and Thermobrachium, these genera fall outside the radiation of what can be considered the true family Clostridiaceae and are now regarded as belonging to other families within the low G + C, Gram-positive phylum.
This misclassification is the result of well-known problems of the current taxonomic structure of the traditional genus Clostridium. The phylogenetic analysis of Collins (1994) was the first large-scale comparison of 16S rRNA gene sequences of species of the genus Clostridium and related taxa. The fact that the species of the genus Clostridium did not form a monophyletic group has been shown in a number of studies in which small groups of Clostridium species had been compared as far back as 1981. The comparative study of Collins (1994) and subsequent studies can be used to conclude that more than half of the species currently assigned to this genus are in fact not closely related to the type species, C. butyricum, and from a phylogenetic standpoint should not be included in a newly defined genus Clostridium.
This extensive genetic diversity of the genus Clostridium had been shown using 23S rRNA:DNA hybridization studies back in 1975 by Johnson and Francis, but the 16S rRNA gene sequence approach revealed the actual phylogenetic relationships between the species of this genus and other genera.
The genus Clostridium currently comprises 152 validly described species in nomenclature. However, on the basis of 16S rRNA gene sequence analyses, only 73 of these fall within the radiation of the type species of the genus Clostridium.

## Subdivisions

The polyphyletic family Clostridiaceae comprises the following:
| LPSN & NCBI | 16S rRNA based LTP_10_2024 & 120 marker proteins based GTDB 09-RS220 |
| Acidaminobacter Stams & Hansen 1985 Agathobaculum Ahn et al. 2016 Alkaliphilus Takai et al. 2001 Anaeromicrobium Zhang et al. 2017 Anaeromonas Zhang et al. 2022 "Anaerophilus" Zhang et al. 2020 Anaerosolibacter Hong et al. 2015 Anaerovirgula Pikuta et al. 2006 Anoxynatronum Garnova & Zhilina 2003 "Ca. Arthromitus" Brassicibacter Fang et al. 2012 Butyricicoccus Eeckhaut et al. 2008 Caldanaerocella Diaz et al. 2004 Caldisalinibacter Ben Hania et al. 2015 Caloramator Collins et al. 1994 Caloranaerobacter Wery et al. 2001 Caminicella Alain et al. 2002 Clostridiisalibacter Liebgott et al. 2008 Clostridium Trécul 1865 ex Prazmowski 1880 Crassaminicella Lakhal et al. 2015 "Desnuesiella" Hadjadj et al. 2016 Fervidicella Ogg & Patel 2010 Fonticella Fraj et al. 2013 Fusibacter Ravot et al. 1999 Geosporobacter Klouche et al. 2007 Haloimpatiens Wu et al. 2016 Hathewaya Lawson & Rainey 2016 "Inediibacterium" Alou et al. 2017 "Intestinibacillus" Ricaboni et al. 2017 Linmingia Ming, Nanqi & Yang 2002 Lutispora Shiratori et al. 2008 Maledivibacter Li et al. 2016 Marinisporobacter Vandieken et al. 2017 Natronincola Zhilina et al. 1999 Oceanirhabdus Pi et al. 2013 Oxobacter Collins et al. 1994 Paramaledivibacter Li et al. 2016 "Ca. Petromonas" Christman et al. 2020 Proteiniclasticum Zhang, Song & Dong 2010 "Ca. Pseudobutyricicoccus" Glendinning et al. 2020 Salimesophilobacter Zhang et al. 2013 "Ca. Savagella" Thompson et al. 2012 Serpentinicella Mei et al. 2016 Sporosalibacterium Rezgui et al. 2011 Thermobrachium ngle et al. 1996 Thermohalobacter Cayol et al. 2000 Thermotalea Ogg & Patel 2009 Tindallia Kevbrin et al. 1999 "Ca. Ventrousia" Gilroy et al. 2021 Wukongibacter Li et al. 2016 Youngiibacter Lawson et al. 2014 | "Lutisporales" "Lutisporaceae" Lutispora Clostridiales "Oxobacteraceae" Oxobacter Clostridiaceae Anaeromonas Clostridium "Desnuesiella" Haloimpatiens Hathewaya Oceanirhabdus Proteiniclasticum "Ca. Savagella" Youngiibacter "Caloramatoraceae" Caloramator Fervidicella Fonticella Thermobrachium Tissierellales "Clostridiisalibacteraceae" Clostridiisalibacter VENL01 Sporosalibacterium "Caldisalinibacteraceae" Caldisalinibacter Thermohalobacteraceae Brassicibacter Caloranaerobacter Thermohalobacter "Peptostreptococcales" "Caminicellaceae" Caminicella Maledivibacter "Ca. Petromonas" Paramaledivibacter Wukongibacter "Acidaminobacteraceae" Acidaminobacter Fusibacter "Thermotaleaceae" Anaeromicrobium "Anaerophilus" Anaerosolibacter Crassaminicella Geosporobacter "Inediibacterium" Marinisporobacter Salimesophilobacter Thermotalea "Tindalliaceae" Anoxynatronum Tindallia "Natronincolaceae" Alkaliphilus Anaerovirgula Natronincola Serpentinicella "Oscillospirales" "Butyricicoccaceae" Agathobaculum Butyricicoccus "Intestinibacillus" "Ca. Pseudobutyricicoccus" "Ca. Ventrousia" |

## Phylogeny

The currently accepted taxonomy is based on the List of Prokaryotic names with Standing in Nomenclature (LPSN) and National Center for Biotechnology Information (NCBI)
| 16S rRNA based LTP_10_2024 | 120 marker proteins based GTDB 09-RS220 |
| Clostridiaceae Oxobacter Fervidicella Fonticella Clostridium cylindrosporum Caloramator species-group 2 Caloramator Thermobrachium Clostridium ~2 Clostridium ~3 Clostridium ~4 Clostridium cadaveris (Klein 1899) McClung & McCoy 1957 Youngiibacter Proteiniclasticum Clostridium ~5 Clostridium ~6 Inconstantimicrobium Clostridium ~7 Clostridium perfringens (Veillon & Zuber 1898) Holland 1920 ex Hauduroy et al. 1937 Clostridium tarantellae (Udey, Young & Sallman 1977) Lawson & Rainey 2016 Sarcina Goodsir 1842 Clostridium Trécul 1865 ex Prazmowski 1880 | Oxobacteraceae Oxobacter Collins et al. 1994 Caloramatoraceae Clostridium cylindrosporum Barker & Beck 1942 ex Andreesen, Zindel & Durre 1985 Fervidicella Ogg & Patel 2010 Fonticella Fraj et al. 2013 Caloramator species-group 2 Thermobrachium Engle et al. 1996 Caloramator Collins et al. 1994 Clostridiaceae "Ca. Dwaynesavagella" corrig. Gilroy et al. 2021 Youngiibacter Lawson et al. 2014 Proteiniclasticum Zhang, Song & Dong 2010 Clostridium AE & AU Clostridium K & AN Clostridium AT Clostridium I & S Clostridium B, C, F, G, AK, AM, AO, AS, AV & AW Haloimpatiens Wu et al. 2016 Clostridium H & AF Clostridium tepidiprofundi Slobodkina et al. 2008 Oceanirhabdus Pi et al. 2013 Clostridium collagenovorans Jain & Zeikus 1988 Hathewaya Lawson & Rainey 2016 Clostridium J & AD Clostridium X & Z "Desnuesiella" Hadjadj et al. 2016 Clostridium L Clostridium AA Inconstantimicrobium Wylensek et al. 2021 "Vallorillus" Heller 1922 Anaerobacter Duda et al. 1996 Clostridium cavendishii Bowman et al. 2010 Sarcina Goodsir 1842 Clostridium Trécul 1865 ex Prazmowski 1880 |