Cloacibacillus porcorum

Cloacibacillus porcorum is a Gram-negative, anaerobic, mesophilic, non-motile, and curved rod-shaped bacterium.^[5] Its taxonomic classification includes the domain Bacteria, phylum Synergistetes, class Synergistia, order Synergistales, family Synergistaceae, genus Cloacibacillus, and species C. porcorum.^[4] Phylogenetically, C. porcorum, designated as strain CL-84, is closely related to other members of the Cloacibacillus genus, such as Cloacibacillus evryensis, which shares similar metabolic pathways and a high similarity of 95% in genome sequencing.^[5] It also shows a 90% similarity to Synergistes jonesii, which is another related species within the Synergistetes phylum.^[5]

Cloacibacillus porcorum was first isolated and reported in 2013 by researchers, Looft, Levine, and Stanton.^[5] Strain CL-84, or later classified as C. porcorum, was isolated and identified, along with seven other Synergistetes strains, from the mucosal lining of a pig caecum from Ames, Iowa, United States.^[5] The organism was identified through various methods, including analysis of its 16S rRNA gene sequence, examination of its cellular fatty acid composition, measurement of its DNA's G+C content, and evaluation of its metabolic byproducts.^[6]

Cloacibacillus porcorum has a curved-rod shape, typically measuring 0.8–1.2 μm wide and 3.5–5.0 μm long.^[5] The bacterium possesses a thin peptidoglycan layer encompassed by an outer membrane, a defining feature of Gram-negative bacteria.^[5] This was confirmed through Gram staining and transmission electron microscopy (TEM), two common methods for visualizing bacterial structures.^[5] Notable characteristics of C. porcorum include its classification as non-motile as well as its inability to form spores or inclusion bodies.^[5] When grown under anaerobic conditions on BHIAH agar at 39 °C, colonies of C. porcorum are shiny and small (1 mm wide) and mostly clear, with a brown tint.^[5]

C. porcorum has the following fatty acid profile:

• iso-C15:0 (about 27%) – 13-Methyltetradecanoic acid, which helps the cell stay stable in its environment.^[7]
• iso-C15:0 3-OH (15%) – 3-Hydroxy-13-methyltetradecanoic acid, a branched hydroxy fatty acid which may affect how the cell interacts with water.^[8]
• iso-C17:0 (12%) – 15-Methylhexadecanoic acid, a slightly longer branched fatty acid that contributes to membrane flexibility and adaptation to anaerobic environments.^[9]
• C16:0 (10%) – palmitic acid, a straight-chain saturated fatty acid that plays a structural role in the lipid bilayer.^[10]
• Additional fatty acids in small quantities.^[5]

The genome of C. porcorum (strain CL-84ᵀ) was first sequenced as part of a broader study on swine intestinal microbes.^[5] The bacterium has a DNA G+C content of 55.1 mol% which is characteristic of its classification as a member of the phylum Synergistetes.^[5] The gyrB sequence, a conserved genetic marker, of strain CL-84ᵀ showed only 90% similarity to that of Cloacibacillus evryensis which highlights its classification as a distinct species within the genus.^[5]

C. porcorum’s 16S rRNA gene sequence is approximately 1447 base pairs long and it shares 95% similarity with C. evryensis and 90% with “Synergistes jonesii”.^[5] C. porcorum forms a distinct lineage within the genus Cloacibacillus and it clusters closely with uncharacterized Synergistetes isolates from human tissue, according to phylogenetic analyses using neighbor-joining, maximum parsimony, and maximum-likelihood methods.^[5]