User:Ghkim22/Cetobacterium somerae

Taxonomy: Cetobacterium somerae traces from a unique lineage. The taxonomic classification is as follows: Bacteria, Fusobacteriota, Fusobacteriia, Fusobacteriales, Fusobacteriaceae, Cetobacterium, and lastly, Cetobacterium somerae (Cetobacterium Somerae, n.d.). The paper that records the discovery of this species describes that the closest species is Cetobacterium ceti, the only other species within the genus Cetobacterium. The sequence similarity shared with Cetobacteium ceti is 98% (Finegold et al., 2003). Leptotrichia buccalis, Sebaldella termitidis, Sneathia sanguinegens, Streptobacillus moniliformis, Propionigenium species, Ilyobacter species, and Fusobacterium species were among the other species that shared phylogenetic relationships with Cetobacterium somerae (Finegold et al., 2003). Of these, Fusobacterium species has the most sequence similarity, at 93%, while Sneathia sanguinegens has the lowest, at 82% (Finegold et al., 2003).

Discovery Process: From 2000 to 2002, in the VA Medical Center West Los Angeles and UCLA School of Medicine, a team of researchers led by Sydney M. Finegold discovered the species Cetobacterium somerae (Finegold et al., 2003). At Rush Children's Hospital in Chicago, two children between 47-51 months old with late-onset autism on oral vancomycin medication had four strains of an unknown “microaerotolerant, gram-negative, [and] rod-shaped bacterium” from their feces (Finegold et al., 2003, p. 1). Phenotypic characterization including biochemical tests, cellular fatty acid analysis, and antibiotic susceptibility testing was performed on the isolates by Finegold's team (Finegold et al., 2003). To dilute the stool samples, they were combined under anaerobic circumstances with peptone broth (Finegold et al., 2003). Plates of diluted samples were placed on different media and incubated with particular gas conditions (Finegold et al., 2003). Standard tests and commercial systems were used to evaluate biochemical parameters and measure bile sensitivity (Finegold et al., 2003). Acid production and substrate utilization were investigated (Finegold et al., 2003). Cellular fatty acids and DNA G + C concentration were examined for chemotaxonomy in species identification (Finegold et al., 2003). Using 16S rRNA gene sequencing, database searches, and relatedness-based tree construction were all part of the phylogenetic analysis process (Finegold et al., 2003). An evaluation of the groupings' stability was conducted using maximum parsimony and bootstrap analysis (Finegold et al., 2003). Both maximum parsimony and bootstrap analyses are performed specifically for examining phylogenetic trees. Maximum parsimony is an approach to minimize the number of evolutionary steps required to allot data onto branches of a phylogenetic tree (Kannan & Wheeler, 2012). On the other hand, bootstrap analyses are a method to determine the confidence intervals for a phylogenetic tree (Soltis & Soltis, 2003). 16S rRNA gene sequencing and phylogenetic analysis showed the isolates represented a novel species within the genus Cetobacterium, distinct from but closely related to Cetobacterium ceti (Finegold et al., 2003). Based on the phenotypic and phylogenetic evidence, the researchers proposed in 2003 to classify the new bacterium as Cetobacterium somerae, naming the type strain WAL 14325T (Finegold et al., 2003).

Cetobacterium somerae is also found to be in the intestinal tracts of freshwater fish. A group of researchers from Japan in 2008 used fishing sampling locations such as the Fisheries Research Laboratory of the Saitama Prefectural Agriculture and Forestry Research Center to isolate anaerobic bacteria from the intestine contents of various freshwater fishes like goldfish, tilapia, catfish, common carp and grass carp (Tschuiya et al., 2008). Standard anaerobic culture techniques on various media like Fusobacterium modified agar, Bacteroides agar and fradiomycin-Clostridium welchii agar were used (Tschuiya et al., 2008). Phenotypic characterization such as biochemical tests, fermentation products, G+C content, and 16S rRNA gene sequencing were used to identify the microbial strains (Tschuiya et al., 2008). They identified these previous "Bacteroides type A" isolates as actually being Cetobacterium somerae based on their analyses (Tschuiya et al., 2008, p. 1).

Metabolism: In 2023, a published study recorded the first bacteremia case involving Cetobacterium somerae for necrotizing cholecystitis, a condition concerning the inflammation of the gallbladder, in a human patient (Arakawa et al., 2023). The study describes that Cetobacterium somerae cannot grow in the presence of oxygen and relies on anaerobic respiration (Aarakawa et al., 2023). Through the fermentation of carbohydrates, it yields large amounts of acetate and only trace amounts of propionate and butyrate (Arakawa et al., 2023). It has been proposed to increase fish's intestinal consumption of carbohydrates by producing acetate (Arakawa et al., 2023). It can synthesize vitamin B12, which could "promote fish health” (Arakawa et al., 2023, p. 906). Ceterobacterium somerae was originally discovered in 2003 while treating children with autism with oral vancomycin (Finegold et al., 2003). It makes up 70% of the gut bacteria of several freshwater fish species, including tilapia, bass, bluegill, and carp (Arakawa et al., 2023). It's not known to cause infections in fish, but it seems to be a potentially mutualistic bacteria in fish intestines (Arakawa et al., 2023).