Bacteroides thetaiotaomicronRANK: Species
TAXONOMY: Bacteroidetes/Chlorobi group -> Bacteroidetes -> Bacteroidia -> Bacteroidales -> Bacteroidaceae -> Bacteroides -> Bacteroides thetaiotaomicron
The predominance of B. thetaiotaomicron in human feces makes it a worthy candidate as a marker of human fecal matter. A bacterial primer set for it was detected in a vast majority of human feces in the study, but in only 16% of dog fecal samples, and in no cow, horse, pig, chicken, turkey, or geese samples. Since the health risk for contact with human feces is generally higher than that with non-human feces, this is an important development in terms of identifying human fecal matter. Bacteroides thetaiotaomicron is a major component of the adult intestine and has been used as a useful model for the study of human-bacterial symbiosis. Its metabolic function for humans is to degrade plant polysacharides, a very essential capability for the human gut. Additionally, it is very important during the postnatal transition between mother's milk and a diet heavily consisting of plant starches. It has been found to stimulate angiogenesis (growth of new blood vessels from pre-existing vessels) within the gut, due to a microbial signal via bacterial sensing Paneth cells. B. thetaiotaomicron benefits its host by providing sufficient absorptive ability for nutrients the microbe helps process. Another postnatal developmental process within the gut mediated by Bacteroides thetaiotaomicron is the formation of the intestinal mucosal barrier, which helps protect the host against pathogenic invasion via the regulation of the expression of species-specific protein antibiotics. The environment sensing regulatory apparatus present in B. thetaiotaomicron allows for adaptive food seeking, which stabilizes food webs, and subsequently leads to the longevity of communities. This ability to adaptively 'forage' is an area of biotechnical interest. Identified as constituent of vaginal microbiome. [PMID:23282177]
Bacteroides thetaiotaomicron is an anaerobic symbiont in the distal human intestine and has an unusually large glycobiome (the repertoire of genes involved in the acquisition and metabolism of polysaccharides. This glycobiome enables B. thetaiotaomicron to turn to host polysaccharides when dietary polysaccharides become limited. B. thetaiotaomicron not only hydrolyses host-derived glycans but also proactively determines the type of glycans that are produced by gut epithelial cells. The induction of host-derived glycans by B. thetaiotaomicron might serve an adaptive function, creating a habitable niche for itself that other glycophiles could exploit, and thereby contributing to ecosystem stability and functional diversity. These unique features have prompted the characterization of B. thetaiotaomicron as a keystone species. Another mechanism by which B. thetaiotaomicron might stabilize the microbial ecology towards a healthy host–microbiota relationship involves its ability to induce the antimicrobial peptide angiogenin, which kills opportunistic or pathogenic organisms but not B. thetaiotaomicron or other commensals. Moreover, B. thetaiotaomicron inhibits the transcription of pro-inflammatory genes through peroxisome proliferator-activated receptor-γ (PPARγ)-dependent nuclear export of the nuclear factor-κB subunit p65, thereby potentially resisting inflammatory changes that could destabilize the symbiotic microbiota. A cytotoxic T lymphocyte protein 4 (CTLA4) blockade immunotherapy was shown to depend on particular Bacteroides species (Bacteroides thetaiotaomicron and Bacteroides fragilis). Together, these results indicate that the immune response to specific members of the gut microbiota may help set the stage for cancer treatment. [PMID: 26541610]
This species has been identified as a resident in the human gastrointestinal tract based on the phylogenetic framework of its small subunit ribosomal RNA gene sequences.[PMC 4262072]
In a study of gut bacteria of 15 patients with SARS-CoV-2 over the course of hospitalization, Bacteroides dorei, Bacteroides thetaiotaomicron, Bacteroides massiliensis, and Bacteroides ovatus, which downregulate expression of ACE2 in murine gut, correlated inversely with SARS-CoV-2 load in fecal samples from patients. [PMID: 32442562] [PMCID: PMC7237927]
Anti-Ro antibodies are present in about 50% of patients with systemic lupus erythrematosis (SLE), up to 90% of patients with subacute cutaneous lupus erythematosus (SCLE), >90% of newborns with neonatal lupus erythematosus (NLE), and up to 80% of patients with Sjögren’s syndrome. Two distinct Ro antigens have been identified, Ro60 and Ro52, which differ substantially in structure and function. Although both antibodies can be found in patients with SLE, anti-Ro60 is the earliest and most common preclinical anti-nuclear antibody. In addition, anti-Ro antibodies are pathogenic, as evidenced by the trans-placental spread of these antibodies in NLE, leading to potentially fatal cardiac conduction defects and cutaneous lesions similar to SCLE.
Ro60 is highly evolutionarily conserved, with orthologs found in taxa ranging from vertebrates to bacteria, and even bacteriophages
Relevant to human biology, multiple commensal bacteria identified on the skin, oral mucosa, and gut encode Ro60 orthologs with high sequence similarity to hRo60, including certain species of Corynebacterium, Propionibacterium, and Bacteroides. Studies of the normal human gut have shown that the generation of commensal-reactive antibodies and T cell receptors (TCRs) is both abundant and physiologic. We hypothesized that autoimmune-predisposed individuals with the right combination of genetic susceptibility and environmental exposures who are chronically colonized by Ro60 commensals may develop antibodies against a bacterial Ro60 ortholog that leads to autoimmunity via cross-reactivity and epitope spreading.
The presence of the bacteria alone would not be expected to trigger autoimmunity in healthy individuals but may be a source of antigen in susceptible patients with genetic predispositions such as HLA polymorphisms that present the appropriate peptides. Despite the lack of antibodies to B. theta ribonucleoproteins, anti-Ro60positive lupus patients from two independent patient cohorts had serum antibodies that bound the BtRo60 ortholog protein. [PMID:29593104]