Solobacterium moorei

Cell structure and molecular components

Solobacterium moorei is a non-motile, rod-shaped bacterium approximately 0.2 μm in width and 0.4-0.7 μm in length. It is frequently found in pairs or chains without flagella.

Solobacterium moorei have hydrophobic adhesins to attach to the lipophilic molecules of oral epithelial cells. These adhesins allow them to form biofilms and contribute to halitosis. Green tea extract, containing epigallocatechin-3-gallate (EGCG), inhibits S. moorei biofilm formation and reduces its ability to attach to oral epithelial cells.

Genetic composition

The sequenced genome of S. moorei is a single linear chromosome spanning 2,615,268 base pairs with a GC content of 37.2%.

Metabolism and molecular pathways

Most strains can ferment fructose, galactose, glucose, maltose, and ribose and hydrolyze esculin. They exhibit α-galactosidase and α-glucosidase activity to catalyze the breakdown of carbohydrates into simpler sugars. S. moorei produces acetic acid in glucose fermentation and volatile sulfur compounds (VSCs) in anaerobic respiration. Additionally, β-Galactosidase activity is present in the bacterium, which is directly associated with oral malodor when present in the saliva due to volatile compound release.

Solobacterium moorei likely has a homolog of the Methionine Gamma-Lyase (MegL) enzyme, which can produce hydrogen sulfide. This enzyme acts as a catalyst to degrade amino acids containing sulfur, leading to the formation of volatile sulfur compounds.

Pathogenesis

Solobacterium moorei is an opportunistic pathogen, and infections outside of halitosis are often observed in patients with cancer or a suppressed immune system. This pathogen has contributed to bloodstream and wound infections, with bacteremia as the most frequently reported infection caused by S. moorei. Osteoarticular and skin and soft tissue infections (SSTIs) have also been reported in association with this bacteria.

Tumor cell signaling

High concentrations of S. moorei were found in colorectal adenomatous polyp tissue, which positively correlated with inflammation in the region. Research suggests this bacteria promotes the disruption of the intestinal barrier and progression of adenomatous polyps due to inflammation, a risk factor for colorectal cancer.

Solobacterium moorei attached to HT-29 colorectal cancer cells and stimulated cell proliferation. This bacteria promotes colorectal cancer growth by binding to integrin α2 and integrin β1 on tumor cells through its Cna B-type domain-containing protein. This activates the PI3K-AKT-mTOR-C-myc signaling pathway via phosphorylated Focal Adhesion Kinase (phospho-FAK), leading to tumor progression due to promotion of cell survival and reduction of cell apoptosis. Small interfering RNA (siRNA) was used to silence the genes integrin α2 and integrin β1, reducing the expression of the integrin subunits. Blocking integrin α2/β1 stopped S. moorei's cancer-promoting effects in lab and mice studies.

Identification techniques

Solobacterium moorei is a slow-growing bacterium and is difficult to cultivate. Traditional bacterial phenotypic testing cannot identify this bacterium accurately. The only truly reliable method to recognize this bacterium is 16S rRNA gene sequencing; however, Matrix-Assisted Laser Desorption/Ionization-Time of Flight Mass Spectrometry (MALDI-TOF MS) is a more accessible method. Additionally, DNA probe assays can detect S. moorei strains.

References

References

1. (2000). "Phylogenic and phenotypic characterization of some Eubacterium-like isolates from human feces: description of Solobacterium moorei Gen. Nov., Sp. Nov". Microbiology and Immunology.
2. D.S. Gerber, DS, Haraszthy, VI, Zambon, JJ. (2007). [http://iadr.confex.com/iadr/2007orleans/techprogram/abstract_90579.htm Characterization of ''Solobacterium'' moorei Strains from Subjects with Halitosis] {{webarchive. link. (2007-03-14, IADR/AADR/CADR 85th General Session and Exhibition (March 21–24, 2007))
3. Rauscher, Megan. (2008-04-07). "Scientists find bug responsible for bad breath".
4. (2020-10-01). "Small, but smelly: the importance of Solobacterium moorei in halitosis and other human infections". Heliyon.
5. (2010-01-13). "Phenotypic and molecular characterization of Solobacterium moorei isolates from patients with wound infection". Journal of Clinical Microbiology.
6. (2000). "Phylogenic and phenotypic characterization of some Eubacterium-like isolates from human feces: description of ''Solobacterium moorei'' Gen. Nov., Sp. Nov". Microbiology and Immunology.
7. (2020-10-01). "Six cases of Solobacterium moorei isolated alone or in mixed culture in Hungary and comparison with previously published cases". Anaerobe.
8. (2020-10-01). "Six cases of Solobacterium moorei isolated alone or in mixed culture in Hungary and comparison with previously published cases". Anaerobe.
9. (2020-10-01). "Small, but smelly: the importance of Solobacterium moorei in halitosis and other human infections". Heliyon.
10. (2015-03-10). "Green tea extract and its major constituent epigallocatechin-3-gallate inhibit growth and halitosis-related properties of Solobacterium moorei". BMC Complementary and Alternative Medicine.
11. (2023-11-29). "Complete genome sequence of Solobacterium moorei JCM 10645T isolated from a human stool sample". Microbiology Resource Announcements.
12. (2011-07-01). "Solobacterium moorei Bacteremia: Identification, Antimicrobial Susceptibility, and Clinical Characteristics". Journal of Clinical Microbiology.
13. (2022-03-01). "Relationships between Solobacterium moorei and Prevotella intermedia in subgingival microbiota of periodontitis patients with halitosis: A preliminary study using qPCR". The Saudi Dental Journal.
14. (2021-07-01). "Salivary β-glucosidase as a direct factor influencing the occurrence of halitosis". Biochemistry and Biophysics Reports.
15. (2021-06-05). "A New Look at the Genus Solobacterium: A Retrospective Analysis of Twenty-Seven Cases of Infection Involving S. moorei and a Review of Sequence Databases and the Literature". Microorganisms.
16. (2024-02-17). "Solobacterium moorei promotes the progression of adenomatous polyps by causing inflammation and disrupting the intestinal barrier". Journal of Translational Medicine.
17. (2025-01-27). "Solobacterium moorei promotes tumor progression via the Integrin α2/β1-PI3K-AKT-mTOR-C-myc signaling pathway in colorectal cancer". International Journal of Biological Sciences.
18. (2020). "Isolation and identification methods for Solobacterium moorei involved in halitosis". Journal of the Japanese Society of Oral Examination.