Faecalibacterium prausnitzii
Classification
Domain: Bacteria
Phylum: Firmicutes
Class: Clostridia
Order: Clostridiales
Family: Ruminococcaceae [Others may be used. Use NCBI link to find]
Species
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NCBI: Taxonomy |
Faecalibacterium prausnitzii
Description and Significance
Faecalibacterium prausnitzii is rod-shaped, non-motile, non-spore forming and is strictly anaerobic. When studied, its optimal growth temperature was revealed to be approximately 37 degrees Celsius, which parallels the temperature of the human body. Moreover, as F. prausnitzii is extremely oxygen sensitive, studies have shown that when exposed to ambient air, F. prausnitzii lose their viability within approximately 2 minutes. These attributes have led to challenges regarding the cultivation and preservation of F. prausnitzii.
F. prausnitzii colonization in the colon is considered to be a notable biomarker for a healthy human gastrointestinal tract, and plays a key role in the maintenance of overall gut homeostasis. Decreased presence of F. prausnitzii has been linked to gut inflammation and several bowel diseases, including Crohn’s disease, ulcerative colitis, and colorectal cancer.
Because of its significant role in gut homeostasis, F. prausnitzii strains are of high interest as a next-generation probiotic. Recent research has focused on additional molecules and strategies aimed at maintaining F. prausnitzii viable even when exposed to higher gradients of oxygen. There have been successful insights made that have shown F. prausnitzii to maintain its viability for 24 hours at ambient air by exploiting extracellular antioxidants such as riboflavin and cysteine, among others. This is being done in an effort to make F. prausnitzii commercially available as a biotherapeutic remedy and probiotic to help those suffering from bowel diseases. Other researchers have also seen the potential of F. prausnitzii in the agricultural industry to be used as a probiotic for cows.
Genome Structure
Faecalibacterium prausnitzii has two main phylogroups: Phylogroup I and Phylogroup II. Within these phylogroups there are different strains whose genomes have been documented in public databases with varying levels of assembly and annotation quality. When observing the genomes of Faecalibacterium prausnitzii, altogether the genome size has displayed variation, ranging from 2.68 million base pairs (Mbp) to 3.42 Mbp and having wide range of G-C% content varying from 54.9% to 63.0%. Most genomes have been constructed from draft assemblies, however one of the first strains to have a complete genome representation is F. prausnitzii strain A2-165 (Phylogroup II). This strain of F. prausnitzii has a circular genome containing 3.11 Mbp, 56.3% G-C content, 3,017 total genes, 2,790 coding genes, and 85 RNA genes.
In a study by Fitzgerald et al. (2018), 31 genomes of high-quality draft as well as complete genomes were used in a comparative genomics analysis to observe intraspecies diversity. The results displayed a high level of genome plasticity and a relatively low level of average nucleotide identity (ANI) between F. prausnitzii groups. Based on these observations, among others, Fitzgerald et al. have proposed to separate Faecalibacterium prausnitzii into two new species level taxa.
Cell Structure, Metabolism and Life Cycle
Faecalibacterium prausnitzii has irregular staining, but typically stains like a Gram-negative bacteria. However, F. prausnitzii exhibits dermis characteristics that resemble Gram-positive bacteria, for example, those in clostridial cluster IV (Clostridium leptum group). Typical Gram-negative bacteria have LPS (lipopolysaccharide) on their outer membranes, which are the ligands for the transmembrane protein, TLR4 (Toll-like receptor 4). These are not found on F. prausnitzii or other bacteria in clostridial cluster IV. This suggests that F. prausnitzii is one of the unique bacteria whose dermis structure does not necessarily align with its Gram-stain.
Furthermore, Faecalibacterium prausnitzii is an acetate-consuming and butyrate-producing bacteria. Although it is one of the most common bacteria found in the human colon, it has been revealed that F. prausnitzii needs the presence of B. thetaiotamicron, a primary acetate-producer, in order to colonize the colon. F. prausnitzii produces the short-chain fatty acid (SCFA) butyrate as a product of fermenting indigestible fiber. Butyrate serves as one of the primary energy sources for colonocytes (cells lining the colon) and is a principal molecule that works through various signaling pathways to prevent inflammation, regulate cell proliferation (cancer chemopreventative activities), and maintain the integrity of the colon epithelial mucosa.
Ecology and Pathogenesis
Habitat; symbiosis; biogeochemical significance; contributions to environment.
If relevant, how does this organism cause disease? Human, animal, plant hosts? Virulence factors, as well as patient symptoms.
References
Author
Page authored by _____, student of Prof. Jay Lennon at IndianaUniversity.
