Bacteroides fluxus

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Higher order taxa

Bacteria; Bacteroidetes; Bacteroidetes; Bacteroidales; Bacteroidaceae; Bacteroides


Bacteroides fluxus is a newly recognized bacterium that is part of the diverse human gastrointestinal microbiome, and the GI microbiome of some other mammalians. The strain of B. fluxus that was isolated from human feces is known as YIT 12057. The short lived life span of this bacterium during observation led to the nomenclature of B. fluxus.

Description and significance

Bacteroides fluxus is an obligately anaerobic, gram stain negative cell that is non-motile, non-spore forming, and rod shaped, measuring 1.0 – 1.4 μm wide and 1.0 – 2.5 μm long. The major fatty acids that make up B. fluxus are anteiso-C15: 0, summed feature 11 (comprising iso-C17: 0 3-OH and/or C18: 2 dimethylacetal), C18: 1ω9c and iso-C15: 0 and the primary respiratory quinones are Mk-10 and Mk-11. The guanine-cytosine content is 45.2 mol%. The 16s rRNA gene sequence of B. fluxus is a 95.0% match to B. uniformis. B. fluxus incubated on GAM agar appear as opaque, whitish gray, circular and domed colonies with butter like texture and a shiny sheen. The identification and 16s rRNA gene sequencing led to the identification of B. fluxus clones in other fecal samples that were uncultured. The frequency in which B. fluxus appears in other fecal samples is indicative that B. fluxus is a common organism found in the GI tract.

The gastrointestinal microbiome has an important impact on health and wellness and disease. While the specifics of the symbiotic relationship between the GI tract and the bacteria are currently poorly understood, researchers are workings towards increasing our understanding of how the GI and the organisms interact. Researchers not only want to identify the organisms and their functions that exist in the GI tract, they want to understand how these organisms affect the physiology of the gut and effect the overall health and wellness as well as disease prevalence.

Cell Metabolism

B. fluxus is an obligate anaerobe. Glucose, galactose, fucose, arabinose, mannitol, rhamnose, and trehalose are external carbon sources for metabolism. There are also several sugar alcohols B. fluxus metabolizes like glycerol, salicin, and sorbitol. The waste products created from fermentative metabolism are succinic acid and acetic acid.

Current Research

Current research is trying to determine what the extent of the mutualistic relationship between host and the GI microbiome, and how this relationship correlates or causes disease. Determining how the microbiota influences host health and wellness, implications in disease etiology, and effect of microbiota on drug metabolism, toxicity and efficacy is a significant subject of research. While researchers know there is a significant importance of the interactions between the microbiome and the host, the physiology is not understood. Increasing our understanding of normal human gut microbiome will lead to understanding abnormal gut micbrobiome and correlations and causations of disease.


Watanabe, Y., Nagai, F., Morotomic, M., Sakon, H., and Tanaka, R. “”Bacteroides clarus sp. nov., Bacteroides fluxus sp. nov. and Bacteroides oleiciplenus sp. nov., isolated from human faeces”. “International Journal of Systematic and Evolutiony Microbiology”. 2010. Volume 60. p. 1864-1869.

Wu, G. and Lewis, J. “”Analysis of the Human Gut Microbiome and Association With Disease”. “Clinical Gastroenterology and Hepatology”. 2013. Volume 11. p. 774-777.

Edited by (Samantha Nicholas), student of Rachel Larsen at the University of Southern Maine