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Bacillus fragilis

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A gram-negative rod shape non-motile anaerobes involved in various metabolic activities as a normal flora inside the colon or intestine in human and animals.


Bacillus fragilis is very useful as long as it remains inside the colon or lumen since it can utilized diverse simple sugars and many complex pathway necessary for generation of energy like synthesis of lipids, carbohydrates and fatty acids. During infection it is implicated in abscess formation wherein this bacterium formed afibrous membrane surrounding the infected site and if left untreated can caused major damage in human and animals.

Bacillus fragilis has been reclassified into separate species due to its distinct DNA homology with a size larger than Escherichia coli and has a large vacuoles that contains enormous capsule with no cell membrane endotoxin to limit pathogenicity and peptidoglycan layer. It makes up at least 2% of the normal flora in the body accountable for at most 80% of anaerobic infections.

Bacillus fragilis is commonly isolated from pleural fluid, blood, peritoneal fluid, wounds and brain abscesses and normally lives in colon and intestines of humans as well as in animals along with Escherichia coli. These bacteria competes with other microorganisms in the lumen for nutrients and food which in turn beneficial to human body since it decreases the availability of nutrients for some dangerous pathogenic organisms to grow causing harmful infections.

Scientific classification:

Kingdom: Bacteria
Phylum: Bacteroidetes
Class: Bacteroidetes
Order: Bacteroidales
Family: Bacteroidaceae
Genus: Bacteroides
Species: Bacteroides fragilis

See also: