A Microbial Biorealm page on the genus Clostridium difficile
Higher order taxa
Bacteria; Firmicutes; Clostridia; Clostridiales; Clostridiaceae; Clostridium [Others may be used. Use  link to find]
Description and significance
C. difficile is found everywhere in nature like in water, air, human and animal feces, on most surfaces (especially in hospitals) and most prevalently in soil. C. difficile shows optimum growth when at human body temperature. C. difficile appears as long drumsticks with a bulge at each end. C. difficile was first isolated by Hall and O’Toole from the meconium and feces of newborn infants. It is important enough to have its genome sequenced because it provides a better tool for preventing and controlling infection. The genome also reveals clues as to how the pathogen thrives in the GI tract and why some strains are so much more virulent than others. The genome of C. difficile can also explain their antimicrobial resistance and allow for quicker detection and better treatment options. In addition, it allows scientists to correlate different toxins and genes and their disease-causing ability.
C. difficile Strain 630 (epidemic type X) has a single circular chromosome with 4,290,252 bp (G+C content = 29.06%) and a circular plasmid with 7,881 bp (G+C content = 27.9%). The whole genome has been sequenced and found that 11% of the genome consists of mobile genetic elements such as conjugative transposons. These elements provide C. difficile with the genes responsible for its antimicrobial resistance, virulence, host interaction and the production of surface structures. For example, the cdeA gene of C. difficile produces a multidrug efflux pump which was shown to be homologous to known efflux transporters in the multidrug and toxic compound extrusion (MATE) family. The protein facilitates energy-dependent and sodium-coupled efflux of drugs from cells. In addition, the cme gene in C. difficile has been shown to confer multidrug resistance in other bacteria.
Cell structure and metabolism
C. difficile is a gram-positive spore-forming anaerobe. It expresses two S-layer proteins one of which is highly conserved among strains and one which shows sequence diversity. Both proteins are derived from a single gene product and both are associated with amidase activity. It requires five amino acids (Leu, Ile, Pro, Trp and Val) for energy metabolism and addition of Gly increases growth significantly. C. difficile undergoes amino acid fermentation in order to create ATP as a source of energy.
C. difficile is not a major constituent of the microflora in colons of healthy adult humans or animals but can grow to large populations in people that are treated with antibiotics, especially broad-spectrum antibiotics. This is because the antibiotics kill off the normal flora of the intestines leaving C. difficile to freely grow and colonize the intestine. As long as other organisms are around C. difficile cannot grow due to limited resources and space, however, there is nothing stopping it from growing out of control in the absence of other microorganisms. When under extreme conditions such as the low pH environment of the stomach, high heat or when under attack by antibiotics C. difficile can form spores which can survive for up to two years and withstand extreme conditions. The spores can then convert to the active form of C. difficile when conditions are favorable and allow the bacteria to grow.
Overgrowth of the bacteria in the intestines of human and animal hosts leads to buildup of its toxins and their deleterious effects. It can be transferred from person to person through the fecal-oral route. Most often C. difficile is acquired nosocomially (contracted secondary to being hospitalized). C. difficile produces two virulence factors: enterotoxin (toxin A) which is found in 70% of strains and cytotoxin (toxin B) which is found in all strains. The toxins inactivate GTPases and disrupt tight junctions in the intestinal epithelial cells leading to increased paracellular permeability which leads to fluid secretion (diarrhea), mucosal injury and inflammation. Expression of C. difficile toxins A and B and their sigma factor TcdD is controlled by temperature; they become upregulated when the temperature is shifted from 22 to 37 degrees C which is an adaptation to their mammalian hosts C. difficile toxin B gets cleaved by a factor in the eukaryotic target cell thereby permitting its cellular uptake. Patient symptoms with C. difficile intestinal infections include diarrhea, inflammation, fever and abdominal pain. C. difficile is the primary causative agent of pseudomembranous colitis which involves many of the above mentioned systems.
Application to Biotechnology
Does this organism produce any useful compounds or enzymes? What are they and how are they used?
Enter summaries of the most recent research here--at least three required
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Lebel, S., Bouttier, S., Lambert, T. “The cme gene of Clostridium difficile confers multidrug resistance in Enterococcus faecalis”. FEMS Microbiology Letters 238 (1), 93–100.
Dridi, L., Tankovic, J., Petit, J. “CdeA of Clostridium difficile, a New Multidrug Efflux Transporter of the MATE family”. Microb Drug Resist. 2004 Sept;10(3):191-6.
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Edited by Shaheen Najafi student of Rachel Larsen and Kit Pogliano