Citrobacter freundii

Citrobacter freundii

Scientific classification
Kingdom: Bacteria
Phylum: Gammaproteobacteria
Order: Enterobacteriales
Family: Enterobacteriaceae
Genus: Citrobacter
Species: C. freundii

Citrobacter freundii is a species of facultative. anaerobic. Gram-negative bacilli of the Enterobacteriaceae family.[1] The bacteria are long rod-shaped with a typical length of 1-5 μm.[2] Most C. freundii cells are surrounded by several flagella used for locomotion, but a few are not motile. It can be found in soil, water, sewage, food, and the intestinal tracts of animals and humans.[2] The Citrobacter genus was discovered in 1932 by Werkman and Gillen. Cultures of C. freundii were isolated and identified in the same year from soil extracts.[2]

As an opportunistic pathogen, C. freundii is responsible for a number of significant infections. It is known to be the cause of a number of nosocomial infections of the respiratory tract, urinary tract, blood, and many other normally sterile sites in patients.[3] C. freundii represents about 29% of all opportunistic infections.[3]

Surprisingly, this infectious microbe in humans plays a positive role in the environment. C. freundii is responsible for reducing nitrate to nitrite in the environment.[4] This conversion is an important and crucial stage in the nitrogen cycle. These bacteria also help in recycling nitrogen.[4]

C. freundii has also been investigated for biodegradation of tannic acid used in tanneries.[4]

For metabolism, C. freundii has an ability to grow on glycerol as the sole carbon and energy source. Within its cell, a bacterial microcompartment can be found, which is capable of processing propanediol.[5]


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  2. ^ a b c Wang, J. T.; Chang, S. C.; Chen, Y. C.; Luh, K. T. (2000). "Comparison of antimicrobial susceptibility of Citrobacter freundii isolates in two different time periods". Journal of microbiology, immunology, and infection = Wei mian yu gan ran za zhi 33 (4): 258–262.  
  3. ^ a b Whalen, J. G.; Mully, T. W.; English, J. C. (2007). "Spontaneous Citrobacter freundii Infection in an Immunocompetent Patient". Archives of Dermatology 143 (1): 124–125.  
  4. ^ a b c Puchenkova, S. G. (1996). "Enterobacteria in areas of water along the Crimean coast". Mikrobiolohichnyi zhurnal (Kiev, Ukraine : 1993) 58 (2): 3–7.  
  5. ^ Pang, A.; Warren, M. J.; Pickersgill, R. W. (2011). "Structure of PduT, a trimeric bacterial microcompartment protein with a 4Fe–4S cluster-binding site". Acta Crystallographica Section D Biological Crystallography 67 (2): 91–96.