Corynebacterium efficiens

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A Microbial Biorealm page on the genus Corynebacterium efficiens


Higher order taxa

Cellular organisms; Bacteria; Actinobacteria; Actinobacteria (class); Actinobacteridae; Actinomycetales; Corynebacterineae; Corynebacteriaceae; Corynebacterium; Corynebacterium efficiens


NCBI: Taxonomy

Corynebacterium efficiens

Description and significance

Monosodium Glutamate is today mired in controversy as both a unique flavor enhancer and potential cause of human neurologic disorders.[1] As sides spar over this issue, the reality is production of L-gluatamine aka l-gln (the pre-cursor amino acid to MSG) is in excess of 1 million tons.[2] For many companies, the choice method of l-gln production is via fermentation of sugars by microorganisms. Most notable, are the microbes of the genus Corynebacterium. Species exploited for commercial production of l-gln have been Corynebacterium glutamicum and Corynebacterium callunae.[2,3] Ajinomoto, a Clinical Research Laboratory in Japan, have isolated three unique strains proven to be more efficient in l-gln production. (The details will be described in Biotech section) These three strains have been phylogenetically identified as a unique species of Corynebacterium, and are collectively named Corynebacterium efficiens.[2]

C. efficiens are gram-positive, non-motile cells. The isolates used to determine this new species were obtained from onion bulbs and soils of Kanagawa, Japan.[2] Grown on agar plates, the isolates are best grown between 30 and 40° C and appear as yellow, smooth, circular colonies.[2] As “coryneform” is literally translated to “club-shaped rods” in Greek, individual c. efficiens cells present as V-shaped rods caused by a “snapping” action during cell division.[2,4] C. efficiens is grown aerobically on simple media with glucose as the primary carbon source.

C. efficiens is of specific interest to companies involved in commercial production of amino acids because of its thermostability. The effectiveness of this species’ ability to grow efficiently at high temperatures has led to current genome sequencing to understand the genomic characteristics contributing to this organism’s thermostability. Scientists believe the key underlying c. efficiens thermostability will be invaluable for the development of thermostable protein synthesis.

Genome structure

C. efficiens has a single circular chromosome of approximately 3,147,090 bp and two plamids 23,743 bp and 48,672 bp in length.[2,5] The chromosome has a G+C content of 63% and the plasmids have a G+C content of 54% and 56%. This high G+C content is thought to play a factor in the thermostability of the organism.[2] The average Open Reading Frame for the chromosome is 981 bp. The average ORF for Plasmid 1 is 1,155 bp and plasmid 2 is 924 bp.

The genome structure plays an important role in identification of this specific species. Comparing 16S rDNA genome sequences of c. efficiens vs. the Corynebacterium genus reveal that the isolates of C. efficiens belong to the “glutamic-acid producing species".[2,6] Of these acid producing species, c. efficiens was 95.3 % similar to c. glutamicum. This is lower than the criteria used to define identical bacterial species (97%).[2] The importance of high G+C content will be discussed in “Cell structure and Metabolism”

C. efficiens genetic data is obtained from bacterial strain YS-314 [2]

Cell structure and metabolism

Hallmark to c. efficiens is its distinctive ability to produce l-gln at higher temperatures. Prior to c. efficiens identification, the microbe of choice for commercial production of l-gln is c. glutamicum. This species produce amino acid and grow effectively at a top temperature of ~30° C. C. efficiens has been found to grow and produce acid at 45° C.[2,7] The benefit of this advantage will be discussed in “application to biotechnology”. Comparative analysis of c. efficiens and other mesophilic corynebacterium (c. glutamicum & c. diphtheriae) reveal unique amino acid characteristics of c. efficiens proteins.[7] As mentioned above, c. efficiens has a higher G+C content which immediately indicate a higher “melting” temperature for DNA strands. Furthermore, studies have found that compared to c. glutamicum, c. efficiens has general amino acid substitutions throughout its proteins and cell structures. Notably arginine for lysine, and alanine/threonine for serine.[7] These amino acid substitutions correlate to protein thermostability as Arg maintains ion pairs more easily, and Ala/Thr strengthen hydrophobic interactions leading to stronger β-sheets for proteins.[7]

As mentioned many previously, c. efficiens is highly lauded for its ability to produce the amino acid l-glutamine. It produces this amino acid optimally when cultured aerobically at 45° C (in presence of 6% glucose).[2] It has been found that production also occurs with carbon sources such as fructose, mannose, ribose, maltose and dextrin. C. efficiens does NOT produce acid from xylose, mannitol, lactose, strarch or glycogen.[2]

Regarding nitrogen metabolism, studies have found certain gene clusters for nitrate uptake systems that indicate c efficiens is better equipped for anaerobic nitrate and nitrite respiration compared to C. glutamicum.[10]


C. efficiens is a soil living species. This habitat confers with studies that have found that C. efficiens along with fellow soil-living species C. glutamicum exhibit a broader spectrum of genes for nitrogen transport and metabolism compared to the PATHOGENIC species C. diphtheriae and C. jeikeium.[10] The three specific isolates used to identify C. efficiens were isolated from onion bulbs and soils of Kanagawa, Japan. It is believed that C. efficiens along with other soil-dwelling corynebacteria play primary roles in nitrogen levels of soil and atmosphere.[8]

As some Corynebacterium forms have been found to be pathogenic, it is apparent there is a diverse range of environments ‘’corynebacterium’’ can develop. The thermostability of c. efficiens for example, demonstrate the high adapatability of Corynebacterium.

Comparing c. efficiens genomically to c. glutamicum and c. diptheriae demonstrate thermoadaptability. C. diptheriae is not considered a glutamic acid producing strain and was found to be MORE closely related to C. glutamicum rather than C. efficiens. This suggests that C. glutamicum is closer to the ancestral genome strucure of Corynebacterium and C. efficiens must have acquired thermostability through divergence from sister species.[7] Thus allowing C. efficiens to grow in habitats of higher temperature.[8]


How does this organism cause disease? Human, animal, plant hosts? Virulence factors, as well as patient symptoms.

Application to Biotechnology

Does this organism produce any useful compounds or enzymes? What are they and how are they used?

Current Research

Enter summaries of the most recent research here--at least three required


[Sample reference] Takai, K., Sugai, A., Itoh, T., and Horikoshi, K. "Palaeococcus ferrophilus gen. nov., sp. nov., a barophilic, hyperthermophilic archaeon from a deep-sea hydrothermal vent chimney". International Journal of Systematic and Evolutionary Microbiology. 2000. Volume 50. p. 489-500.

Edited by student of Rachel Larsen