Corynebacterium glutamicum characteristics, morphology, culture

4606
Abraham McLaughlin

Corynebacterium glutamicum It is a bacterium in the form of a rod, Gram positive, facultative anaerobic and present in the soil. It is neither spore-forming nor pathogenic. Along with the rest of the Corynebacteriaceae and the bacteria of the Mycobacteriaceae and Nocardiaceae families, it is part of the group known as the CMN group. This group includes many bacteria of medical and veterinary importance..

The bacteria C. glutamicum It is widely used in industry for the production of amino acids. The use of this bacterium for industrial production dates back more than 40 years. 

Corynebacterium glutamicum. Photo by AJC1 Flickr. Taken and edited from https://www.acercaciencia.com/2013/05/16/germenes-con-caracteristicas-humanas/corynebacterium-glutamicum-by-ajc1-flickr/

The amount of amino acids produced by these bacteria, including monosodium glutamate and L-lysine, currently exceeds 100 tons per year.

Article index

  • 1 General characteristics
  • 2 Taxonomy
  • 3 Morphology
  • 4 Cultivation
  • 5 Pathogenesis
  • 6 Uses in biotechnology
    • 6.1 Production of amino acids
    • 6.2 Other products and applications
  • 7 References

General characteristics

-Corynebacterium glutamicum is a non-pathogenic Gram positive bacteria.

-Does not produce spores.

-Contains catalase.

-It breaks down carbohydrates through its fermentative metabolism.

-It is capable of synthesizing amino acids such as serine, glutamate and lysine.

Taxonomy

The species C. glutamicum was first discovered in Japan and described by Kinoshita et al. in 1958, under the name of Micrococcus glutamicus. Later (1967), Abe et al. Relocated it to the genre Corynebacterium.

Bacteria of the genus Corynebacterium they are taxonomically located in the suborder Corynebacterineae. This suborder in turn belongs to the order Actinomycetales, class Actinobacteria.

The suborder Corynebacterineae includes the families Corynebacteriaceae, Mycobacteriaceae and Nocardiaceae referred to as the CMN group. Corynebacterium belongs to the first of these families.

Morphology

The bacteria are rod-shaped with swollen ends in the shape of a mallet or club. It has a chromosome and a circular plasmid. Its genome consists of 3,314,179 nucleotides.

The cell wall is composed, among other substances, of a layer of peptidoglycan, short-chain mycolic acids, meso-diaminopimelic acids and arabino-galactan polymers..

Culture

Corynebacterium glutamicum uses a wide variety of substrates, including sugars, organic acids and alcohols, for its growth and the production of amino acids.

This bacteria break down carbohydrates through the fermentation process. Amino acid production is influenced by the given carbon source and by certain supplementation conditions such as biotin limitation.

To obtain the inocula, culture media of tryptone complexes (YT), yeast extract and modified minimal media of CGXII have been used..

For cultivation, temperatures of 30 ° C and a pH of 7.4 - 7.5 are recommended. The carbon sources, as well as the substances that are going to be used to enrich the crop, will depend on the results to be obtained..

For example, glucose, ammonium sulfate, magnesium sulfate, and dipotassium phosphate have been found to have a significant influence on succinate production..

To obtain a high concentration of L-lysine, the culture medium must have glucose, ammonium sulfate, calcium carbonate, bactocasamino acid, thiamine hydrochloride, D-biotin, potassium dihydrogen phosphate, magnesium sulfate heptahydrate, ferrous sulfate heptahydrate and manganese chloride tetrahydrate.

Corynebacterium glutamicum, Photo by Carlos Barreiro. Taken and edited from http://www.dicyt.com/viewItem.php?itemId=14535

Pathogeny

Although most of the bacteria belonging to the Corynebacteriaceae family are pathogenic, some of them, including C. glutamicum, they are harmless. The latter, known as non-diphtheria corynebacteria (CND), are commensals or saprophytes that can be present in humans, animals and the soil..

Some CND, such as C. glutamicum Y C. feeiciens, are used in the production of essential amino acids and vitamins.

Uses in biotechnology

The genome of C. glutamicum it is relatively stable, grows rapidly, and does not secrete extracellular protease. In addition, it is non-pathogenic, does not form spores, and has relatively low growth requirements..

These characteristics, and the fact that it produces enzymes and other useful compounds, have allowed this bacterium to be called a “workhorse” in biotechnology..

Production of amino acids

The first product found that was known to be biosynthesized by C. glutamicum it was glutamate. Glutamate is a nonessential amino acid present in about 90% of synapses in the brain.

It is involved in the transmission of information between the neurons of the central nervous system and in the formation and recovery of memory.

Lysine, an essential amino acid for humans and which is part of the proteins synthesized by living beings, is also produced by C. glutamicum.

Other amino acids obtained from this bacterium include threonine, isoleucine, and serine. Threonine is used mainly to prevent the appearance of herpes.

Serine helps in the production of antibodies and immunoglobulin. Isoleucine, for its part, is involved in protein synthesis and energy production during physical exercise..

Other products and applications

Pantothenate

It is the most active form of vitamin B5 (pantothenic acid), as calcium pantothenate is used as a supplement in diets. Vitamin B5 is essential in the synthesis of carbohydrates, lipids and proteins.

Organic acids

Among others, C. glutamicum produces lactate and succinate. Lactate has multiple applications, such as fabric softener, food acidity regulator, leather tanning, purgative, among others..  

Succinate, for its part, is used for the production of lacquers, colorants, perfumes, food additives, medicines and for the manufacture of biodegradable plastics.

Alcohols

Because it ferments sugars, it is capable of producing alcohols, such as ethanol and isobutanol. For this reason there are trials for the synthesis of ethanol in cultures of  C. glutamicum from waste from sugar cane. The objective of these tests is to achieve the industrial production of biofuels.

Xylitol, a polyol, or sugar alcohol, is used as a sweetener for diabetics as it does not raise blood sugar levels.

Bioremediation

C. glutamicum it contains two operons in its genome, called ars1 and ars2, which are resistant to arsenic. There are studies in progress in order to eventually use this bacterium to absorb arsenic from the environment..

Biodegradable plastics

In addition to succinate, an organic acid produced naturally by bacteria, useful for the production of biodegradable plastics, there is another possible compound that can be used for these purposes..

This compound is a polyester called poly (3-hydroxybutyrate) (P (3HB)). P (3HB) is not produced naturally by  C. glutamicum. However, genetic engineers have carried out studies to create in the bacterium, by genetic manipulation, a biosynthetic pathway that allows its production.

References

  1. S. Abe, K.-I. Takayama, S. Kinoshita (1967). Taxonomical studies on glutamic acid-producing bacteria. The Journal of General and Applied Microbiology.
  2. J.-Y. Lee, Y.-A. Na, E. Kim, H.-S. Lee, P. Kim (2016). The actinobacterium Corynebacterium glutamicum, an Industrial workhorse. Journal of Microbiology and Biotechnology.
  3. J. Lange, E. Münch, J. Müller, T. Busche, J. Kalinowski, R. Takors, B. Blombach (2018). Deciphering the adaptation of Corynebacterium glutamicum in transition from aerobiosis via microaerobiosis to anaerobiosis. Genes.
  4. S. Wieschalka, B. Blombach, M. Bott, B.J. Eikmanns (2012). Bio-based production of organic acids with Corynebacterium glutamicum. Biotechnology.
  5. M. Wachi (2013). Amino acids exporters in Corynebacterium glutamicum. In: H. Yukawa, M. Inui (Eds.) Corynebacterium glutamicum biology and biotechnology.
  6. Corynebacterium glutamicum. On Wikipedia. Retrieved on September 25, 2018 from en.wikipedia.org.
  7. Corynebacterium glutamicum. On Microbe Wiki. Retrieved on September 25, 2018 from microbewiki.kenyon.edu.

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