Leuconostoc

from Wikipedia, the free encyclopedia
Leuconostoc
Systematics
Domain : Bacteria (bacteria)
Department : Firmicutes
Class : Bacilli
Order : Lactic acid bacteria (Lactobacillales)
Family : Leuconostocaceae
Genre : Leuconostoc
Scientific name
Leuconostoc
Van Tieghem 1878

Leuconostoc is a genus of gram-positive bacteria in the Leuconostocaceae family, which belongs to the order of the Lactobacillales (lactic acid bacteria). Leuconostoc species are widespread in the natural environment and playan important rolein various industrial and food fermentations .

features

Appearance

Most species appear as cocci in liquid culture : the cell shape is round to oval. The cells occur individually, as diplococci and as short chains of cocci. In the Gram stain they behave gram-positive, have no flagella for active movement and do not form persistence forms such as endospores . Their appearance in the light microscope is similar to the representatives of the genus Lactococcus , however, the spherical cells typical of cocci are not predominant in Leuconostoc , but rather oval or ovoid ("egg-shaped") cell shapes can be observed.

The generic name can be traced back to the appearance of the colonies ( leukos from ancient Greek means "bright" or "clear").

Growth and metabolism

As typical representatives of lactic acid bacteria , they grow anaerobically , but aerotolerantly, i.e. that is, they grow in the presence of atmospheric oxygen, but do not need oxygen for their metabolism . They are catalase negative and oxidase negative. However, they are able to form cytochromes when cultured on nutrient media containing heme or blood . In this case they show a positive reaction in the oxidase test. Another characteristic of lactic acid bacteria is the need for complex growth factors and amino acids during cultivation.

A heterofermentative lactic acid fermentation is carried out under aerobic , anaerobic and microaerophilic conditions . D - glucose or D - fructose are converted to an equimolar amount of D - lactic acid , ethanol and carbon dioxide via the pentose phosphate route . Only some species of the genus are able to break down lactose (milk sugar) in this way. For this purpose, the disaccharide lactose is split into the two components glucose and galactose with the help of the bacterial enzyme β-galactosidase . On the other hand, L - arabinose , D - mannose and maltose are among the carbohydrates that can be used by most Leuconostoc species.

All species can also break down sucrose , typical is the formation of dextrans from the sucrose substrate . Through the formation of dextrans, solutions containing sucrose can be transformed into a jelly- like mass. The formed polysaccharide dextran collects around the cells as so-called mucus . If Leuconostoc species are cultivated on a solid nutrient medium containing sucrose, they form large, slimy colonies, while on a nutrient medium containing glucose they grow as small colonies without the formation of mucus.

Other metabolic pathways include the conversion of acetyl-CoA to acetoin and diacetyl , the latter being important as a flavor in the manufacture of lactic acid foods.

MRS medium is used to cultivate these bacteria, in liquid form (MRS broth) or with the addition of agar-agar as a solid nutrient medium. It is not a selective nutrient medium, but offers all lactic acid bacteria a suitable range of nutrients, as it contains glucose, meat extract , yeast extract , peptone and various minerals . The optimal temperature for incubation is around 30 ° C.

The representatives of the genus Leuconostoc can tolerate a high content of glucose without affecting their growth. Similar to the osmophilic yeast, they can reproduce in habitats with low water activity . In this context, bacteria are referred to as xerotolerant . Leuconostoc TYPES grow in a medium containing 30-40% glucose and are thus xelotolerant.

Occurrence

Milk is the natural habitat of numerous Leuconostoc species. Leuconostoc mesenteroides can be isolated from many plant surfaces, this being the case with intact, but also with decomposing parts of plants. The Leuconostoc species naturally present in white cabbage are often involved in the production of sauerkraut ; a strain isolated from sauerkraut was identified as a new species in 1992.

meaning

They play an important role in various fermentations . For example, the subspecies Leuconostoc mesenteroides subsp. cremoris is used in dairies as a starter culture for making butter and cheese . Other species are involved in the production of silage and sauerkraut, where lactic acid fermentation is also important. Many different microorganisms are involved in the fermentation of coffee beans . Studies from 2007 showed that Leuconostoc is also involved and led to the discovery of a new species. Leuconostoc species can also lead to food spoilage if lactic acid is not formed is desirable. In addition to the spoilage of fresh milk due to "souring", vacuum-packed meat and sausage products are also affected, as the bacteria can grow there under anaerobic conditions. The same applies to products packed in a protective gas atmosphere (such as carbon dioxide). In immunocompromised patients, Leuconostoc species can cause bacteremia and abscesses in the abdomen.

Systematics

External system

Leuconostoc resembles the representatives of the genus Lactococcus in terms of its cellular appearance . Both genera also have similarities in their DNA composition. The GC content (the proportion of the nucleobases guanine and cytosine ) in the bacterial DNA is 38-41 mol percent in each case. However, they differ in their metabolism, as Leuconostoc performs heterofermentative lactic acid fermentation, while for Lactococcus the homofermentative lactic acid fermentation is typical.

Internal system

Numerous species belong to the genus . T. are still divided into subspecies (subspecies). The systematics of bacteria changes regularly, as new research results make a different classification necessary or new species are discovered and described. The current status can be viewed in the List of Prokaryotic names with Standing in Nomenclature (LPSN). The Leibniz Institute DSMZ - German Collection of Microorganisms and Cell Cultures GmbH keeps a corresponding list.

Thereafter, (as 2013) include the following 13 species of the genus Leuconostoc :

Four types of bacteria that were previously assigned to the genus Leuconostoc have belonged to the new genus Fructobacillus since 2008 :

  • Fructobacillus durionis (Leisner et al. 2005) Endo and Okada 2008 (previously Leuconostoc durionis )
  • Fructobacillus ficulneus (Antunes et al. 2002) Endo and Okada 2008 (previously Leuconostoc ficulneum )
  • Fructobacillus fructosus (Kodama 1956) Endo and Okada 2008 (previously Leuconostoc fructosum )
  • Fructobacillus pseudoficulneus (Chambel et al. 2006) Endo and Okada 2008 (previously Leuconostoc pseudoficulneum )

In addition to genetic examinations, metabolic physiological characteristics also showed that the assignment to the genus Leuconostoc was inconclusive. The Fructobacillus TYPES not produce ethanol, but a typical product of metabolism is the heterofermentative lactic acid fermentation. Instead, glucose is broken down into lactic acid and acetic acid . In addition, the picture shows rod-shaped cells in the scanning electron microscope .

swell

literature

  • Michael T. Madigan, John M. Martinko, Jack Parker: Brock Microbiology. German translation edited by Werner Goebel. 1st edition. Spektrum Akademischer Verlag GmbH, Heidelberg / Berlin 2000, ISBN 3-8274-0566-1 .
  • A. Endo, S. Okada: Reclassification of the genus Leuconostoc and proposals of Fructobacillus fructosus gen. Nov., Comb. nov., Fructobacillus durionis comb. nov., Fructobacillus ficulneus comb. nov. and Fructobacillus pseudoficulneus comb. nov. In: International Journal of Systematic and Evolutionary Microbiology . tape 58 , no. 9 , 2008, p. 2195–2205 , doi : 10.1099 / ijs.0.65609-0 ( PDF, 300 kB [accessed on August 16, 2013]).

Individual evidence

  1. ↑ a b c d e Microorganisms in class . In: Horst Bayrhuber, Eckhard R. Lucius (ed.): Handbook of practical microbiology and biotechnology . 1st edition. tape 3 . Metzler-Schulbuchverlag, Hannover 1992, ISBN 3-8156-3351-6 , p. 60-62 .
  2. ↑ a b c d e f Hans G. Schlegel, Christiane Zaborosch: General microbiology . 7th edition. Thieme Verlag, Stuttgart / New York 1992, ISBN 3-13-444607-3 .
  3. ^ A b Jean Euzéby, Aidan C. Part: Genus Leuconostoc. (No longer available online.) In: List of Prokaryotic names with Standing in Nomenclature (LPSN) . Archived from the original on November 4, 2013 ; Retrieved August 15, 2013 . Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. @1@ 2Template: Webachiv / IABot / www.bacterio.net
  4. ↑ a b c d A. Endo, S. Okada: Reclassification of the genus Leuconostoc and proposals of Fructobacillus fructosus gen. Nov., Comb. nov., Fructobacillus durionis comb. nov., Fructobacillus ficulneus comb. nov. and Fructobacillus pseudoficulneus comb. nov. In: International Journal of Systematic and Evolutionary Microbiology. Volume 58, Number 9, September 2008, pp. 2195-2205, ISSN  1466-5026 . doi : 10.1099 / ijs.0.65609-0 . PMID 18768629 .
  5. ↑ a b c Michael T. Madigan, John M. Martinko, Jack Parker: Brock Mikrobiologie. German translation edited by Werner Goebel. 1st edition. Spektrum Akademischer Verlag GmbH, Heidelberg / Berlin 2000, ISBN 3-8274-0566-1 .
  6. ↑ Catalog of microorganisms. In: Website of the Leibniz Institute DSMZ - German Collection of Microorganisms and Cell Cultures GmbH . Retrieved August 16, 2013 .
  7. ↑ a b A.J. Martinez-Murcia, MD Collins: A phylogenetic analysis of an atypical leuconostoc: description of Leuconostoc fallax sp. nov. In: FEMS Microbiology Letters. Volume 82, Number 1, July 1991, pp. 55-59, doi : 10.1111 / j.1574-6968.1991.tb04839.x .
  8. ↑ a b K. De Bruyne, U. Schillinger u. a .: Leuconostoc holzapfelii sp. nov., isolated from Ethiopian coffee fermentation and assessment of sequence analysis of housekeeping genes for delineation of Leuconostoc species. In: International Journal of Systematic and Evolutionary Microbiology. Volume 57, Number 12, December 2007, pp. 2952-2959, doi : 10.1099 / ijs.0.65292-0 .
  9. ↑ a b c B. G. Shaw, CD Harding: Leuconostoc gelidum sp. nov. and Leuconostoc carnosum sp. nov. from Chill-Stored Meats. In: International Journal of Systematic Bacteriology. Volume 39, Number 3, July 1989, pp. 217-223, doi : 10.1099 / 00207713-39-3-217 .
  10. ^ Marianne Abele-Horn: Antimicrobial Therapy. Decision support for the treatment and prophylaxis of infectious diseases. With the collaboration of Werner Heinz, Hartwig Klinker, Johann Schurz and August Stich, 2nd, revised and expanded edition. Peter Wiehl, Marburg 2009, ISBN 978-3-927219-14-4 , p. 264.
  11. ^ Prokaryotic Nomenclature Up-to-date. In: Website of the Leibniz Institute DSMZ - German Collection of Microorganisms and Cell Cultures GmbH . Retrieved August 16, 2013 .

Web links