Gluconobacter oxydans

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A Microbial Biorealm page on the genus Gluconobacter oxydans

Classification

Higher order taxa

Domain: Bacteria; Phylum: Proteobacteria; Class: Alphaproteobacteria; Order: Rhodospirillales; Family: Acetobacteraceae; Genus: Gluconobacter; Species: oxydans [Others may be used. Use NCBI link to find]

Species

NCBI: Taxonomy

oxydans

Description and significance

© DECHEMA e.V. 2004, Last update 2006-03-08

Gluconobacter oxydans, previously known as Acetobacter suboxydans, are Gram-negative rod or oval shaped bacterium ranging from about 0.5 to 0.8mm x to 4.2mm. They tend to have a small genome size because of their limited metabolic abilities. These abilites include partially oxidizing carbohydrates and alcohols through the process of oxidative fermentation, and they can be used for sythesis of Vitamin C, D-gluconis acid and ketogluconic acids.[3] G. oxydans are found in flowers, fruits, garden soil, alcoholic beverages, cider, and soft drinks because they are capable of growing strains in high concentrations of sugar solutions and low pH values (optimal pH for growth is 5.5-6.0).[2] Although they are able to grow in extreme conditions, its growth rate is slow and the concentration of mature cells are low. The importance of G. oxydans is its ability to incompletely oxidize carbon substrates such as D-sorbitol, glycerol, D-fructose, and D-glucose for the use in biotechnological instruments.[3]

Genome structure

The genome of Gluconobacter oxydans tend to be small in size, ranging about 2240 to 3787kb (Verma et al., 1997). Shapes can be ellipsoidal or rod-shaped with dimensions of 0.5 to 0.8x0.9 to 4.2mm. The total number of genes is 2664, the total number of all DNA molecules is 6, and the total size of all the DNA molecules is 2922384bp. The circular chromosome has a size of 2.7Mb and a total of 2743 reading frames. It contains four plasmids with sizes of 26.6kb, 14.5kb, 13.2kb, and 2.7kb, and a megaplasmid with a size of 163kb. Its G+C content is 61%. G. oxydans is an aerobe which has oxygen as a terminal electron acceptor. The highest growth rate occur at temperatures between 25 to 30 degrees C and it cannot withstand high temperatures above 37 degrees C. G. oxydans are interesting because they cause apples and pears to rot and they thrive in environments with high concentrations of sugar.[3]

Cell structure and metabolism

Describe any interesting features and/or cell structures; how it gains energy; what important molecules

Gluconobacter oxydans has two membranes and no flagella and are thus non-motile. Since they are aerobes, they must oxidize to get their energy.[3] One method involves oxidation of sugars, aliphatic and cyclic alcohols, and steroids to oxidation product. Another method is through the pentose phosphate pathway where phosphorylation occurs initially then proceeds with oxidation through the pathway. It is suggested that G. oxydans has an incomplete set of tricarboxylic acid cycle (TCA)enzymes because the carbon dioxide produced from glucose was from the pentose phosphate pathway. They possess properties for TCA because they are primarily responsible for the biosynthesis of glutamate, aspartate, and succinate. The main function of G. oxydans is their oxidative capabilites. It uses membrane-bound dehydrogenases to oxidize polyols into ketones and sugars into acids.[3]

Ecology

Describe any interactions with other organisms (included eukaryotes), contributions to the environment, effect on environment, etc.

Gluconobacter oxydans is often found in sugar rich or alcoholic areas. It contributes to the environment by oxidizing sugars, sugar acids, and sugar alcohols. It can cause fruits to rot like rotten apples and pears. G. oxydans can incompletely oxidize substrates under natural conditions.[5]

Pathology

Gluconobacter oxydans strains are non-pathogenic to humans or animals, but they cause bacterial rot to apples and pears turning them shades of brown.[2]

Application to Biotechnology

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

Gluconobacter oxydans is useful for a number of biotechnological applications.

It goes through the process of oxidizing glycerol to dihydroxyacetone(DHA). The use of a membrane-bound glycerol dehydrogenase to oxidize sorbitol, gluconate, and arabitol.

Production of vitamin C, sorbitol, xylitol, and vinegar are aided with the addition of G. oxydans.

Biosensors using G. oxydans can be used to measure substrate concentration as a biosensor. Ehtanol in air, glycerol in fermentation media, and glucose in humans are just a few of the exciting applications currently being researched.

Current Research

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

References

Edited by Lynn S Cheung student of Rachel Larson and Kit Pogliano


[1]Prust, C., Hoffmeister, M., Liesegang, H., Wiezer, A., Fricke, W. F., Ehrenreich, A., Gottschalk, G. and Deppenmeier, U. (2005) Complete genome sequence of the acetic acid bacterium Gluconobacter oxydans. Nature Biotechnol. 23(2): 195-200 (abstract).

[2]Gupta A, Singh VK, Qazi GN, Kumar A. Gluconobacter oxydans:its biotechnological applications. J Mol Micrcobiol Biotechnol. 2001 Jul.

[3]Sue Macauley, Brian McNeil, and Linda M. Harvey. 'The Genus Gluconobacter and Its Applications in Biotechnology'. Critical Reviews in Biotechnology, 21:1, 1-25.

[4]http://cmr.tigr.org/tigr-scripts/CMR/GenomePage.cgi?org=ntgo01 'Gluconobacter oxydans 621H Genome page', Comprehensive Microbial Resource

[5]Cornelia Gatgens, Ursula Degner, Stephanie Bringer-Meyer, and Ute Herrmann. 'Biotransformation of glycerol to dihydroxyacetone by recombinant Gluconobacter oxydans DSM 2343'. Biotechnological Products and process engineering. April 2007.