Clostridium acetobutylicum: Difference between revisions

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Gimenez, J.A. and H. Sugiyama. 1988. [http://iai.asm.org/cgi/content/abstract/56/4/926 Comparison of toxins of Clostridium butyricum and Clostridium botulinum type E.] Infection and Immunity 56:926-929.
Gimenez, J.A. and H. Sugiyama. 1988. [http://iai.asm.org/cgi/content/abstract/56/4/926 Comparison of toxins of Clostridium butyricum and Clostridium botulinum type E.] Infection and Immunity 56:926-929.


Gutierrez, Noemi A., Maddox, Ian S. http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?CMD=Display&DB=pubmed Role of Chemotaxis in Solvent Production by Clostridium acetobutylicum] Appl. Environ. Microbiol. 1987 53: 1924-1927
Gutierrez, Noemi A., Maddox, Ian S. [http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?CMD=Display&DB=pubmed Role of Chemotaxis in Solvent Production by Clostridium acetobutylicum] Appl. Environ. Microbiol. 1987 53: 1924-1927


Chen, J.S., Toth, J., and Kasap, M. (2001) [http://www.springerlink.com/content/7ny38wuyh03ra50t/?p=5deea648464341c6a78053aef66a8bec&pi=7 Nitrogen-fixation genes and nitrogenase activity in Clostridium acetobutylicum and Clostridium beijerinckii.] J Ind Microbiol Biotechnol 27: 281–286.
Chen, J.S., Toth, J., and Kasap, M. (2001) [http://www.springerlink.com/content/7ny38wuyh03ra50t/?p=5deea648464341c6a78053aef66a8bec&pi=7 Nitrogen-fixation genes and nitrogenase activity in Clostridium acetobutylicum and Clostridium beijerinckii.] J Ind Microbiol Biotechnol 27: 281–286.

Revision as of 01:29, 5 June 2007

A Microbial Biorealm page on the genus Clostridium acetobutylicum

Image of Clostridium acetobutylicum courtesy of NCBI.

Classification

Higher order taxa

Bacteria (Domain); Firmicutes (Phylum); Clostridia (Class); Clostridiales (Order); Clostridiaceae (Family); Clostridium (Genus)

Species

Clostridium acetobutylicum

Clostridium acetobutylicum ATCC 824 is considered the type strain.

NCBI: Taxonomy

Description and significance

Clostridium acetobutylicum is a Gram-positive bacillus. C. acetobutylicum is most often soil dwelling, although it has been found in a number of different environments. It is mesophilic with optimal temperatures of 10-65°C. In addition, the organism is saccharolytic (can break down sugar) and capable of producing a number of different commercially useful products; most notably acetone, ethanol and butanol.[1]

C. acetobutylicum requires anaerobic conditions in order to grow in its vegetative state. In its vegetative states, it is motile via flagella across is entire surface. It can only survive up to several hours in aerobic conditions, in which it will form endospores that can last for years even in aerobic conditions. Only when these spores are in favorable anaerobic conditions will vegetative growth continue.

It was first isolated between 1912 and 1914. Chaim Weizmann cultured the bacteria to be used to produce acetone, ethanol and butanol (ABE method) which was used to produce TNT and gunpowder in the first World War. Following WWI, the ABE process was widely used until the 1950's when petrochemical processes were more cost-effective due to the cost and availability of petroleum fuel sources. The recent fossil fuel crisis has spurred more research into C. acetobutylicum and the utilization of the ABE process.

Genome structure

The genome of Clostridium acetobutylicum ATCC 824 has been sequenced. This is the model strain for solvent-producing bacteria. It consists of one circular chromosome and a plasmid. The chromosome contains 3,940,880 base pairs. There are 11 operons coding for ribosomes, each of which is near the oriC and oriented in the direction of the leading strand of the replication fork. This is a characteristic commonly observed known as gene dosage, in which highly transcribed genes are placed near the oriC. There is little strand bias with approximately 51.5% of genes being transcribed from forward strand and 49.5% from the complementary strand.

In addition, the genome consists of one megaplasmid involved with solvent production and aptly named pSOL1. pSOL1 contains 192,000 base pairs and codes for 178 polypeptides. Examination of the plasmid indicates no obvious bias in the coding strand. pSOL1 contains four genes which are vital for alcohol and acetone production and the loss of this plasmid contributes to degeneration of the strain after many vegetative transfers or being maintained in a continuous culture. Further, mutants lacking these genes and unable to produce solvent resume acetone and alcohol production upon complementation of the genes via plasmids.

Examination of other strains of the organism such as ATCC 4259 have demonstrated that solvent producing genes again exist on the plasmid, named pWEIZ. Degeneration of the strain due to serial culturing is likely due to loss of this plasmid. Interestingly, these degenerate strains also do not sporulate spurring the idea that genes involved in sporulation also exist on the plasmid.

Cell structure and metabolism

Energy metabolism and byproducts

Considerable research has been invested into metabolic pathways of Clostridium acetobutylicum in order to improve industrial fermentation operations.

The metabolic pathways which produce solvents are those most notable in C. acetobutylicum. Acetone, acetate, butanol, butyrate, and ethanol are all made from acetyl-CoA.

Mutants which do not produce acetone or alcohol, such as mutant M5 of strain C. acetobutylicum ATCC 824 have been shown to lack of three enzymes in vitro: butyraldehyde dehydrogenase (BYDH), acetoacetate decarboxylase(AADC), and acetoacetyl-coenzyme A:acetate/butyrate:coenzyme A-transferase (CoAT). These enzymes are coded for on the plasmid within the sol operon by the following genes: AADC (adc), CoAT (ctfA, ctfB) and BYDH (aad).

In addition, C. acetobutylicum codes for many proteins that aid in the breakdown of xylan, levan, pectin, starch, and other polysaccharides. Interestingly, while the presence of genes which commonly code for cellusomes, protein complexes which breakdown crystalline cellulose, has been detected, the organism is unable to grow solely on cellulose substrates.

The organism is also capable of fixing atmospheric nitrogen after determination using labeled Nitrogen isotope. Another bacterium in the Clostridium family, Clostridium pasteurianum was first identified as being capable of nitrogen fixation and the genes involved in the process were sequenced. After sequencing, C. acetobutylicum ATCC 824, a series of genes very similar to the nitrogen fixing genes in C. pasteurianum were found, further confirming the bacterium's ability to utilize atmospheric nitrogen.

Cell Structure and Development

Cell structure and development is characterized by the development of an endospore when exposed to unfavorable conditions. Anaerobic conditions, formation of organic byproducts, and dissipation of the proton gradient outside the cytoplasmic membrane all lead to sporulation. This is in contrast to the other model organism of endospore formation, Bacillus subtilis, which forms endospores due to limitation of nutrients.

C. acetobutylicum has peritrichous flagella (flagella which cover the entire surface of the cell). Increased motility of the bacteria have been implicated in increased solvent production due to chemotaxis. Attractants include butyric acid and sugar. Notable repellents include acetone, butanol, and ethanol. This mechanism is logical in allowing the cell to find nutrients and move away from byproducts produced by its own metabolism.

Ecology

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

Pathology

C. acetobutylicum is completely benign to both plants and animals, however, many other species in the Clostridium genus are known pathogens, including: Clostridium difficile, Clostridium botulinum, Clostridium tetani, and Clostridium perfringen. In particular, C. botulinum and C. tetani, produce some of the most deadly neurotoxins known.

C. acetobutylicum has been found in the human colon, however, it is not known to be a part of normal human flora. In addition, because the organism does not appear to be toxic to mammals through the production of intracellular or extracellular substances, the organism would have to be present in enormous quantities to produces any threat.

The only issue of pathology with C. acetobutylicum is acquiring genes from pathogenic Clostridium such as C. tetani or C. botulinum. While there are no reported cases of C. acetobutylicum acquiring these genes, there have been incidents in the literature in which other Clostridium species have caused infant botulism with toxins very similar to those present in C. botulinum. The similarity of the toxins suggest that the normally non-toxigenic Clostridium strain acquired toxin-coding genes from C. botulinum, which are likely present on a plasmid.


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

C. acetobutylicum has been the focus of research as a specific mechanism of delivery of therapeutic drugs to cancerous regions of the body. C. acetobutylicum is necessarily anaerobic and therefore intravenous injection of spores will result in germination only in hypoxic regions of solid tumors in the body. Genetic manipulation of C. acetobutylicum in order to produce enzymes which will activate pro drugs within the tumorous region provides an extremely specific delivery mechanism to these tumor sites.

Hydrogen gas production via C. acetobutylicum as an alternative energy source.

Butanol fermentation via new patented process in replacement to ABE process.

References

Taxonomy:NCBI

[1] Nolling J et al., "Genome sequence and comparative analysis of the solvent-producing bacterium Clostridium acetobutylicum.", J Bacteriol, 2001 Aug;183(16):4823-38.

Keis, S., Shaheen, R., and Jones, D.T. "Emended descriptions of Clostridium acetobutylicum and Clostridium beijerinckii, and descriptions of Clostridium saccharoperbutylacetonicum sp. nov. and Clostridium saccharobutylicum sp. nov." Int. J. Syst. Evol. Microbiol. (2001) 51:2095-2103.

Cornillot E, Soucaille P. Solvent forming genes in Clostridia. Nature. 1996;380:489.

Fabrice Sabathe, Anne Belaıch, Philippe Soucaille (2002) Characterization of the cellulolytic complex (cellulosome) of Clostridium acetobutylicum FEMS Microbiology Letters 217 (1), 15–22.

P. Durre and C. Hollergschwandner, Initiation of endospore formation in Clostridium acetobutylicum, Anaerobe 10 (2004), pp. 69–74.

Jones, D. T., and D. R. Woods. 1986. Acetone-butanol fermentation revisited. Microbiol. Rev. 50:484-524.

Gimenez, J.A. and H. Sugiyama. 1988. Comparison of toxins of Clostridium butyricum and Clostridium botulinum type E. Infection and Immunity 56:926-929.

Gutierrez, Noemi A., Maddox, Ian S. Role of Chemotaxis in Solvent Production by Clostridium acetobutylicum Appl. Environ. Microbiol. 1987 53: 1924-1927

Chen, J.S., Toth, J., and Kasap, M. (2001) Nitrogen-fixation genes and nitrogenase activity in Clostridium acetobutylicum and Clostridium beijerinckii. J Ind Microbiol Biotechnol 27: 281–286.

Nuyts S, Van Mellaert L, Theys J, Landuyt W, Lambin P, and Anne J. Clostridium spores for tumor-specific drug delivery. Anticancer Drugs. 2002 Feb;13(2):115-25.


Edited by Mark Hower, student of Rachel Larsen and Kit Pogliano