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Suicidal bacteria: Unicellular organisms occasionally poison themselves with a toxin

Date:
March 15, 2013
Source:
Albert-Ludwigs-Universität Freiburg
Summary:
The cyanobacterium Synechocystis produces toxins that often lead to its own demise. Biologists have now determined the logic governing this mechanism..

A typical liquid culture of the cyanobacterium Synechocystis.
Credit: Stefan Kopfmann

The cyanobacterium Synechocystis produces toxins that often lead to its own demise. The biologists Stefan Kopfmann and Prof. Dr. Wolfgang Hess from the University of Freiburg have determined the logic governing this mechanism.

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Their findings have been published in the Journal of Biological Chemistry (JBC) and PLoS ONE.

The cyanobacterium Synechocystis produces several toxins. However, most of the time they cannot become active because the unicellular organism usually only produces them together with an antitoxin that neutralizes their poisonous effect. This is a trick of nature: The genes for the toxin and the antitoxin are located together on a plasmid, i.e. a fragment of DNA that exists independently of the actual bacterial chromosome. In contrast to the toxin, the antitoxin is not very stable. When a cell loses the plasmid during cell division, both of the genes are lost. Since the toxin is more stable than the antitoxin and is thus effective for a longer period of time, these cells eventually die off. Hence, the toxin-antitoxin pairs constitute a natural selection mechanism that sees to it that only cells which retain the plasmid survive.

The plasmid pSYSA of the cyanobacterium Synechocystis has not one but seven different systems of this kind and is thus well protected. The reason for this is because in addition to the genes for the seven toxin-antitoxin pairs, the plasmid pSYSA possesses the genetic information for a bacterial immune system. If the plasmid with this system gets lost in cell division, several toxins thus see to it that the bacterium is killed. The fact that the genes responsible for it are combined with a high amount of toxin-antitoxin pairs indicates that this system has special significance for the cyanobacterial cell.

The project is supported by funding from the German Research Foundation.


Story Source:

The above story is based on materials provided by Albert-Ludwigs-Universität Freiburg. Note: Materials may be edited for content and length.


Journal References:

  1. S. Kopfmann, W. R. Hess. Toxin-Antitoxin Systems on the Large Defense Plasmid pSYSA of Synechocystis sp. PCC 6803. Journal of Biological Chemistry, 2013; 288 (10): 7399 DOI: 10.1074/jbc.M112.434100
  2. Ingeborg Scholz, Sita J. Lange, Stephanie Hein, Wolfgang R. Hess, Rolf Backofen. CRISPR-Cas Systems in the Cyanobacterium Synechocystis sp. PCC6803 Exhibit Distinct Processing Pathways Involving at Least Two Cas6 and a Cmr2 Protein. PLoS ONE, 2013; 8 (2): e56470 DOI: 10.1371/journal.pone.0056470

Cite This Page:

Albert-Ludwigs-Universität Freiburg. "Suicidal bacteria: Unicellular organisms occasionally poison themselves with a toxin." ScienceDaily. ScienceDaily, 15 March 2013. <www.sciencedaily.com/releases/2013/03/130315074607.htm>.
Albert-Ludwigs-Universität Freiburg. (2013, March 15). Suicidal bacteria: Unicellular organisms occasionally poison themselves with a toxin. ScienceDaily. Retrieved November 29, 2014 from www.sciencedaily.com/releases/2013/03/130315074607.htm
Albert-Ludwigs-Universität Freiburg. "Suicidal bacteria: Unicellular organisms occasionally poison themselves with a toxin." ScienceDaily. www.sciencedaily.com/releases/2013/03/130315074607.htm (accessed November 29, 2014).

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