Extremophiles

Summery: This was a test of Mn (manganese) in Deinococcus Radiodurans, testing it's effect, etc. Two test groups were conducted one of Mn (manganese) and two days of waiting (group A) and one of MnSO- (manganese solphate) and waiting of 6 days (group B). These tests were enacted on 14 hour old D. Radiodurans. Group B did not form toroids and became radio-sensitive. It is assumed that toroids are part of the reason for D. Radiodurans radio-resistance. Group A failed to form compartments or membrane orifices (which can be problematic for a bacterium).

"Transmission electron micrographs of MnSO4-treated D. radiodurans. MnSO4(100 μM) was added to the growth medium at the late logarithmic phase (14 hours old), and the cells were incubated for an additional (A) 48 hours or (B) 6 days. Bacteria exposed to Mn2+ formed aggregates but were noncompartmentalized and had no detectable membrane orifices. (C to E) Different morphologies exhibited by DNA-stained cells (10) exposed to MnSO4 for 6 days, showing that in these cells, genomes, which are darkly stained, do not form toroids. BecauseD. radiodurans cells exposed to large extracellular concentrations of Mn2+ become radiation sensitive (21), the absence of DNA toroids indicates that toroidal packaging is correlated with radioresistance. Scale bars, 500 nm." Science 10 January 2003: Vol. 299 no. 5604 pp. 254-256 DOI: 10.1126/science.1077865

Smadar Levin-Zaidman1,

Joseph Englander1,

Eyal Shimoni1,

Ajay K. Sharma2,

Kenneth W. Minton3,

This is a model of ionizing radiation driven manganese and iron redox cycling. There are several hypotheses on how Deinococcus Radiodurans is able to repair it's DNA after it is exposed to radiation. One of those hypotheses involves the use of manganese.

"Under ionizing radiation (IR), Fe2+ and Fe3+ redox cycling is predicted to generate HO and O2-, whereas Mn2+ and Mn3+ redox cycling is predicted to favour O2- scavenging without HO production. Catalase is a common enzyme that catalyses the decomposition of H2O2 to O2 and H2O. Thus, under anaerobic or aerobic irradiation conditions, in a cascade of events, O2- would damage and inactivate enzymes with exposed Fe–S clusters, thereby triggering the release of Fe2+, and 'free' Fe2+ would promote IR-driven Fe2+ and Fe3+ redox cycling. Fe–S clusters participate in a range of biochemical processes, including electron transfer, substrate binding and activation, redox catalysis, DNA replication and repair, regulation of gene expression, and tRNA modification. Thus, Mn2+ and Mn3+ redox cycling is predicted to prevent the proliferation of iron-dependent reactive oxygen species and protect diverse cellular functions."

Images of Deinococcus Radiodurans.

1) http://biologypop.com/wp-content/uploads/2013/07/Deinococcus-radiodurans5.jpg

2) http://vonneumannmachine.files.wordpress.com/2009/04/d_radiodurans.jpg

3) http://bioweb.uwlax.edu/bio203/s2008/arnold_meag/unnamed/More%20Images/Michael%20Daly.jpg

4) http://bioweb.uwlax.edu/bio203/s2008/arnold_meag/Images/Dennis%20Kunkel%20B.jpg

"The genome structure of Deinococcus radiodurans is made up of two chromosomes (2,648,638 and 412,348 base pairs), a megaplasmid (177,466 base pairs), and a small plasmid (45,704 base pairs), creating a genome of 3,284,156 base pairs (TIGR, 2004)."

Deinoccocus Radiodurans = Deino Radio

Deinococcus Radiodurans was discovered in 1956 at the Oregon Agricultural Experiment Station in Corvallis by Arthur W. Anderson. An experiment was being conducted to investigate whether meat could be sterilized when treated with gamma radiation. The meat later spoiled despite the radiation treatment do to Deinococcus Radiodurans in the meat. Arthur isolated the bacteria in the can of spoiled meat.

Deinococcus Radioduran is one of the most extreme extremophiles out there. It is able to survive 5000-30,000 Gy. For perspective, humans will die when exposed to 5 Gy. (Gray; one Gray = 100 rad).

http://www.life.umd.edu/labs/delwiche/bsci348s/lec/Deinococcus.html