Microorganisms and Radiation Mandy Ruegsegger
Outline • Current issue of topic • Radiation types • Role of microorganisms in soil • Damage caused in microbes by radiation • Evolved mechanisms for resistance
Questions to be Answered • What types of radiation exist? • How do microorganisms protect themselves from the harmful effects of radiation?
Types of Radiation(Ionizing) • Alpha radiation • Beta radiation • Gamma radiation • X radiation • Neutron radiation
Types of Radiation (Non-ionizing) • Neutron radiation • Electromagnetic radiation • Visible light • Infrared • Microwaves • Radio waves • Ultraviolet
2011 earthquake devastates northeastern Japan • March 11th an earthquake of magnitude 8.9 hit northeastern Japan • Tsunami caused by the earthquake overwhelmed protective walls and damaged reactors • Radiation was released into the environment
Role of Microorganisms in Soil • Nutrient Cycling • Creation of new soil • Participation of molecular communication throughout soils • Carbon dioxide by-product • Dictated levels of iron and phosphorus
Cryptococcus neoformans and Histoplasma capsulatum • Fungal species found in soil • Exist in melanized forms and non-melanized forms Melanized form has been found in areas associated with high levels of radiation
C. neoformans and H. capsulatum (continued) One study explored the effects of lethal and sub-lethal dosages of radiation to both the melanized and non-melanized C. neoformans and H. capsulatum • effects were measured by high-performance liquid chromatography, electron spin resonance, transmission electron microscopy, and autoradiography • Results showed that pigment produced by melanin protected the fungi from damage by radiation
Halobacterium salinarum • Archaeon species found in soil • Inhabit highly saline environments • Recognized by characteristic red color originating from bacterioruberins
H. salinarum (continued) An experiment of this organism consisted of placing it in solutions of potassium chloride and potassium bromide, followed by exposure to several dosages of radiation, and finally running remaining DNA through agarose gel electrophoresis. • Protection is provided by microorganisms containing intracellular halides • Potassium bromide served as better protector • Increased molarity in solutions produced no significant changes
Deinococcus radiodurans • Bacterium capable of growing under rates of radiation as high as 60Gy/hr • Discovered in 1967 • Most radiation-resistant microorganism known thus far • Contains 5 layers of outer membrane following plasma membrane
D. radiodurans (continued) • Possess the ability to repair DNA breaks
D. radiodurans (continued) • Genomic structure • Also believed that accumulation of manganese(II) plays part in resistance of radiation • Morphology takes on ringlike structure • Way upon which phenomenon occurs not yet established
Conclusion • Radiation exposure is potentially lethal • Microorganisms prove to be resilient to effects of radiation to a degree
References • 1. Blasius, M., et. al. (2008) Deinococcus radiodurans: What Belongs to the Survival Kit? Critical Reviews in Biochemistry and Molecular Biology 43: 221-238. • 2. Dadachova, E., et. al. (2007) The Radioprotective Properties of Fungal Melanin are a Function of its Chemical Composition, Stable Radical Presence and Spatial Arrangement. Pigment Cell and Melanoma Research 21: 192-199. • 3. Daly, M. J., et. al. (2004) Accumulation of Mn(II) in Deinococcus radiodurans Facilitates Gamma-Radiation Resistance. Science. • 4. Gadd, G. M., et. al. (2010) Geomicrobiology of Eukaryotic Microorganisms. Geomicrobiology journal 27: 491-519. • 5. Hue, N. V. (2009) Iron and Phosphorus Fertilizations and the Development of Proteoid Roots in Macadamia (Macadamia integrifolia). Plant Soil 318: 93-100. • 6. Kish, A., et. al. (2009) Salt Shield: Intracellular Salts Provide Cellular Protection Against Ionizing Radiation in the Halophilic Archaeon, Halobacterium salinarum NRC-1. Environmental Microbiology 11: 1066-1078. • 7. Lambers, H., et. al. (2009) Plant-Microbe-Interaction in the Rhizosphere: an Evolutionary Perspective. Plant and Soil 321: 83-115. • 8. Levin-Zaidman, S., et. al. (2003) Ringlike Structure of Deinococcus radiodurans Genome: A Key to Radioresistance? Science 299: 254-256. • 9. Makarova, Kira S., et. al. (2001) Genome of the Extremely Radiation-Resistant Bacterium Deinococcus radiodurans Viewed from the Perspective of Comparative Genomics. Microbiology and Molecular Biology Reviews 65: 44-79. • 10. Osborne, A., and Newell, A. “Deinococcus Radiodurans” (2009) http://www.andyannie.pbworks.com/w/page/4885308/structure. • 11. Schiave, L. A., et. al. (2009) Variability in UVB Tolerances of Melanized and Nonmelanized Cell of Cryptococcus neoformans and C. laurentii. Photochemistry and Photobiology 85: 205-213.