Can Adaptive Response and Evolution Make Survival of Extremophile Bacteria Possible on Mars?

The humidity on the surface of the red planet, Mars, drops steeply during the daytime as the temperature rises. In this situation, Martian microorganisms should have the capability to cope with desiccation. Extremophiles are microorganisms that are capable of surviving in extreme environmental conditions. It has previously been shown that a pre-exposure to low levels of either ionizing or non-ionizing radiation can induce resistance against subsequent exposure to high levels of different stressors (e.g. high doses of ionizing radiation) in a wide variety of living systems. Moreover, it has been shown that E. coli bacteria repeatedly exposed to a dose needed for 1% survival, and increasing the dose each time due to increased radioresistance for the same survival (1%), generates extremely radioresistant bacteria through directed evolution. Mortazavi et al. have warned that in a similar manner with extremophiles such as Deinococcus radiodurans, it would be very likely that this type of human-directed radioresistance makes E. coli bacteria resistant to all physical and chemical agents (generation of serious life-threatening micro-organisms). There are reports about the possibility of the existence of microbes in the salty puddles of Mars. On Mars, with its thin atmosphere and lack of the protective magnetic field, higher levels of space radiation cause more genetic mutations. Interestingly, these mutations in bacteria, which can make them resistant against radiation, can also make them resistant against desiccation. Moreover, the adaptive response to radiation in bacteria might play an important role in this process. As stated in a NASA report, the cells in the astronauts will be traversed by multiple protons before exposure to HZE particles. This sequential exposure might significantly increase the resistance against radiation. The same exposure in bacteria might not only induce resistance against the high levels of damage caused by HZEs, but also to other life-threatening factors for bacteria such as desiccation. In this paper, the current understanding of extremophiles and their capability of surviving in extreme environmental conditions as well as current findings about radioadaptive responses in bacteria will be discussed

Does Exposure of Astronauts\u27 Brains to High-LET Radiation in Deep Space Threaten the Success of the Mission?

Astronauts\u27 exposure to radiation is different from exposure to radiation on Earth. Besides cancer, cardiovascular disease and acute radiation syndrome, there are concerns over the potential behavioral and cognitive impairments caused by exposure of the astronauts\u27 central nervous system to high levels of space radiation. Therefore, potential behavioral and cognitive i mpairments caused by astronauts\u27 brains exposure to high levels of space radiation and the possibility of developing dementia and other motor neuron diseases are getting more attention. As NASA is interested in studies on radium deposition in human brain, and exposure of the brain to high linear energy transfer (LET) alpha particles, we have assessed the cognitive effects of long-term exposure of human brain to alpha particles which partly mimics astronauts\u27 exposure to high charge and energy (HZE) particles during upcoming mars missions. Dr. John Boice, President of NCRP, and his colleagues\u27 have stated that human brain exposed for years to alpha particles on Earth may be more relevant to a Mars mission in contrast with the mouse brain exposed to heavy ions for a few minutes. Interestingly, both Boice and NASA did not pay enough attention to this fact that radium as well as many other alpha emitters tend to accumulate in the bone, and the alpha particles whose energies are typically -5 MeV have a very short range (maximum lOs of um), so the radiation dose due to the alpha emitters would be localized to volumes near the cranium rather than being uniformly distributed throughout the cerebral and cerebellar parenchyma. Extraordinary high levels of Ra-226 have previously been reported in high background radiation areas of Ramsar, where people are consuming locally grown foods. In this paper, we will present data which provide a human brain radiation exposure analogue for upcoming Mars missions. Normally the dose to the functional parts of the brain are not likely to be significant, even with higher uptakes of the radium or other alpha-emitting isotopes in the cranium. Therefore, only residents with calcium-rich diet were selected for the study. Measurements of background gamma radiation was performed in their bedrooms, dining rooms, vegetable yards and gardens with citrus fruit trees of the dwellings in areas with high levels of Ra-226 in the soil and at a nearby control area with the same socio-economic factors. Moreover, the food frequency, reaction time, working memory and computational abilities as well as the Radium Ingestion Index (RII) of 47 participants (22 males and 24 females) from the hot areas, where the annual radiation absorbed dose from background radiation is up to 260 mSv/y, were studied, and the same things were studied for 17 participants (4 males and 13 females) from a nearby normal background radiation area with the same socioeconomic factors as at the hot areas. Our study showed that exposure of human brain to high LET particles did not affect the working memory. However, individuals with higher levels of radium ingestion had significantly increased reaction times. The increased reaction time in individuals with higher exposure levels to alpha particles emitted from ingested Ra-226 is an important finding, since similar conditions might occur in deep space, when astronauts\u27 brain cells are exposed to HZE particles. As the astronauts face numerous challenges in isolated and confined space environment, they should be able to respond quickly to different hazards. However, further studies are needed to verify if the fmdings in high radiation dose areas in Ramsar are relevant for deep space mission

The effects of microwave radiation on rabbit's retina

Purpose: Mobile cell phones are used extensively these days, and their microwave (MW) radiation has been shown to affect the eye. The purpose of the present study was to evaluate the effects of MW radiation on rabbit retina. Methods: This experimental study (concluded in 2015) was conducted on 40 adult white New Zealand rabbits. A Global System for Mobile Communications (GSM) cell phone simulator was used for MW irradiation. The rabbits were randomized into five groups (8 in each) and treated as follows: Group 1: no irradiation (sham); Group 2: irradiation at 10 cm for 1 day; Group 3: irradiation at 30 cm for 1 day; Group 4: irradiation at 10 cm for 3 days; and Group 5: irradiation at 30 cm for 3 days. Scotopic and photopic electroretinography (ERG) responses were obtained at baseline and 7 days after the last exposure. Then all the rabbits were euthanized, and their eyes were enucleated and sent for pathology examination. Kruskal–Wallis and Chi-Square tests were used to evaluate intergroup differences in ERG parameters and histological findings, respectively. Results: ERG responses obtained 7 days after irradiation did not show any statistically significant difference between the groups (P > 0.1, for all tested parameters). There were statistically non-significant trends toward greater changes in the MW irradiated eyes. In pathological examination, retina was normal with no sign of degeneration or infiltration. Ciliary body congestion was observed in greater fraction of those who received higher MW doses. (P = 0.005). Conclusions: Histopathologically, cell phone simulated MW irradiation had no significant detrimental effect on the retina. However, ciliary body congestion was observed in greater fraction of those who received higher MW doses. Although there was no significant difference between post-treatment mean ERG values, there were statistically non-significant trends toward greater changes in the MW irradiated eyes