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hello everyone my name is mariani i'm a

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phd student based in brazil

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and i'll be presenting some preliminary

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results of the uvc resistance

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in non-pigmented yeasts isolated from

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the atacama desert

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microorganisms have long been known for

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their importance not only for the

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ecological balance

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but also for biotechnology processes

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this is especially true for

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extremophiles which can withstand

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extreme environmental conditions such as

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heat or

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ph and those are very useful for

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biotechnological processes

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besides thermophiles and alkali files

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the radio-resistant microorganisms have

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also been studied

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not only because of the bioproducts that

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they offer with special application

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in the pharmaceutical industry but also

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because of the recent advent

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of techniques for synthetic biology in

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which

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broadly speaking their molecular

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mechanisms of resistance could be

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applied to improve

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non-resistant microorganisms

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radio-resistant microorganisms can also

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be applied for

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studies on astrobiology including the

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better understanding of how this could

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cope

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with the extreme parameters of

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extraterrestrial habitats but also on

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primitive earth

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ultraviolet radiation is primarily

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composed of three wavelength ranges

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uva uvb and uvc only the uva and uvb

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ranges can reach the earth's surface and

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although being essential for our life on

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earth

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this can still cause direct and indirect

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deleterious effects

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such as mutagenic lesions and increases

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in the levels of reactive oxygen species

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mars on the other hand is affected also

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by the ultraviolet

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wavelengths of the uvc range uvc

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is even more deleterious leading to

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higher rates of mutations compared to

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uva

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or uvb while you still cannot take these

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organisms to be studied in sido on mars

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the so-called analogous environments are

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still a very useful way

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of understanding how organisms can cope

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with such extreme conditions

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in that regard the atacama desert is an

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analogous environment with lots of

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similar conditions

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as what we would observe in mars surface

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the high incidence of ultraviolet

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radiation is one of these parameters

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and so the study of organisms coping

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with such extreme uv levels

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is a very good way of learning more

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about how life could survive

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on mars most of the radio resistant

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microorganisms

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retrieved from the soils of the atacama

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desert are pigmented bacteria

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with melanin and carotenoids as they

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primarily found pigments

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non-pigmented microorganisms on the

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other hand still lacking studies and are

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only currently being receiving

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the deserved attention this is

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especially true for non-pigmented

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eukaryotes such as

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its east isolates therefore this study

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aimed to provide the first understanding

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of the

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resistance to utter violent radiation of

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non-pigmented extremophilic yeast

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these were isolated from the soils of

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the atacama desert back in 2012

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and two of them were already

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characterized by potion and

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collaborators in 2015.

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so here we have a picture of two

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pigmented yeasts isolated during that

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campaign

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exophiala and brothers peridot as well

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as the two non-pigmented yeasts

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naganisha fridamani

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in their paper push and collaborators

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demonstrated with raymond

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spectrometry that neither melanine nor

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carotenoids could be identified

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in the two non-pigmented isolates later

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on the team could also

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isolate eight more of the non-pigmented

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yeasts from the same samples

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these are yet to be identified and were

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used for the uvc experiments in this

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study

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so the non-pigmented yeasts were

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cultivated in yeast media for

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48 hours at 25 degrees celsius

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and then replicated to solid media for

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the uvc exposure

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48 hours after the exposure the colony

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farming units were counted and compared

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to non-exposed

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control colon because we don't have a

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radiometer in our lab we use the growth

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of the previously characterized

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naganisha predomini

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as a pattern to estimate the uvc fluency

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being used

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so as you can see in these graphs

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naganisha's growth is reduced in one log

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order after 30 seconds of exposure

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which falls well into the 0.6 kilojoules

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per square meter

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observed on pushon's experiment likewise

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after 60 seconds of exposure

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naganisha's growth is reduced to

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one-third of the original growth

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endorsing the estimates of a double

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fluency of 1.2

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kilojoules per square meter

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thus we can conclude that naganisha's

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survival cfu numbers can be used as a

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reliable pattern

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for estimating the uvc fluids for our

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our experiments

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then we exposed all us isolates

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intruplicates to the same uvc

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fluences of 0.6 and 1.2 kilojoules

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per squared meter and we can see from

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this graph that most of the isolates

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present

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a singular resistant pattern to what's

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observed

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with naganesha some of the yeasts even

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presented a potentially higher

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resistance compared to naganisha

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frederimani

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this is especially true for the 13b

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isolate with a reduction

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of only one log fold even after exposure

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to the highest uvc dose

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in conclusion we can state that the

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growth pattern observed for naganisha

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fregimony after uvc exposure

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can be used as an estimate for total uvc

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fluency

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east isolate 13b presented the highest

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uvc resistance and provides a powerful

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potential for further studies

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all other es isolates presented overall

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resistance to uvc

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and endorse the potential of desert

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non-pigmented yeasts as radio-resistant

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organisms

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these isolates shall be further explored

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for the potential

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sources of bioproducts with importance

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for biotechnology

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as well as for their potential as role