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hi everyone so I'll be talking about

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Martian metabolism and biotic chlorate

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reduction in Mars analog environments on

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Earth

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so uh since the discovery of let's see

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if I can get this video since the

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discovery of perchlorate

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on Mars by the Phoenix Lander in 2008

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it's been a compound of interest on the

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red planet this is due to its high

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oxidative potential on par with oxygen

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which means that it's a potential energy

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source for life on the red planet uh on

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Mars it's ubiquitous in Martian regolith

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reaching concentrations of 0.5 weight

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percentage

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um on Earth there are microbes that

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reduce perchlorate in place of oxygen

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and Metabolism using it to drive the

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electron transport chain

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and perchlorate accumulates in Mars

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analog systems on Earth such as the

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Atacama Desert where it reaches

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concentrations up to 0.18 percent

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as well as the Antarctic dry valleys

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where it reaches concentrations up to

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.0038 these are Mars analog systems that

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are incredibly dry and accumulate

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perchlorate via atmospheric deposition

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um over long time scales and uh

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they're likely uh looking at these

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systems it seems reasonable that per

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reducing microbes might evolve and

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persist in these types of environments

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however the model organisms that we use

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to study biotic perchlorate reduction

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don't come from Mars analog environments

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they come from the Potomac River in

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Washington DC where there's very little

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to no natural perchlorate that

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accumulates all the pcori that we do

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find here is um is waste from Munitions

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factories that gets dumped into the

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river so how did perchlorate reducing

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microbes arrive in this type of

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environment

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if they likely didn't evolve here due to

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the lack of perchloride well we know

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that the perchlorate reduction genomic

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island is widely spread via horizontal

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Gene transfer we know this because when

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we look at reducing organisms can you

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see my mouse yeah there we go

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um the elements required for biotic

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report reduction the genes that are

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required for court reduction

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um share a lot of homology between the

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genes but where the genes are situated

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in the genome is very diverse depending

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on the organism that you're looking at

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so it's a very chimeric metabolism so if

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we look here the the bright green that's

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chloride dismutates and this long dark

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green this perchlorate reductase they're

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always kind of in different

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configurations in relation to each other

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in uh in the genomic Island and that's

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because these individual elements are

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getting passed uh individually and um

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independently of one another via

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horizontal Gene transfer so you only get

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reducing microbes when these elements

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come together in the same organism

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so my research question was did

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canonical biotic reduction arise in

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these Mars analog environments like the

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atticama desert or Antarctic dry valleys

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and then disperse around the world via

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acellular and microbial dispersal

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so in order to test that I selected

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metagenoms from sites around the world

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the metagenome for those of you don't

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know is basically all the DNA in a

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sample it comes in little

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20 base pair of chunks and you have to

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piece them together like a puzzle and

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then pick out the puzzles that you're

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interested in uh that maybe make a

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picture you're interested in and then uh

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and then analyze those independent of

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the rest of the metagenome so basically

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what I did is I selected metagenoms from

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sites around the world I analyzed the

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presence of reduction genes so basically

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build the little puzzles and then pulled

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out the the ones that made reducing

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genes and then I calculated the

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phylogenetic diversity of those genes at

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each site this is a study that has

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really up until this point been done

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only in humans which is this uh type of

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analysis where we look at diversity of a

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species or a gene to determine the

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likely places where it's persisted the

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longest that's how we know that humans

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come out of Africa is because most of

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our phylogenetic diversity can be

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accounted for in Africa

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so when I did this uh so this is for

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chloride dismutase a gene that's

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involved in per quart reduction I found

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the highest diversity to be in uh in the

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uh Antarctic dry Valley so what we're

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seeing here is these bars are are a

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scale that's Faith's phylogenetic

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diversity zero is basically zero

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diversity and then up to 50 would would

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be the maximum amount of diversity in

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these genes that we see and each of

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these blue dots is a separate metagenome

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um as you can see there's a little bit

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of sampling bias because in the anterior

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dry valleys or Atacama Desert we have a

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lot more sampling there's a lot more

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research that happens in these sites

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we've got a lot more metagenomes that I

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can analyze whereas if I look at other

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Mars analog sites like the Namib Desert

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there are quite a few less or in South

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Australian desert uh much less access to

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that kind of data

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when I looked at procore reductase

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another Gene involved in biotic

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proportion reduction we also see that it

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is it reaches highest levels in the

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Antarctic dry valleys so that basically

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indicates that these genes have

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persisted the longest in in these in

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this in these in these Mars analog

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ecosystems supporting the claim that

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these may have evolved and persisted in

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those Mars analog systems

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so some conclusions uh reduction genes

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are present and diverse in Mars analog

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systems that's really awesome right

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before we didn't even know if they could

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persist in Wars analog systems but it

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looks like they both evolve and persist

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there for long time scales

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this metabolism may have evolved in

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these environments and then uh prior to

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dispersing around the world via

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acellular and microbial dispersal and

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studying for core reducing organisms in

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Mars analog environments can give us

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further insight into how life may

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persist on the red planet uh when we're

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studying life forms that do metabolisms

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like what we expect to find on Mars we

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shouldn't be looking at organisms that

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come out of the Potomac River we should

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be looking at at organisms in these Mars

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analog systems so I'd like to hear some

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some people I'd like to thank so my

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funding which is the the NSF grant for

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long-term ecological research at McMurdo

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Station uh my department at Brigham

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Young University as well as the help and

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advice of Dr John Coates at UC Berkeley

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Dr Kendall Kendall Lynch at the lunar

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and planetary Institute and Dr Jennifer

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[Music]