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you

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[Music]

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thank you for coming to my talk so my

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system is a little bit different we've

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been hearing about a lot about hot

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spring systems and so this is a

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terrestrial weathering system so I would

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just like to start out by framing this

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in astrobiological context so this

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classic paper here basically did free

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energy calculations for the weathering

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of iron-bearing silicate minerals such

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as Bay Li or Pharaoh silly and you

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actually could have based on this the

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free energy of these reactions alone

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produce an estimated 20 grams per cubic

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centimeter of biota over Martian history

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and while that is you know less than you

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would predict basic first photo trophy

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it's also not entirely inconsequential

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so press it like you mean it they

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weren't lying

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oh so so we also know that microbes are

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able to directly access the iron that is

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found in the silicate mineral lattice

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for an energy metabolism and this was

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demonstrated very beautifully by my

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advisors lab group prior to my arrival

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at UW and what they showed was the

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microbial left the trophic oxidation of

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the structural iron in bio type so that

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was the intent by current tracking the

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in growth of cells coupled to the

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oxidation of iron as well as consumption

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this was done under nitrate reducing

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condition so this is also coupled to the

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the decrease in nitrate but what was

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really elegant about this study was the

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actual demonstration of what's going on

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with the mineralogy so there was also

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this all this beautiful microscopy and

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spectroscopy that went into this and one

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of the interesting things that you see

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is actually the expulsion of iron oxide

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nanoparticles from the bio type um from

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the bio tight structure and that could

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be a result of the charge imbalance and

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then subsequent expulsion of of that so

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putting all of those things together the

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proposed mechanism or proposed model of

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this was a direct enzymatic attack on

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the mineral surface and that's in

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contrast to a a abiotic dissolution

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process whereby you would have an iron

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moving into solution and then subsequent

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utilization of that so this was proposed

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to be a direct enzymatic attack mediated

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by wrong button mediated by outer

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membrane proteins and we will get into

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those a little bit later so I wanted to

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take this to the field I want to define

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an environment of perhaps where a

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process like this would be would be

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relevant so humor me for just one second

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I am not about to tell you that I think

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Mars is made of granite diorite however

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this is the rio blanco quartz i write of

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the wiki amount ins in Puerto Rico so

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this is a extremely rapidly weathering

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granitic system but we have what we have

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is appreciable weight for sense of the

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iron-bearing minerals biotite and

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hornblende and so this is a picture of

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it that was exposed by a landslide and

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you see this beautiful Serota weathered

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weathering pattern that is very typical

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for a granite and what's driving this

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coincident coincidentally enough you

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know this weathering pattern is actually

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the first step in the weathering is the

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oxidation of the structural iron in the

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mineral bio type convenient so this is

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weathering very very rapidly even for a

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granitic system and so there's also

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evidence based on this paper from

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heather bus 2005 at all i'm sorry the

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rest of you that there may be less a

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trophy involved here i don't have time

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to go over it but there's a really

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beautiful reactive transport model

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coupling the the availability of iron to

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the to the in growth of cells but what's

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interesting to note here is that where

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you have high concentrations of

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extractable ferrous iron you also have

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high concentrations of cells based on

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both direct counts and extractable DNA

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so we set out oh nope sorry

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so consensually you can think about it

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like this so here is a core stone that's

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been exposed by a road cut and if you

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know anything about geologists it's that

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we love road cuts because otherwise you

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wouldn't be able to see something like

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this so this conceptual model would

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actually be taking place at

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they between 5 to 8 meters depth and so

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you have an altered bedrock which looks

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like this and on top of that you have

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those those that that kind of onion skin

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peeling structure term the rhineland

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zone and that's where all of your

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pleasure places in your the hornblende

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weathers out and does not persist in the

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overlying Sacre light and the satellite

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is variable in thickness here between 5

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& 8 meters so the idea is you have a

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heterotrophic Li dominated community at

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depths in your surface soil and then you

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have where those high cell densities are

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again a chemo little autotrophic Li

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dominated community that is driven by

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the oxidation of iron in iron in the

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silicate mineral an interaction with a

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direct outer membrane protein or a

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direct enzymatic attack so this is the

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idea that through this process these

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microbes are playing a direct role in

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the conversion of rock to regolith okay

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so in June of last year I went to Puerto

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Rico

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and did some sampling we hand or hand

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augered three cores to the depths of

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auger refusal which was taken to be the

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bedrock satellite interface and the

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deepest point was 700 yes 785

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centimeters and we collected samples

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down at the satellite profile for

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microbiological and genomic analyses and

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this is you know how it how it looks

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like or what it looks like all right so

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just to kind of retrace what Heather did

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I actually wanted to know are b-cells

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active right do we just have dead

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dormant cells accumulating at the

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bedrock satellite interface and to

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answer that question then we did a TV

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bioluminescence assay measuring the ATP

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and if you remember anything from high

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school biology it's probably that ATP is

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the energy currency of the cell so I

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think is a beautiful diagram where you

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have high concentrations of Fe total

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iron total and that's by dilute HCl

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extract attends to the ATP tends to

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track that very very nicely so this is

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great to see not only do we have

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you know increased cell

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just by direct count but these cells

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actually appear to be active I also

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established enrichment cultures for

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these using the whole rock granodiorite

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or the constitutive minerals of inert

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again and again called that one so

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hornblende biotite and then also the

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other major phases being all by in

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quartz so so they got rocks they got

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groundwater and they got carbon dioxide

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and then we track them with overtime and

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for simplicity and for brevity I will

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only talk about the dire right

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enrichment cultures because this is home

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cooking to these microbes it's their

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actual native environment so what you've

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seen with time is after or so we're out

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to 172 days these are still ongoing

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they're not done yet I should probably

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sample them again is that in two of the

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two of the sexes a and B so the a B and

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C correspond to the material collected

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from the bottom of the three separate

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holes

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it appears that there is actually acts

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addition as measured by the FE 2 to Fe

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total ratio and then there also appears

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to be the generation of ATP in these

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cell cultures so it looks like you have

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the generation of ATP coupled to the

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oxidation of of iron in the rack so this

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now moving on into a little bit of

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metagenomics so you may be tired of

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hearing or office systems already

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however these are really important

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systems before for licit OFI these extra

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cellular electron transport reactions so

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in the last top nathan spoke about this

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more about this type of system the poor

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and cytochrome system whereas i'm going

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to talk or focus more on these side c2

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type systems because that's what seems

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to be abundant here so the model

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organism for this is the civvies io

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bacillus farrell oxidant and what you

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have is the the membrane soluble protein

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that then is embedded itself no need for

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an extra pourraient and you have you

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know that oxidation of the

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and then the electrons are transferred

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to a carry plasmic either another

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cytochrome or in or some other electron

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carrier in the period plasm so in my

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metagenomic analysis I found I see two

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homologues several several of them and

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so probably so this is fine seven seven

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of the top twelve taxa actually have a

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homolog to decide to and so up top these

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are gene maps the model organism is a

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city thio bacillus arrow accident and

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the brown is the actual size situ and on

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the end terminus here is the number of

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heme binding motifs and on the

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c-terminus here is the number of

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transmembrane domains and in a city thio

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bacillus arrow oxygens you see it's 1

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and 18 and then next to that you will

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find a Oh apparently I'm missing a

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number there's a human a motif in this

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peri-peri plasmic cytochrome so next to

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that you have a periplasmic cytochrome

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to receive electrons from from this IC 2

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and so all of these these first side

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here are beta proteobacteria these are

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not particularly canonical iron

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oxidizers however it's not you know

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entirely unreasonable to expect

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something like this particularly in a

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Cooper avetis there's known other an

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oxidizing to previous taxa what's

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actually interesting to me here is these

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Xiamen Simona de CA they're gamma

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proteobacteria and in this case you know

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it has the periplasmic cytochrome but it

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also in another case has a rather than a

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cytochrome a high potential iron sulfur

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cluster and we also see that in one of

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these kibriya Vettes strains so to quote

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my advisor who quoted or to quote nathan

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who quoted my adviser when you see real

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Bisco and eet together in one

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metagenomic then it's kind of a smoking

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gun for lift a lot of trophies and that

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it appears to be what we have here so

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just to wrap this up i would like to

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revisit this conceptual model that i

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laid out earlier so we have

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the rio blanco quartz died right on top

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of that we have the satellite and we've

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demonstrated that not only are there

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cells there but they're also active

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right so this is a good news we have a

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active microbial community institute and

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then also in enrichment culture we have

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demonstrated that there is a parent

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coupling of the oxidation of iron to the

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generation of ATP at but then the

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smoking gun in all of this was that

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interaction with these outer membrane

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proteins and well there you go

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we have cycie to homologues in a fairly

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considerable number of taxa within these

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within these and cultures so it does

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appear that this idea that rocks or

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regolith is catalyzed by bacteria does

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actually hold so i would just like to

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thank my collaborators as well as the

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u.s. Forest Service and the lukio

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critical zone Observatory for logistical

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help sampling these and then my funding

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sources the NAI and Department of

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Geoscience at UW Madison and I have time

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for some questions thanks Stephanie do

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we have any questions so I've got one so

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at what point in that sediment column

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does it go in aqsa can do do you find

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evidence it doesn't it does not know

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it's above the water table so this is up

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on a ridge it's not even subarctic

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okay any additional questions okay so