Professor of Environmental Sciences at Rutgers University. I've known Kat since, well, for a while. So she was a grad student in Jen Magalotti's lab at Penn State, which got her PhD. She did some caving in Italy to sample sulfur oxy-sizing microbes and really published her papers. Anyway, she did her undergrad in chemistry. She's a chemist at heart, although multi-talented, as I'll say. She did her be in chemistry at Galter College, PhD in geosciences and biogeochemistry at Penn State. She had a couple different postdoctoral fellowships at Caltech, and then joined us on the East Coast again at Rutgers. She is a geobiologist, she's really, I would say, the reference geobiologist, she does fieldwork, she does culturing, all sorts of really, this is really what she's known for detailed, difficult analytical chemistry. Developing methods to really enable us to do more things. Microscopy, microscopy with manasomes, et cetera. The list keeps on going. Are there any methods you can't do? I don't know. I haven't used an NMR in 20 years. so she's also similarly has excelled in a wide range of different geobiology topics for her sulfur work her carbon work um carbonate and talk to us about nothing so maybe a little bit less about methane and a little bit more salty environments and different types of metabolisms. No, no, it's totally okay. I feel like I've been in the methane for a long time. And yes, maybe hints of methane metabolism, or maybe not. But thank you, Clara. And thank you for having me and letting me reschedule to be here. And so one of the things that I've worked on since early on in my PhD at Penn State has been looking at these really kind of charismatic, brightly, super salty environments. And here is the Great Salt Lake in Utah, right by the kind of spiral jetty art piece that's installed there for display. And this is a, it is one of those pink landscaping flags you can see, or hopefully you can see on the video, that the water is nearly the same color as our pink landscaping flag from this um halophilic bloom that's a mixture of haloarchaea as well as as well as the eukaryotic algae vanilla and possibly other things in that mix too and so these these are environments that are just really really kind of exciting to look at and there's a diversity of these super super salty environments and so and the diversity of the pigments and the organisms that we can actually find there and so here just just to have like a picture show a little bit because who doesn't like pretty pictures you can have alkaline super salty places and so this is Tanzania and Lake Natron here's a gypsum crystal from Guerrero Negro in Baja, California and Mexico and then these are those these are the salt ponds off of the San Francisco Bay, that if you've flown into San Francisco at the right time of day, possibly you've been able to see these out your window. And every single one of these is properly hypersaline, but the difference in pigments is kind of reflecting the difference in the organismal populations that are taking over in these locations. And so we're talking about places that are like super, super high sodium chloride. These are like 1, 2, 3.5, possibly even higher to the saturation point where you're going to start just having this all fall out in sodium chloride. There can be other ions that are also in very high concentration, obviously, like magnesium, potassium. Sometimes you're even getting quite high concentrations of calcium in these places, too. and some of them are in these alkaline pH ranges, but you can also have acidic brine locations and you can have anoxic brine locations as well as these oxygen open to the air in our camera -taking abilities locations here. And these particular ones are also at a high UV stress. So these are multiply stressed environments in terms of the types of things that organisms that are making their habitats here have to deal with. But really, I think that the big component here that makes them special is dealing with this osmotic pressure of the really, really high salt concentrations. And so there's adaptations that these types of organisms have taken into themselves to deal with this. And so there's a lot of organisms that have various transporters to either pump salt in, so they'll actually increase their internal chloride concentration and do a balancing effect by exporting sodium and potassium, exporting calcium, these various things to do a balancing effect from the osmotic stress of the external environment in order to maintain that maintain themselves from being laced and losing all that cellular water within the cytosol. There's other organisms, particularly bacterial halophiles and eukaryotic halophiles that will actually pump in lots of organic solutes to do the same type of osmotic regulation and balance. So there's these kind of unique adaptations from a physiological perspective that are requiring a lot of energy in order to maintain these processes to stop things. And so those are these kind of two general strategies of organic inverse saltin, in addition to kind of membrane modifications and also just an adaptation for all the salt to having amino acids tend to be a little bit more in the acidic residue classes than in other ones. So there's a lot of different kind of physiological strengths and stretches here. As someone who really has worked a lot with archaea more so than more more than the halophilic bacteria over the years i'm really more interested in the adaptations that are going on over here and some of these are really really cool in in the in the sense that they're actually using light to drive these pumps and so they're not photosynthetic organisms but these these pumps are are are light sensitive and the entire adaptation to this osmotic stress and the salt pumping strategy is highly light dependent and so So you can see these four different potential rhodopsins that are being described here, a bacteria rhodopsin, a halorhodopsin, and two sensory rhodopsins. These each might be targeting slightly different wavelengths of light. And based upon what the actual configuration of the rhodopsin is, they may also be doing different types of pumping about what's going on. And we've really not necessarily fully explored all potential rhodopsins that are out there. And from a biotechnological perspective, which is really outside the scope of what I'm talking about today, there's possibilities for managing these types of pumping systems to make them work for other ions that are not the ones that biology has naturally evolved to deal with. But in this particular case, bacteria rhodopsin is mostly a light-driven proton pump, a halorhodopsin, a chloride pump, and the sensory rhodopsin, several of them are actually kind of associated with calcium and magnesium pumping and other things like that, as well as other things out there. And so that's a lot of how the energetic stress of being in this situation is handled by these telophilagarchia. So just to kind of show those in like one more detail, you can see this particular channel of Dobson doing multiple different things. And it's a zone of interest, I think, particularly from the biotechnology people who are, you know, it's exciting to have something that you just shine light on and it does this work of doing ion separation for you. So we went out in 2018 to both the Central Valley in California, to the soda lake that was out there, as well as to the Great Salt Lake, and collected a bunch of samples as a team that was looking at how halophiles, in addition to doing some of these light-driven pumping things, might also have extracellular proteins that are associated with either salt nucleation, or potentially ice nucleation, you know, maybe the maybe the dust blowing off the Great Salt Lake helps establish those nice snowy fields in Park City. At least that was the idea of my of my colleague Moshe Rhodes here, who was the big proponent of that aspect of the project. What I was really interested in was looking to see if we could capture some new or new to us halophiles from these types of settings. And so we brought back lots of bigger water samples to the lab. I had a senior thesis student, Michaela Byron, who plated lots of stuff out. We were able to pick colonies and get lots of different things growing. And as it turned out, halorubrums, who I think are one of those kind of lab rats of the Salt Lake Seine, were acquired from both the Spiral Jetty location as well as this sort of way. that she did lots of growth courage with for us, temperature with sodium chloride concentration with pH things. And so there's differences between these two organisms that we have that are both halorubrim that span the range of what their salt tolerances are, what their preferred pH levels are for growth, but they're interesting organisms with which to do more work. And one of the things that we started noticing on a very anecdotal level as we would do this is that Michaela would make media and she would sterilize it, tap the bottle, leave it on the shelf, and that media could stay for months, months, and you would have no salt precipitation going on in that media whatsoever in a closed bottle or even in a bottle that wasn't perfectly closed. But the moment we inoculated a culture, we started to have big, big salt crystals popping out of solution at all times. And so this is not necessarily like a super surprising thing. You introduce microbes, you're introducing nucleation points into these types of settings. But it really was kind of like an interesting thing. It wasn't an evaporative driven process. It clearly was, if we have these cells in here, we let things sit for even very short periods of time, we start to have big, pretty obviously, halite-looking crystals forming in our type of genes. And so my grad student, David, has been working over the past couple years to explore this type of process and to think about, is there any biogenicity that we can think about with these types of halite crystals that might be forming these types of settings? Because this gives you a nice mineral -based proxy for life in salty environments, which is certainly something that I think is of interest in the broader astrobiological community, but also may have interesting implications for looking at mineral successions if we go back in time to evaporated basins and think about what's going on in those types of locations. and so what we do see is that if you um inoculate a culture uh and you take a dropout and you start counting the number of crystals that are forming over time versus the control thing we get more crystals we get bigger crystals we get faster crystals if you have cells there yeah i'm a so how do you how do you make a control but what is it so it's just our salty media and we don't add cells to it okay and so we've sterilized it with uh either an autoclave uh or we filter sterilized the media through um 0.2 micron filter um one way or another i think in fact the 0.2 micron filter which is what we've mostly switched to also does a lot of eliminating any small particles that might be residual so in this case we're making our faux brines within the labs that we can control all the kind of chemicals that are in there yeah no it's a great it's a great question and we could certainly think about doing something like this with a natural water sample where we would have less control about what the carbon component is but we would have like we'd have a similar type of chemistry potentially um so so in any case it does seem like that our our observational abilities to say hey it looks like there's salt crystals that are forming more if we add cells is really pretty well held up from experimental work to see that these things are in there and there's something about those cells though maybe there's nothing special about the salt crystals afterwards other than that they're forming quicker um and they do tend to capture biomass within them and so there's a potential maybe on a longer time scale of having some carbon sulfur nitrogen preservation within these halite um crystals within like fluid inclusions that might be in there within just kind of the general crystal matrix. Now, one would think that that actually could lead to some defects that you might be able to, you know, see within the crystal chemistry. But so far, we've not been able to identify that. And part of the reason why we haven't is because in the process of doing all this, we kept running into this situation where it became pretty obvious that more than hell, it was precipitating in our cultures. And David will tell the story but i got really mad at him one day that like dishes were piling up and they weren't getting cleaned and he and he tells me well it's not that it's that i had water and i'm waiting for whatever's in this to dissolve and it just won't go away and i was like well that's really interesting because salt should just go away if we have water in it these are these are things that you know we all know that table salt dissolves and and so my reaction at that point was you know of course that like go grab some hcl and throw it into the mix and see what would happen and and it effervesce so we're more forming more than just salt crystals in here we're forming carbonate minerals um and then that's a really interesting question of what and like what carbonate minerals are forming by this halophile process of maybe this rhodopsin based pumping that's increasing the, um, uh, increasing the, the, the, the omega value for some saturation state for ragunite, magnesite, dolomite. Um, and indeed what it really does look like is that we are forming something in this dolomite pathway. Um, and so, uh, using, using the XRD, um, we're getting magnesium carbonates and and david here has identified everything here with dolomite but i think it really does lend itself to the question of where on the dolomite to um i think i got this in the wrong order i think it should be dolomite huntite and magnesite in terms of like how proto-dolomite you are but um and that's really just kind of about a hydration state of this kind of mineral are all magnesium calcium carbonates and some of them just have a lot more water associated with mineral. And so it's on this spectrum of eventually maybe diagenetically becoming dolomite. And these are things that are precipitating in the lab in a month timescale, less than a month timescale, perhaps, but, you know, got to get big enough that you notice it. And, and they're, they're, they're, they're being done by an aerobic organism, an aerobic heterotroph sitting at room temperature and pressure and just doing its thin and causing this noticeable accumulation of a carbonate mineral. And we've done more at this point, because we pivoted, you know, as one does, because this is a more interesting story, but why are salty grinds producing carbonate minerals? And so we can see these proto-dolamites, They look like what they should. They range from these kind of like small crystals to much larger ones as time goes by. The weight percentage of the various elements is making sense. We've run them on the EA also, and we've seen the same kind of thing. And none of this necessarily makes sense from a brine chemistry perspective, because nothing about our brine chemistry suggests that any carbonate minerals should ever precipitate. These are unbuffered media, so there's no bicarbonate or carbonate thrown in here in the first place. So any carbonate ions that are being formed are a respiratory byproduct of the sugar metabolism of our cells here. The magnesium and calcium concentrations, while high, are not necessarily high enough that they're going to be the thing that should be the dominant crystal that's precipitating out. Indeed, if you look at things, sodium chloride really is the only thing that should be predicted to fall out of here. But we now know that we're seeing the halite for sure always. We're seeing these magnesium calcium carbonates, and we also see gypsum to some extent in some locations in here too. So these cells are producing an assortment of different things, including this dolomite or protodolomite carbonates in our cultures. and so this is not the first time somebody has noticed this because there is this kind of like question out there about what's going on with dolomite because we don't really have any very good modern examples of lab ways that we can generate lots of dolomite but it's a really abundant mineral and rough record and so it's it's every time somebody noticed it for me in a microbial culture we get usually there's a paper that comes out that notes something about it because it is it's an interesting thing to come up with ways that we can do this and so previously we've had aerobic heterotrophes uh methanogenic archaea sulfate reducing bacteria uh halophilic bacteria and so this this would be kind of one of the first instances of somebody reporting a halophilic archaea doing this also and so so there is evidence out there about how this might be going down and and the general general thought to some extent is that there must be creating micro environments that are favorable to precipitation because the overall brine chemistry in most of these things doesn't really necessarily respect that it would sit in a place where you would expect this. And so you've got your cells, just like we would think about if we were talking about cyanobacteria and carbonate, then the calcetic sheaths forming around them. You're creating these micro pockets where the negative charges of the cell chemistry, potentially these pumping mechanisms that are light-driven pumps. All these things are combining together to create this microenvironment space that's favorable to this process here. And that's what we really do think is happening, is that it's one of these channel redoxidants is sitting there and creating this imbalance in a near-cell zone that's giving us the saturation of the calcium, and that's in proximity to where the respiration of ferric sugars is happening. And we get the situation where we can actually get these proto-dolamites forming. So if this is our hypothesis, we have a really good way of testing. If we think this is light-driven, then we can turn off the light and we can see what actually happens. And so this is where things get more complicated because we're, of course, dealing with trying to measure ion concentration changes when our concentrations are so high that it's very difficult to necessarily see changes, but we do think that we are able to see stuff, and so in this particular case, we've got a yellow light experiment, a black dark experiment, and our green is our control again, this uninoculated sterilized media that's there, and that one is a little bit more confusing for discussion about what's going on. But between our light and dark, we can see this obvious difference of extra chloride pumping potentially to, in the light experiment, extra sodium pumping outwards. And the chloride one, I would be a little bit more wary of over-interpreting in the sense that we're really dealing with such high concentrations there. But the difference here is a little bit more substantial and recognizable. Then if we actually start looking at, you know, what's going on in terms of the actual appearance of these things, we can see a pigment difference in these light and dark cultures. It becomes pretty obvious pretty quickly, maybe less so in the right image at this point. But here you can see much more of this pink rhodopsin coloring here, and there's an absence of it in this case so something something has changed in in our cultures and i seem to have i seem to have missed so i probably am going to find that i've accidentally slid some other slide down someplace else in this talk but one of the things that we also did look at is this change of the magnesium and calcium ratio over time and what you do see even though i don't know where i put the figure at this particular point is that the magnesium the calcium ratio is increasing over time in our light experiments, but it's not increasing in our dark experiments. That is exactly the kind of thing that we would probably expect if we're generating via this pumping system a way of getting this there. It's so confusing. What happened? I'm going to pause for just a second because I've got to figure out where. I think I've accidentally rearranged that. Oh, that's weird. I'm not really sure why it skipped a slide, but there we go. There we go. This is what I was talking about there, where we can see versus our control that there's this kind of decrease in calcium over time, decrease in both calcium and magnesium over time. But if we're looking at the ratio specifically, we can see this possibly over the arobar trend where the magnesium to calcium ratio is increasing and that's the kind of thing that you would actually expect if you're kind of moving into this system where you're setting up the um the brine chemistry for these kind of dolomite precipitates and i'm not really sure why that one dropped out before and now it's done it again huh that's so weird it keeps on showing me this one slide that is not the next slide in order um i don't have an explanation for that But so the final thing that we've done with this project, and then we're working on kind of finishing up the last bits of the carbon isotope work on this, is where is the carbon coming from? I mean, so the obvious answer here is that it's probably coming from the sussanate, which is the sugar that we're feeding these bugs, which sits at about negative 27 per mil in carbon isotope space. And so my anticipation would not be that I would get carbonate minerals that are necessarily negative 27. they should be lighter than that because or sorry they should be it's a good question they could they they i actually probably would anticipate them to be that or potentially maybe even a little bit lighter than that as a respiratory byproduct of that and instead what we're seeing is uh this 8 12 20 24 month carbon carbon iso for these dole mice that are in here or well carbonate pool in general because if there's if there's any other kind of carbonate phases, we're not necessarily separating them out from each other, but we're seeing them have more atmospheric values. And this is an interesting question as to why they're at this level. One of my thoughts at this point is that the really high ionic strength of these brines that we're dealing with is somehow causing an enrichment in the CO2 pool within there, and we're losing more of the light carbon and there's something about the chemistry of the brines that's holding on to the heavier carbon. And I think there's a little bit of modeling work to figure out exactly if that makes sense, but that's at this point my best guess because I don't think we're actually fixing CO2 from the atmosphere. I do think that this is still a respiratory byproduct and we've addressed this recently by running the same set of experiments again, but with a 13C labeled glucose substrate to just see if we can track it down through there and make sure that it is the carbon that will feed it up. Now, I get from also, again, stretching out to a biotechnology perspective, I think that this represents kind of a really interesting concept of a project that I pitched to the room and, you know, will hopefully pitch further in other environments at later points in time. And then if you have a desalination plant or a salt crystallization plant, you know, you're inherently making these super salty pools. These bugs, we know from other work that I've done with my colleague Matthew Rhodes, who's at the College of Charleston, if you've got things open to the air, they will eventually colonize open rainfall. There's enough transit in aerosols and dust particles that you will eventually colonize if you're anywhere near a source of a salt marsh or places where these organisms might be. So you can get them there, or you can inoculate them indirectly. And so this presents an interesting kind of low cost carbon sequestration concept where if you have your brine and you've got sugar byproducts or whatever, organic byproducts, you could feed organisms and potentially have a way of getting carbonates forming in these types of locations. And that's very much the thing that we need, some proof of concept. And I think that these experiments are kind of leading in that direction, that this is something that you could offset some of the work of desalinization and the carbon cost of that by incorporating maybe other uses of the salt pools that you're making. Okay. And now is when I actually wanted this slide to pop on up. And so with that, I want to move to a totally different salty environment. And this is, I don't know, really kind of become the theme of my recent work as these super salty brine pools. And I'm going to move offshore to a brine pool in the ocean and these possible signatures and methanotropy. And before I go there, because we're going to talk about hydrogen isotopes, I just want to make sure that everybody's on board with what's going on with hydrogen isotopes. And so in this particular case, we're talking about this difference between the hydrogen-1 and the hydrogen-2, so protium and deuterium. They're the only ones that get special names as isotopes, but lucky hydrogen. And we're not talking about tritium, which is the radioisotope. And what we're really doing is we're looking, and we're also going to look at oxygen to some extent, But we're looking at how these hydrogen and oxygen isotopes in water vary with metabolism that's going on. And so this is going to all be reported in a delta notation, same as the carbon stuff that I did. But we're looking at the hydrogen thing, and it's going to really kind of tell us how much our samples are deviating from the standard. In the case of hydrogen isotopes, we use a mean ocean water value as our zero point. So you can be heavier than mean ocean water, which would probably be some sort of evaporative process that got you there. Or you can be lighter, which would be the evaporative product as opposed to the evaporative leftover stuff that's in there. Water itself has lots of different flavors, which is fine. Not all of them are very abundant, but you can see you can mix and match your heavy oxygens and your heavy hydrogens to get lots of different possible ones out there. There really are only a couple that are really kind of interesting to consider because they're the only really abundant ones that are there. And the cool thing is that water, being one of those kind of greenhouse gases, you can actually use infrared light and look at these symmetric stretches, bends, asymmetric stretches is the other one here. And these types of different movements of the water molecule bonds lead to different spectral absorbance bands in these infrared wavelengths. And that's really cool because that means that we can do isotopes without a heavy-duty magnetic sector instrument and at a lot cheaper cost. And that's always kind of like a nice thing to do. And it's also something that really could fit on the back of a pickup truck or on a lab bench going out to sea. And so this is all being done with the Taro. It's a cavity ring down system with lasers that are looking at these particular bands. And so you can see as you switch from a hydrogen to a hydrogen for deuterium or two deuteriums, you get a full shift where these major wavelength, where these major absorbance bands are for these various stretches. And it becomes more apparent in these other ones here associated with the bands. So this is really cool. And where have we used this in the past? So this is a really interesting way to, for instance, track methanotrophy, because you make water as a byproduct of methanotrophy. And so this is anaerobic methanotrophy. Don't fixate it on the major kind of like pathway. But if you wanted to look at it later, you could see where each of these hydrogens is potentially coming from. And you can actually see if you label your methane with a heavy deuterium, you can see that deuterium track the rate of methanotrophy over time. And there's really not that much of the hydrogen incorporated into the biomass. It's either going into water or kind of circling back around into some of these various enzyme byproducts. And I'm remembering right. I think that, yeah, so it's about 50 percent of the water pool will be holding on to that methane hydrogen that's popping off of here. You can also do this for aerobic methanotropy. It works the same way, where here you actually even have to adjust your rate calculations because the deuterium is actually a little bit more of that water pool that's being generated from these reactions, but similar ratios for type 1 and type 2 aerobic methanotropes. antitropes. And in this particular case, some of that hydrogen does actually get assimilated into the organism. So they will also actually pick up some of that heavy hydrogen. So this is just kind of like a background on how one can do something like this. But you could imagine other questions that have water as byproduct of metabolism, where we can think about where does the hydrogen come from? And how can we look at it to think about rates of different things? And those are other questions that we could answer. So we took this type of question, just incidentally, to a brine pool location that has a huge concentration of methane in it. And so this is Orca Basin within the Gulf of Mexico. Orca, because I think it vaguely looks like a whale, I think that's where the name is coming from. And so this is an anoxic hypersaline basin. So it's a slump that where the slump exposed some Permian salts. Permian salts dissolved, created a really, really super salty bottom water condition. And so there is a really strong chemocline where the density has a dramatic shift. And you go from oxic waters to anoxic waters. And pretty much anything that is below this level is kind of in a pickling brine. Stuff above it is not. So the density is radically different. The salinity is radically different. and the redox conditions are radically different and the preservation is is pretty incredible so within the sediments here i mean there's at least 1600 year old sargassum so this is stuff that you could punch it and it looks like sargassum was on the surface of the ocean it's it's extremely well preserved it's very well pickled and so we went here and the question here uh is and the rationale for going to this location is thinking about these anoxic basements, again, as a location where if we're going to try and throw carbon into a deep hole and try and forget about it for some period of time, these are the kind of places that venture capitalist companies coming up with these types of project endeavors are really targeting. And so there's a good question about, is this a terrible idea? And can we do some background experiments first to see what's going on in these systems before we start throwing things in the hole and hoping that it never comes back up and one of the big reasons here where it's really important to think about that is this chemo client also represents again it's really high methane concentration at the bottom we don't want that methane kind of bubbling up to the surface oceans which would not be a good idea okay so there's multiple cruises between 2023 and 2024 I only went on one of them with them which was really fun um and so here we are casting the ctd we managed to get a bunch of multi cores also so we use some sediment characterization and with the ctds we have lots of water samples for water chemistry but then also looking at these water isotopes one of the reasons why we're considering the water isotopes is we might want some ways that we can track processes of this respiration of new carbon that's getting thrown in the basin and there might be a way to do it or to see if we're suddenly stimulating lots of methane oxidation by the water isotopes and so indeed so the salinity is pretty much following your the sulfate of the methane profile too but i'm not showing it here um so you can see that the sulfate concentration is rapidly jumping up in in this brine pool to 45 millimolar the methane is is absolutely astonishingly high this is probably a low -end estimate because Methane is notoriously hard to measure from water samples in these kind of conditions. So somewhere in the range of nearly half a millimolar. And we interestingly are seeing at this interface location, this spike downwards in our hydrogen isotopes that are here. And so this is not a label experiment. We don't have labels. We're just looking at the natural conditions here. One of the things that we would expect of biogenic methane, which is what the methane in this location is, is hydrogen isotope values that are substantially more negative than our average water sample. So our methane in here can actually act, maybe, as a natural tracer of this methanotropy process. Now, this could be a one-off occasion that we got lucky and we got some one set of weird samples. Maybe they evaporated. Maybe something weird happened to our samples on collection. But we've actually had multiple cruises and multiple CDDs on multiple seasons. And this seems to be a pretty kind of robust, a little bit in flux signature of what's going on at this interface layer between the brine and the above water column. We're having methane basically disappear as we get into the brine level, and we're seeing this really negative spike where negative trend line within the water isotopes. And it recovers both above and below. And this could be indicative of a zone of intense methanotrophy, which would be a really kind of unique thing to actually be able to map it in a natural setting. and probably only is possible in this case that we've got so much methane and a restricted circulation within this type of basin. But it's also possible that the hydrogen shift isn't to do with methane. And to be fully honest, we have to consider some of these other possibilities that are out there. And there are other good possibilities too. So it could be methane oxidation. But we also have to think about the fact that we're taking our dissolved organic matter and our various things in the system and we're running them deep into the water into pressure and and this dissolved organic matter is going to experience some level of condensation over time as it's aging and getting through the water column and so we could just be losing water from our uh from our organics um it could also be water release due to this kind of pickling situation where you know you squeeze out the water from the organic and you're replacing it with that saltier brine and so we could be losing water from the surface waters now of course I would say in both those cases, I think our isotope excursion is going the wrong way for that to make a really kind of sensible explanation because the surface waters of the Gulf of Mexico are actually a little bit positive because of the high amount of evaporation. So you actually have waters that are above zero in some parts of the surface of the Gulf of Mexico. So I don't know that that necessarily would explain it easily. That being said, what could explain it is looking at other biogeochemical processes that are going on. And that could include manganese or iron production in the system. And so both iron oxyhydroxides and manganese oxides release water as they get reduced. And so we could actually be looking at an alternative, but still biogeochemical signature for this water excursion that we're seeing in the water columns. And I think that This is an interesting site to continue exploring for a number of reasons, and one of them being that if we actually start looking at the sediment cores, this red material that you're seeing here, this is all iron. It's not biological. It's super salty, but it's all iron. And so, in a way, if you've ever seen a picture of abandoned iron formation, this is like the Jell-O version of abandoned iron formation. And so there's an interesting question about how this environment is getting to this point that you have so much oxidized iron accumulating in these kind of deep zones, lots of sulfur, lots of sulfate, no sulfate reduction. And is that entirely because it's inhibited by the high salt? Unclear. You know, there's a lot of microbiological questions still to go on here, and dealing with these salty conditions and how are these responses going on. There are halophilicartia living here. They're obviously in the dark. And so we don't know what their role is in any of these kind of processes either. And this is kind of where this work is going. And with that, I'm going to just, you know, thank everybody for their help on various projects with my, with the Califile Culturing Project, as well as the Orca Basin Project. And I'm happy to take some questions. Yeah. So, so that was super cool, that was both interesting. So when you're thinking about these processes in the kind of these cellular pumps that are kind of driven by light, then and we have these experiments in the lab, you're looking at changing the life conditions. If you translate that to a natural system, do you think you would like light is limiting enough so that you would see big differences, say it's a solid between the summer and the winter season? I think your bigger issue with the summer and the winter seasons is that you have the season where you're actually importing, occasionally at least, a freshwater lens on there, which might also have an influence on who's living where in there. I'm not sure. I think that that would be kind of worth looking at, going out, collecting filters, or seeing if there's a difference in minerals that are in the particulate collection that you get out of the water column. Or, I mean, I think there's certainly kind of a transcriptomic question about what is the light threshold at which you stop doing something else. And that's not been something that's necessarily in the picture for us as a lab right now, but it's something that I think the project could go forward. Yeah. So when you have a complex of freshwater, What you'll usually have is that there's the cycle of the algae, the eukaryotes, the bacteria, and then the archaea, thinking over. The archaea tend to be the ones that are the most able to sustain themselves in these super high salt environments. So the freshwater comes in, and you'll get this Daniela bloom, which is also red. And so everything's red. but so they bloom and they actually tend to make a lot of sugars just just a huge amount of sugars from from all the photosynthesis that they're doing that as they die off as it gets salty because they'll hit a threshold that they can't sustain it anymore they get just consumed and support this bloom of the halophyllic archaea and bacteria and so you get these people said probably you have some suppression of them just to shade it out or out compete it but i think that you know, they're hovering and waiting for their opportunity to just totally glim up again. Yeah. Also, in this project, you were arguing that the dome light was spinning up with the conditions that were produced by these plants. But when you turn off the lights, you're also just making these organisms a lot less healthy, right? Yes. They're not being able to do anything. To what extent is that the explanation and several related questions. You said that this happens, it only is it accumulating over the course of a long time. Is that fast? I think, is it fast? I think the answer is yes with respect to low temperature, low pressure. How do we make dolomite in a lab? I think that definitely it's fast with respect to that compared to quickly can a cyanobacterium and calcite. It's probably not that fast, but I think that these things are growing at a slower growth rate than maybe a really happy cyanobacteria is. The light thing, I'm not, I think the answer is it could be either, but they're in some ways addressing kind of this question right like is if you're unhappy because you're living in the dark and so you're pumping now costs you more atp um than it would if you had this extra energy light um you're you're still kind of in that same thing is it the light -driven pump that's causing this or is it just a slowdown in metabolism and access the light-driven pump and i i think it's a tricky one to decouple and And I'm not sure if anybody has any knockout files at this point. I don't know how hard they are to make, but I think that there are ways to address the question. It's just a matter of, like, finding the right tools. So as you were talking, I was thinking, well, in the lab, you can give them light or dark. But in nature, they're getting both all the time. Yeah. So how does that play out in the world? I mean, I assume that what you're seeing then is that you are using ATP at night to sustain yourself, but you're creating via that kind of, probably specifically that proton pump and letting them slowly fall back in for some ATP synthase sort of thing. You're probably making up ATP in the daylight hours to support whatever's going on at nighttime. I'm starting to think like, well, you could control it in the lab, and then there's seasonality. I think that's what happens then. I think in the field, you're just saying, we know that you do this, do your best if you're letting them go in the field. Yeah, it's really interesting. In the lab, is the light production cell density dependent to make those little micro -array issues? um well okay so the i yes i guess so because in this in the sense the longer you let them grow and the more dense the culture is the more dolomite is precipicated now i guess that's again it's a hard one to decouple because is that truly a self thing or is it just a time component and i i don't have an answer for that um i think for any question um i mean maybe there's a way with some sort of dialysis membrane or something like that, then we can address that. Yeah, I think at this point, for David's thesis chapter, REM here is this is what we're seeing. And I move from there as to what funding or what stress there might be to proceed with the project in other directions. Yeah. I have a question, and Lewyn. Oh, yeah, Jen. Hi, Jen. And so thinking about the halophiles and how the succinate carbon values or the carbon values of the dolomite change over the length of the culture. And so when you're talking about a very old culture, do you know if your cells are still growing? So, yeah, no, that's a good question. I have not checked if there is any residual succinate left to support them or if they're eating other things in there. And they are able to, so we know because we have a genome, and I didn't put any of that data up here today, but we know that they're able to do some level of anaerobic, this particular bug is able to do some level of anaerobic nitrogen metabolism. It's also able to do a bunch of fermentation. And so I think that they probably are still growing, but they may not be growing in the happy way that they were growing when they got started. it um like the the tca cycle puts off so much co2 that to me kind of looks like this metabolic switch is driving the co2 record of the dolomite and so i started wondering like can they eat other components in the tca cycle and then you could actually watch how much co2 is like being off but i don't know it's probably way too detailed for this problem but yeah but it's interesting to know that they can do other things because yeah it does look like they switched what they're eating so yeah no I think that's a great question and I think that there is um I mean I'm sure there's a way to put together some sort of metabolic flex model and and think about like where where different things are coming from at different points in time um I I think you would be a future student who would be looking at it um at that point in time but yeah I I actually we'll have to think about like we have we have an lc i look and i can see what the ethanol concentrations are over time like if that is something that could be there um i don't know i don't know that i have a good way to get at any of the high scope values of our substrates after we after we start the experiment to think about like is it source um but i can think about the natural patterns of fractionation with different substrates and think if that actually fits it. That's a good thing to consider. Does this biological process of making dilamide leave any signature that makes it salt dilamide in nature to say this came from this process versus some natural precipitation? That's a great question. I don't know that I know the answer to that. I don't know that I have a definitive thought at this point. What I will say is that if you actually do drill, there have been a couple of drilling programs that have gone into the great salt and you do see um there's some aragonic layers within the sediment there but you see lots of dolomite and you see some of these kind of huntite magnesite dolomite things within there and so it is possible that like if you know something contextually about the environment you're looking at and then you start to see this that maybe maybe there is if we're putting things in the right kind of thought process there is to say, this does look like it's a biologically driven process that's getting us to this point. And I mean, I think that that's, it's maybe a future direction for people to consider when they go to these types of sites out there. You want to throw a comment on the interest of some of this to the astrobiology community? Can you say more about that? Yeah. So so if we if we think about places like like Mars, one of the reasons why we got into this was we were initially going to we were initially going to focus on the halite project and pursue an exobiology thing. We're going to say we're going to take a look at can we can we put any kind of biogenic signature on this mineral that shouldn't be that isn't something that we consider a bio mineral. and and it would be something that you could plausibly evaporated settings on mars and then you're creating abiotic record this now abiotic record of uh of some past metabolisms that were there um i and i and it was always kind of like a a question of would that actually work because you know, halite can easily get re -exolved, re-precipitate it, and those kind of things. So it was a good question of, first off, was there any kind of thing that we could say, this halite looks like it came from cells being present, or this halite was just a black effect? And I don't think we ever got to that point before we found dolomite. But I think that this end would kind of go in this other direction of asking the question of, is this tholemite biologic soul. And I think that also kind of sits in with these Mars exploratory things that you don't necessarily have to count on finding a living cell. Maybe there's a set of mineral assemblages that we can see that'll be so strongly indicative of past life that we can convince ourselves. And I think the bar is so high that I don't know that there's any level of proof that we can, unless somebody sees a little green man walking along, they're never going to feel like a little green man is. Are there any questions online? Don't see any. Any final questions? Aaron, who is? Alright, let's think. Thank you.
Kat Dawson - SMSP Spring Seminar Series 2025
From Taylor Link May 09, 2025
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Kat Dawson
Assistant Professor
Rutgers University
Rutgers University
May 9, 2025 at 12:00 PM
Robinson 202 and via ITV Cannon 203
Hosted by James Rising
Abstract: Hypersaline conditions occur in a variety of environments from evaporative ponds, salty veins within sea ice, the Great Salt Lake, and even brine pools inside the ocean. These environments are characterized by salt concentrations that range from 3x ocean salinity to saturation. In additional to high salinity these environments can challenge resident organisms with alkaline pH, high concentrations of other ions like Mg2+, and high UV flux. Despite these multiple stressors to habitability, diverse communities of halophilic algae, bacteria, and archaea populate these environments. The adaptations used by these organisms to survive and thrive have implications for understanding the limits of habitability and identifying signatures of biological activity. Today, I will present results from two ongoing projects that explore how haloarchaeal physiology induces carbonate mineral precipitation and an investigation of how microbial metabolic processes, including methanotrophy, could lead to an observed hydrogen isotope excursion in the water column of a brine pool.
Zoom Recording ID: 93222841453 UUID: bkWmD8oNSIKaEPvtEQ5/uQ== Meeting Time: 2025-05-09 03:42:30pmGMT
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