Become a fan of Slashdot on Facebook

 



Forgot your password?
typodupeerror
×
Biotech Science

Leading Scientists Urge Ban On Developing 'Mirror-Image' Bacteria (science.org) 128

An anonymous reader quotes a report from Science Magazine: It would be a nightmare lab leak: Synthetic bacteria escape the petri dish and unleash a global plague that life on Earth is incapable of defending itself against. That's the concern raised by a group of eminent researchers in a Policy Forum published online today in Science. The commentary's 38 authors, from a broad range of disciplines, argue that governments worldwide should prohibit research and funding aimed at creating so-called mirror-image bacteria whose chemical makeup differs in a fundamental way from that of naturally existing organisms.

All of life's primary biomolecules can exist in two mirror-image forms, like a left and right hand. But only one form is found in nature. Proteins are left-handed, for example, and DNA and RNA are right-handed. Synthetic biologists have previously synthesized mirror-image proteins and genetic molecules. And mirror-image amino acids and peptides -- the building blocks of proteins -- have been incorporated into several approved drugs. Because natural enzymes struggle to break down mirror-image biomolecules, these components help the drugs survive longer in the body. [...]

The concern, he and others say, is that taking this line of work many steps further could result in fully mirror-image bacteria that could reproduce. Such organisms would likely be able to infect and potentially harm a wide range of microbes, plants, and animals while resisting the molecules that enable predators to kill and digest existing microbes. "They are essentially unassailable to those enzymes," says John Glass, a co-author and synthetic biologist at the J. Craig Venter Institute. Animals' immune systems would also struggle to cope with mirror bacteria. They "would be invisible to the immune system until it was too late," says Timothy Hand, a co-author and immunologist at the University of Pittsburgh. The Policy Forum authors acknowledge it will be at least a decade before synthetic biologists will be capable of creating these life forms. Nevertheless, they recommend halting all research aimed at that goal and urge funding agencies not to support it.
"It's hard to overstate how severe these risks could be," says Ruslan Medzhitov, an immunologist at Yale University and one of the authors. "If mirror bacteria were to spread through infected animals and plants, much of the planet's many environments could be contaminated. ... Any exposure to contaminated dust or soil could be fatal."

Jack Szostak, a co-author and a 2019 Nobel Prize-winning chemist at the University of Chicago, adds: "The result could be catastrophic irreversible damage, perhaps far worse than any challenge we've previously encountered."

Leading Scientists Urge Ban On Developing 'Mirror-Image' Bacteria

Comments Filter:
  • by Baron_Yam ( 643147 ) on Thursday December 12, 2024 @10:35PM (#65009713)

    Chirality is uniform on Earth, as best we understand it, because one possible outcome just randomly got enough of a head start to out-compete the other.

    If the lefties and the righties are incompatible, that should affect both sides... if our immune systems can't see them, they shouldn't be able to compromise us anyway. If we're competing for some fundamental resource, there's more of us than them and they won't get far before dying out.

    Not that I'd risk an ecosystem on that, but in a nice BSL-4 lab? There's enough to learn to risk that.

    • by OrangeTide ( 124937 ) on Thursday December 12, 2024 @10:51PM (#65009727) Homepage Journal

      Makes sense. Let's go ahead and make cool shit, it won't Andromeda Strain us at all, nope.

      I guess some people still have faith in our systems and government that biosafety levels and other standards will still mean something before the end of the next administration.

      Image if biolabs were all managed like Tesla? And as unlikely and stupid as that may seem. All it might take is for someone like Tesla's CEO to be put in a position where he can define government policy. I know, just me being silly and paranoid and making up hypotheticals that could never possibly come about.

       

      • by quenda ( 644621 )

        Image if biolabs were all managed like Tesla? And as unlikely and stupid as that may seem.

        It would be like your comment. NOBDY would do that. Even the guy who takes big risks with rockets (who needs baffles?) is very worried over existential threats to mankind. One reason for the Mars colony is threats like this. Not just him, the culture among that group in Silicon valley many not care so much about individual people right now, because they prioritise the longterm survival of the species.

        AI is the biggest threat he talked about, followed by global warming, though he has been de-emphasising th

        • AI is the biggest threat he talked about, followed by global warming, though he has been de-emphasising the latter recently. It sound like mirror bacteria would make the list.

          And despite him seeing AI as the biggest threat, he's spending absolute stupid money on building it.

          Now while I personally think the AI danger is a bit overblown (at least the type we are using in LLMs) , it signals something rather worrying about the guy that he seems to go from "This shit could kill us all" to "... so lets do it!"

          • by RockDoctor ( 15477 ) on Friday December 13, 2024 @06:40AM (#65010229) Journal
            The threat he sees is that of AI taking over WITHOUT making him a profit in the process.
          • He's not really worried about any existential threats to mankind, those concerns are really about drumming up support for other issues he has a personal or usually vested interested in. Global warming was Telsa-driven self-interest, AI was the same for OpenAI, the light of consciousness in the universe being snuffed out and the need to become an interplanetary species was the same for SpaceX, worries about population decline were a sanitized version of Great Replacement theory before he was ready to come ou

          • AI is the biggest threat he talked about, followed by global warming, though he has been de-emphasising the latter recently. It sound like mirror bacteria would make the list.

            And despite him seeing AI as the biggest threat, he's spending absolute stupid money on building it.

            Now while I personally think the AI danger is a bit overblown (at least the type we are using in LLMs) , it signals something rather worrying about the guy that he seems to go from "This shit could kill us all" to "... so lets do it!"

            He's just egotistical enough to actually believe that only he is capable of making a "safe" AI. And arrogant enough to believe that he should be in charge of computer god.

        • Fan-boi alert!
        • by unrtst ( 777550 )

          AI is the biggest threat he talked about, followed by global warming, though he has been de-emphasising the latter recently. It sound like mirror bacteria would make the list.

          As sg_oneil[^1] noted, Musk is spending gobs of money on AI. He justifies it, at least in part, by saying it's such a threat that he has to make sure someone smart, like him, is managing it. I hope no one tells him about mirror bacteria, cause I'm pretty sure he'd want to be the forerunner in creating it out of fear that someone dumber than him would do it first.

          [^1] OMG is this the real MacGyver???

      • by dfghjk ( 711126 )

        Then the entire subject is moot anyway. If the problem is incompetence at the highest levels, the highest levels won't legislate a solution.

        Besides, billionaires already have a plan for this, AI. They don't need the vast majority of the population to survive anyway. It only matters if it threatens them.

    • by ceoyoyo ( 59147 )

      I'm not sure why they'd expect these to be dangerous. Any mirror bacteria are going to find themselves in a world where L-glucose doesn't exist, except for the small lab quantites that are synthesized and presumably used to feed them, and D-amino acids are very few and far between, except the occasional one that is already made and used by... bacteria.

      • by djinn6 ( 1868030 )

        Yeah. If I recall correctly, the immune system attacks anything it doesn't recognize with molecules like H2O2, which doesn't care about the chirality of the thing being attacked.

        Also bacteria has figured out how to eat plastic after it became prevalent in the environment. If mirror bacteria becomes common, it's only a matter of time before something figures out how to eat it.

      • by DarkOx ( 621550 )

        I am not a biologist but I would not make any assumptions, for the sake of betting. For the sake of avoiding calamities I'd assume if we experiment with this stuff only under the most tightly controlled conditions, to avoid environmental contamination; but that also applies to lots of other bio research.

        Just the run thru it though. Lack of L-glucose isn't a problem if the bacterium can produce its own via some other metabolic path and their are a lot of paths that lead to production of simple sugars.

        I don

        • by mysidia ( 191772 )

          I don't see why people or other organisms for that matter would have an immunity problem

          How does an immune system detect a foreign organism that doesn't look like an organism?

          a lot of how bacteria are attacked should still work chemically. They do things like cause cell membranes to break down

          My understanding is the cell membranes having the opposite protein chirality can potentially mean the cell membranes are not detected as membranes.
          Even if you have the means to break them down; you need a way to see th

    • but in a nice BSL-4 lab? There's enough to learn to risk that.

      Throw in poorly isolated ventiliation and high probability of exposing the local neighborhood and I would happily send you all my monies!

    • by 2TecTom ( 311314 )

      greed will be our undoing, these are corrupt, irresponsible and unethical people running the show

      what could possibly go wrong?

    • by sjames ( 1099 )

      Possibly. But consider, a bacterium that your immune system can't even see but it sees you as a big sack of sugar water and multiplies rampantly in the food enriched environment.

      Then what?

      • It wouldn't necessarily even be able to metabolize glucose. At least not the glucose that we commonly consume.

        • by RockDoctor ( 15477 ) on Friday December 13, 2024 @06:52AM (#65010239) Journal
          Have you heard of racemis[z]ation? Where an initially pure enantiomer (L or D, it doesn't matter) randomly rearranges until eventually you have an roughly equal mixture of L-enantiomer and D-enantiomer. That proceeds at various rates for different molecules.

          But also, most molecules above a small size have several biochemically interesting structures. If one is chiral, that doesn't mean all the others are too, and they are going to be as vulnerable to digestion as in any other molecule. Once you start splitting bits off a molecule like this, the odds of the remaining part getting racemised during the reaction rise rapidly.

          Ever wondered how white blood cells destroy "invaders" (molecules, entire bacteria or viruses, if they've received a surface tag from the host immune system)? They use strongly oxidising free radicles to chop up such molecules or whole organisms into small, inactive metabolisable components, regardless of chirality.

          Yes, chirality would be a barrier to growth for such an organism, but not an impregnable one.

        • Even if this is correct (another post raises some good points), there'd be enormous evolutionary pressure for those bacteria to figure out how to consume glucose. Bacteria being bacteria, I expect their population can evolve to eat glucose faster than my immune system can evolve to eat them.
        • by sjames ( 1099 )
          The ones that can't are not the ones that escape the lab. The ones that mutate so that they can are the concerning ones.
      • by locofungus ( 179280 ) on Friday December 13, 2024 @04:09AM (#65010081)

        While it's nice and scary, I doubt that this is a realistic problem.

        Far more likely is something that can reproduce in seawater and produces a waste product that turns out to be highly toxic to some critical life and is also stable - in human terms think toxicity of botulinum without the degradation in the presence of oxygen.

        Imagine, for example, something that wipes out all phytoplankton in a decade.

        The scary part about mirror molecules is that they're sufficiently similar to have a significant chance of interacting with existing biological reactions but sufficiently different that those reactions may not be able to complete - and this is one of the things that is exploited by the most toxic substances - to bind to some critical site and block an essential reaction.

        The most likely scenario is that chiral life will not be able to reproduce outside of a laboratory, it will be dependent on some critical chiral resource that isn't available in nature, but evolution is very good at taking advantage of opportunities and that one in a million chance that the mirror life finds some existing resource to exploit and then to reproduce without limit cannot be sanely ignored.

        • Imagine, for example, something that wipes out all phytoplankton in a decade.

          Over long enough time frames, I fully expect this to happen. Probably in less than a thousand years unless we wipe out all of civilization first. :(

    • That is not how it works.
      A bacteria infects you, it just eats stuff it wants to eat, inside of your body.
      Then it shits out the stuff that is its waste.

      You do not die to a bacteria like bubonic plague or salmonella because the bacteria is killing you. You die to the poisons they produce either as defense or as byproduct of their "shit".

      if our immune systems can't see them, they shouldn't be able to compromise us anyway.
      It does see them. But the antibody cocktail of the first response, does not bind to any of the surface structures of the target.

      So: as long as you have anything in your body a mirror image bacteria can eat, e.g. sugar, starch, and so on: it will shit you full with poison that kills you ... quick or slow.

      • Some bacteria will actually consume your cells. Pretty sure staph and strep can do that.

        • Most eukaryote cells (you, bananas, everything in between) are a lot larger then bacteria - typically by a factor of about 10 in length, and a thousand in volume. Which matters.

          Most bacteria that "destroy" [eukaryote] cells do so by attaching to the membrane ; breaching that, then engulfing some of what falls out. Kind of like a kitten eating her beloved, now dead, "granny" owner - they go in through the weakest point, then eat what falls out.

          Membrane molecules as a whole may be chiral or not - but since

      • if our immune systems can't see them, they shouldn't be able to compromise us anyway.
        It does see them. But the antibody cocktail of the first response, does not bind to any of the surface structures of the target.

        Why wouldn't the adoptive immune see them? It sees almost everything except what's been winnowed out of the fleet as "self." Autoimmune diseases come from errors in that.

        There's also the primitive innate immune system which doesn't do that sort of recognition.

    • Didn't they say those Martian fossils seemed to be mirror-image?

      But yeah, I was going to make the same point, that if Earth life can't consume mirror chemicals then neither can they consume ours.. A few really basic chemicals would be without chirality, but only a few.

      • Didn't they say those Martian fossils seemed to be mirror-image?

        Nobody I saw did, but I didn't trawl the depths of the Internet, just read the Science and Nature articles. I had personal subscriptions to one or the other for several years on either side of the relevant time.

        Molecular chirality does not necessarily reflect in macroscopic structure. If you have a few billion chiral molecules, selected for one chirality, and arranged into a crystal, then you can get macroscopically chiral crystals. This also

    • by clambake ( 37702 )

      > if our immune systems can't see them, they shouldn't be able to compromise us anyway.

      This is insanely wrong. They could very easily produce deadly toxins, like many bacteria do. Those toxins don't necessarily require any particular chirality to be extremely deadly.

    • by Ormy ( 1430821 )

      Not that I'd risk an ecosystem on that, but in a nice BSL-4 lab? There's enough to learn to risk that.

      Agreed. Especially since their opposite chirality only protects from attack by biological methods, all the chemical methods of killing bacteria will work just fine. E.g. antiseptics that destroy bacterial cell membranes by denaturing proteins will work equally well on these mirror-bacteria as they do on normal bacteria. Also the hydrochloric acid in your stomach.

    • by e3m4n ( 947977 )

      Maybe a space lab with zero chance of escaping. I suppose any time we bring back rocks or soil samples from a foreign planet we risk the remote chance of a similar exposure. We cannot assume that a microbe evolved the same way they did on earth.

    • by sinij ( 911942 )

      if our immune systems can't see them, they shouldn't be able to compromise us anyway.

      Citation required.

    • If the lefties and the righties are incompatible, that should affect both sides... if our immune systems can't see them, they shouldn't be able to compromise us anyway. If we're competing for some fundamental resource, there's more of us than them and they won't get far before dying out.

      What you are describing is akin to a world full of chocolate chip cookie people after cookie monster lands on it and starts eating and fucking.

    • by flink ( 18449 )

      This is just completely false. Many innocuous or beneficial compounds have isomers with the opposite chirality which are toxic. A bacteria that produces a totally harmless waste product when in the D- isomer, could be deadly as an L- isomer. Worse, having all of its marker proteins reversed could render it invisible to the immune system or reduce the effectiveness of all the various chemical weapons the immune system employs. An organism with mirror chirality might not even be trying to attack us, but c

    • Not that I'd risk an ecosystem on that, but in a nice BSL-4 lab? There's enough to learn to risk that.

      Didn't you hear how returned asteroid rocks kept in the maximum containment already have bacterial contamination?

    • Chirality is uniform on Earth, as best we understand it, because one possible outcome just randomly got enough of a head start to out-compete the other.

      If the lefties and the righties are incompatible, that should affect both sides... if our immune systems can't see them, they shouldn't be able to compromise us anyway. If we're competing for some fundamental resource, there's more of us than them and they won't get far before dying out.

      Not that I'd risk an ecosystem on that, but in a nice BSL-4 lab? There's enough to learn to risk that.

      Remember the Great Oxidation Event [wikipedia.org]? It basically happened because an unstable ecosystem changed the planet's environment to the extent that it wiped out a big fraction of living organisms. It took billions of years for the microbial ecosystem to stabilize enough to make multicellular life possible. I think that's the worry with mirror image life, not that it will infect us or even compete with us, but that it's a single organism, or handful or organisms with zero predators.

      If it gets out it could seriously

    • Not sure what type of lab this happened.

      https://www.newsweek.com/deadl... [newsweek.com]

      If it wasnt BSL-4, should that lab even be having dangerous virus in the first place? If it was BSL-4, I guess not all BSL-4 labs are the same.

  • by crow ( 16139 ) on Thursday December 12, 2024 @10:47PM (#65009723) Homepage Journal

    Isn't Mad Cow Disease related to this? As I recall, it's a prion disease, where. a protein is folded the "wrong" way, but when that protein encounters the version folded the normal way, the other one swaps to the "wrong" way, too. And then the protein doesn't do what it normally does.

    It's a folding issue, which may be different from what is discussed here, but it's certainly along the same lines.

    • Re:Mad Cow Disease (Score:5, Informative)

      by ceoyoyo ( 59147 ) on Thursday December 12, 2024 @11:59PM (#65009793)

      Chirality isn't about proteins that are folded the wrong way. The actual molecule is different. You can metabolize D-glucose just fine, for example, but not L-glucose, the mirror image.

      The key thing about prions is that they're "infectious." When the prion comes in contact with a normally folded version it tends to make it misfold into the prion type. Stereoisomers don't do that at all.

      • You can metabolize D-glucose just fine, for example, but not L-glucose, the mirror image.

        But a solution of D-glucose will spontaneously (don't ask me the reaction rate ; I'm a geologist, not a chemist!) flip some molecules from D- to L- . I think the rate is strongly affected by solution pH - which means (really stretching my chemistry here!) an electrophilic attack on a double-bond?

        • I'm not a chemist:

          But a solution of D-glucose will spontaneously (don't ask me the reaction rate ; I'm a geologist, not a chemist!) flip some molecules from D- to L- . I think the rate is strongly affected by solution pH - which means (really stretching my chemistry here!) an electrophilic attack on a double-bond?

          This feels "surprising". Are you sure you're not confusing the transition between \alpha and \beta forms in aqueous solution? I believe that the three forms are (approximately) stable as solids bu

  • by JustAnotherOldGuy ( 4145623 ) on Thursday December 12, 2024 @10:52PM (#65009729) Journal

    Technology may finally permit History to have an end.

  • they recommend halting all research aimed at that goal and urge funding agencies not to support it

    So essentially, the need to create a bill named "No FAFO Biology Policy" and approve it.

  • So what if we do develop this ... we'd be even a stronger Nation than now

    https://www.youtube.com/watch?... [youtube.com]

  • by vbdasc ( 146051 ) on Friday December 13, 2024 @12:07AM (#65009807)

    If it can be technically done, it will be done by someone, bans or not. If humanity goes extinct, it will be it's fault for its inability to cooperate at this level of technology development.

    • by Tablizer ( 95088 )

      Bio-weapons, mad AI, Trumps, we are focking dooomed!

    • by Jeremi ( 14640 )

      If it can be technically done, it will be done by someone, bans or not.

      Counterexample: if you're old enough, you might recall the hole in the ozone, layer caused by CFCs... then in 1998 world governments, led by the US, agreed on the Montreal Protocol which banned the production of CFCs. Since then, CFC levels in the atmosphere have decreased, and the ozone layer is expected to fully recover by the middle of this century.

      Technically, CFC production can be done today -- it isn't rocket science -- but nevertheless, it isn't being done (at least, not at any significant scale).

      • Your example with the ozone layer isn't a counter-example. At best, it's an example that people can still cooperate when it iare sn't too inconvenient to do so (it's worse with the global warming). But weapons of mass destruction, killer AIs etc. are a different thing. When they're viable, someone creates them, be it a mad dictator, Dr. Evil, ISIS etc.

      • the hole in the ozone, layer caused by CFCs.

        It's not the most wonderful argument, but not for @vbdasc's reasons.

        The Montreal protocol did not ban the production of CFCs, it strongly restricted their production in the "first world", and discouraged it's production in the "third world", but permitted it, because volumes were low, and the production plants for alternatives were not available.

        Unfortunately, since then China (in particular ; India may be on the same trajectory) has moved from (arguably) "thir

      • Most(all?) industries have switched from CFCs to other stuff.

        If you don't have a customer for CFCs, you going to burn money making them. If you are making them for "fun", I guess there is a bigger problem.

    • Step 1. Write a book named "please do not create the torment nexus"
      Step 2. Write a blog / article explaining that no, we really should not build a Torment nexus did you not get the point?"
      Step 3. Corporation inevitably builds the Torment Nexus
      Step 4. Realize we live in the darkest timeline - wtf?
      Step 4. Apologize to the world for inspiring the Torment Nexus

    • "Some humans would do anything to see if it was possible to do it. If you put a large switch in some cave somewhere, with a sign on it saying 'End-of-the-World Switch. PLEASE DO NOT TOUCH', the paint wouldn't even have time to dry."

  • There's no reason to assume that a mirror image bacteria would be invisible to the immune system. That's not a worry. I don't know that a few engineered bacteria would survive in the wild since there would be few nutrients for it. And I kind of doubt that we're anywhere near being able to build one of these beast. Much ado about nothing. Move on.
    • by quenda ( 644621 )

      Are you a biochemist? I'm not, but google tells me that bacteria only need nitrogen etc, not proteins or even specific amino acids like we do.

      • by methano ( 519830 )
        I'm a 70 yo organic chemist. I think this recent fear mongering about mirror life is a bunch of hooey, stirred up by people who want something else to worry about besides the fact that we've just learned that half the American population is beyond stupid.
      • but google tells me that bacteria only need nitrogen etc

        If google is telling you that, then either it's misleading, or you're reading it wrong.

        Some bacteria can make this amino acid, or that "vitamin", which humans (or bananas, or mosquitos, or some particular eukaryote) can't make. So? Eukaryotes have essentially one biochemistry ; bacteria have an uncertain, but large, number of biochemistries, with different capabilities for each one (or several).

        You mention "fixing" nitrogen ("di-nitrogen", N2, from t

    • There's no reason to assume that a mirror image bacteria would be invisible to the immune system.

      I think you're the first person to make this point - which I agree with.

      So, a "mirror image" bacterium would have amino acids in it's coat proteins that have different shapes to those of the immune system attacking it. The random-shape-generator in the immune system will (eventually) find a shape that does match the target "mirror-bacterium" (and coincidentally does not match any "self" antigens ; immune syste

  • The main risk right now is from the gain of function research.
    You don't have to be convinced of the covid-lab leak thesis in order to come to that conclusion , even before covid.
    The awful thing is that once people manage to slap the 'conspiracy thinking ' label on is everybody's thinking just shuts down. Not only about this instance but about the general risk.

    Seriously, not only are there a lot of conspiracies going on at any time, how is a lab leak even a conspiracy? Conspiracy to cover it up , sure. But

  • Here I was think I had enough to worry about and they come up with this crap. I really must get out of the habit of getting out of bed in the morning, it never seems to lead to anything good these days...
  • Vast numbers of prescription drugs have right and left hand molecules. Consumers get prescriptions with mostly the preferred variation, but also mirror image contaminates. This is not so funny, as SE Asia and others find ways into the livestock foodchain, begging a resistant outbreak. Guess what - fish, chickens and prawns get antibiotics, possibly more - given why assay animal biotics. Now if they combine with something nasty in the soil, then .....
  • To find countermeasures we must first create these pathogens and find out how to make them as virulent as possible.

    Then when they escape, blame raccoon dogs.

  • The announcement now has told every enemy of modern civilization what to study to end the world. Or something like that. Curious have they found these mirror drugs in effluent water? And what mechanisms exist for such microorganisms to naturally die out? It sounds like if they are very low-level organisms they might just be out-competed but if they are human-attacking organisms there is no time for that to happen? Not sure (and not sure I want to know) why a virus like Covid isn't a lot worse than that. The

  • We have two elementary ways to perceive our interactions with 'alien chemicals'
    - the War of the Worlds way: When the Spanish landed in South America they brought diseases the people in South America had no defense against and they all died.
    - The separate worlds way: two specialized mechanisms exist next to each other , they have not adapted to each other and therefore they can barely interact and they mostly act as if the other does not exist.

    with mirror chemistry we know a lot of stuff won't fit so the sep

    • by GuB-42 ( 2483988 )

      For the "War of the Words way", the difference here is that the plagues that affected the South Americans are very well adapted to infecting humans, immunized or not. It is absolutely not the case for mirror-image bacteria, who would need mirror-image humans to infect.

      So yeah, I would go with the "separate worlds" too, or more likely, the "aliens stand no chance and die world".

  • "gray goo" is a catastrophic scenario where we build self-replicating machines, nanomachines in particular, and we lose control.

    Scary in theory, but most knowledgeable people object that making self-replicating machines is hard enough as it is, even in a perfectly controlled environment, that there is essentially no chance that such a machine would be viable out of the lab, especially going against life that had billions of years to evolve.

    I guess that viable mirror-image bacteria are easier to make than na

  • Seems like this is just like Greg Bear's 1985 novel "Blood Music" and what happens when something gets out of the lab. https://en.wikipedia.org/wiki/... [wikipedia.org].

A complex system that works is invariably found to have evolved from a simple system that works.

Working...