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Sub-zero heroes: extremophiles call salty Antarctic lakes home

Imagine a lake so salty its water exists in a liquid state at -20 °C – then picture something thriving in that seemingly lethal environment. Such an organism exists; several of them, in fact. In a paper…

Even with water temperatures down to -20°C, Deep Lake is home to a surprising amount of life (and not just our research camp). Rick Cavicchioli

Imagine a lake so salty its water exists in a liquid state at -20 °C – then picture something thriving in that seemingly lethal environment.

Such an organism exists; several of them, in fact. In a paper published in the Proceedings of the National Academy of Sciences today, along with colleagues from UNSW and the US, I describe those microbes – dubbed “extremophiles” – which live in the hostile depths of an Antarctic lake.

As their name suggests, extremophiles are organisms that thrive in environments deadly to other living things. Examples include radioresistant extremophiles which need nuclear waste to survive; some (thermoacidophiles) prefer to reside in near-boiling acidic water.

The colours of the Grand Prismatic Spring in Yellowstone National Park are the result of pigmented extremophile bacteria. Achint Thomas

Still others call the saltiest and least life-producing lake in the world – Deep Lake in Antarctica – their home.

Located around 5km from Davis Station, Deep Lake was formed about 3,500 years ago when the Antarctic continent rose, isolating a section of ocean. The water in the 36m deep lake is now so salty it remains in liquid form down to –20 °C and, unsurprisingly, almost nothing is able to grow in it.

What does grow, though, is fascinating.

We took water samples from the lake at depths of five, 13, 24 and 36 metres. We studied the entire genetic sequence, or genome, of the microbes living there, to work out how they had evolved to cope with the extremely harsh conditions.

The halophilic (Greek for “salt-loving”) extremophiles in Deep Lake belong to a group of microbes called haloarchaea. Due to much higher rates of gene-swapping – or promiscuity – than normally observed in the natural world, many species in Deep Lake are able to benefit from the genes of others.

What is also remarkable is that in addition to all the promiscuous gene swapping, the dominant members of the community retain their own identity as a species, and coexist with others, exploiting different niches without impinging on each other.

Some microbes consume proteins in the water. Others consume sugars like glycerol, a by-product of algae living in the upper waters of the lake. The most prolific extremophile we found in Deep Lake – tADL – was one of the latter, comprising about 44% of the total cell community.

Deep Lake, Antarctica – home of halophilic microorganisms. Mark Milnes

Industry and astrobiology

It is estimated the haloarchaea grow very slowly in the lake, with only about six generations produced a year.

Enzymes from cold-adapted microbes could have significant industrial value. Their high activity in cold temperatures could provide reduced energy costs for processes that would otherwise require heating (such as cleaning) or which must be carried out at cold temperatures (such as food production or removing pollutants from cold, contaminated sites).

Those enzymes will be especially useful for transforming contaminated sites with particularly high levels of petroleum-based products.

Haloarchaea cells. NASA

Our findings that the haloarchaea in Deep Lake have the remarkable ability to grow under such cold and salty conditions provide thought-provoking insight for astrobiology studies – perhaps extraterrestrial life will exist in salty veins within ice present on planets and moons within our solar system (such as Jupiter’s icy moon Europa).

As a means of searching for extraterrestrial life, the enzymes from these cold-adapted haloarchaea may also be valuable for use in biosensors to assess whether biological reactions are taking place on other worlds.

Microbe cycles

In October this year, we will set off again for our third Antarctic expedition – this one lasting more than 12 months.

Building on knowledge gained from previous expeditions (one which lasted six weeks in 2006 and another of three months in 2008), the purpose of this trip is to monitor ecosystem stability in model marine-derived Antarctic lake and near-shore systems; in essence, addressing the question of what microorganisms do season by season, year after year in the frigid Antarctic wilderness.

Taking water samples from the middle of Deep Lake, December 2008. The boat was tethered to shore by a kilometre length of rope. Supplied

Our aim is to determine how microbial communities change throughout a complete annual cycle in three climate-sensitive Antarctic lakes – Ace Lake, Organic Lake and Deep Lake – and in a near-shore marine location.

Our group’s research to date reveals that Antarctic microbial communities are very delicate, with indications that environmental perturbation, including climate change, may prevent such communities from recovering, thereby altering the lake biogeochemistry forever.

Establishing what the microorganisms do in different seasons will reveal which microbial processes change, and how environmental perturbation will impact on normal ecological cycles in the Antarctic.

This essential evidence-based knowledge will form the underpinnings for evaluating the effects of climate change on sensitive ecosystems in the Antarctic.

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20 Comments sorted by

  1. Russell Y

    Financial planner

    What a fascinating and breath taking place. I have read about the dry valleys and some of the volcanic regions of the southern continent but this feature is something else. The organisms investigated really shows the incredible variety of life on this planet. Well done to The Conversation for bringing this to the mainstream. I really wish that Michelle Gratten could appreciate and comment from the science for the importance of dealing with global warming so that the above diversity continues on.

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    1. Rick Cavicchioli

      Professor of Biotechnology and Biomolecular Sciences at UNSW Australia

      In reply to Russell Y

      Russel yes there is a lot more that can be done and should be done to alleviate anthropogenic climate change. See 3rd para comment to Paul Prociv.

      One of the things we are striving to learn is just how diverse the biota is across the vast expanse of Antarctica. DNA sequencing based technologies are very cost effective for providing data about which organisms are present, so an important focus is obtaining samples from wide ranging locations and using ‘omic’ approaches to characterise the communities.

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  2. Paul Prociv

    ex medical academic; botanical engineer at University of Queensland

    Thanks for sharing this amazing piece of research with us - fascinating and extremely (excuse pun) important work. But I must take slight issue with your conclusion, about how fragile these little beasts are, and how climate change might stuff them up.
    Firstly, they managed to survive extreme climate change in the first place, to get where they are, and secondly, as you say yourself: "Due to much higher rates of gene-swapping – or promiscuity – than normally observed in the natural world, many species in Deep Lake are able to benefit from the genes of others." Doesn't his mean that they are perfectly set up to adapt to whatever conditions nature might throw at them, far better than us slow changers?

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    1. Rick Cavicchioli

      Professor of Biotechnology and Biomolecular Sciences at UNSW Australia

      In reply to Paul Prociv

      Paul you are right that microbes will indeed outlive humans, despite the variety of negative impacts we are making to the global environment. The study found that the communities in Deep Lake are distinct from those in temperate or tropical lakes (such as those in outback Australia, or the Dead Sea). So the unique environmental conditions in Antarctica have selected for a certain type of community. Change the environmental conditions (e.g. as a result of global warming, contamination of the lake…

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    2. Dianna Arthur

      Environmentalist

      In reply to Rick Cavicchioli

      Terrific article and thanks for the explanation of the importance of the ecosystem in which these otherwise very adaptable microbes flourish.

      When I read:

      "Due to much higher rates of gene-swapping – or promiscuity – than normally observed in the natural world, many species in Deep Lake are able to benefit from the genes of others.

      What is also remarkable is that in addition to all the promiscuous gene swapping, the dominant members of the community retain their own identity as a species, and coexist with others, exploiting different niches without impinging on each other."

      I couldn't help but wonder if such abilities would be anathema to those of the far right. Apologies for political reference, can't help myself ATM. Imagine a world where we all cooperated with each other, without being forced to follow the dogma of others, thus maintaining our integrity and sharing at the same time.

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    3. Rick Cavicchioli

      Professor of Biotechnology and Biomolecular Sciences at UNSW Australia

      In reply to Dianna Arthur

      Dianna it is interesting that microbial communities evolve through selection that involves interactions with others that achieves a balance of competitive individuals and sub-populations that coexist and ultimately produce a healthy ecosystem. They are also naturally dynamic and responsive to ecosystem change. Humans of course have the great advantage of being able to use their intellect to choose to make changes that can greatly benefit themselves and the broader community. Clearly when smart and informed groups (like Beyond Zero Emissions) come up with sensible plans to utilize existing technologies to be able to greatly improve our environment, it makes all the sense in the world to choose to do just that.

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  3. Robert Corran

    IT Professional

    Thanks for a fascinating article. I find it curious that everywhere we look we find some form of life. Life has evolved to fill every niche. How could one believe that our planet is the only one that harbours life? It may not look like us or have a similar chemistry to terrestrial life but it must be out there.

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    1. Rick Cavicchioli

      Professor of Biotechnology and Biomolecular Sciences at UNSW Australia

      In reply to Robert Corran

      Robert what you say makes intuitive sense. The discovery that microorganisms can and do colonize environments that are well outside of the hospitable Earthly niches that humans live in, certainly expands our horizons in the search for extraterrestrial life. Methanogens (archaea that grow by producing methane) are great examples of life forms that have species that can grow at temperatures below 0C, to others that can grow at 122C. They can also grow by consuming inorganic compounds (hydrogen, carbon dioxide, ammonia) to produce organic matter. They do not use oxygen, and some do not require organic matter to grow, and some can also tolerate huge levels of radiation. Providing water is available, these types of organisms would love to colonize environments beyond Earth – Mars is a good example.

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    2. Rick Cavicchioli

      Professor of Biotechnology and Biomolecular Sciences at UNSW Australia

      In reply to Dianna Arthur

      Dianna, "these types of organisms would likely be capable of colonizing these environments" is really my point.

      But yes, the notion of terraforming vs being very careful to not contaminate extraterrestrial environments, provides for good discussion.

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    3. Dianna Arthur

      Environmentalist

      In reply to Rick Cavicchioli

      Rick

      I already got your point. I thought the entire point of the article was that we can expect to find living organisms in environments that are hostile to humans, given discoveries such the the microbes in Antarctica.

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  4. Malcolm A. Seguel Rios

    logged in via Facebook

    What a great piece, so interesting. Is it worth while looking into the micro/organisms that come to contact with the Lake to see what initialized the microbial growth/cycle and recreate it in a lab environment? ie; Parasites off Seals, Penguins or Birds.. Keep up the great work!

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    1. Rick Cavicchioli

      Professor of Biotechnology and Biomolecular Sciences at UNSW Australia

      In reply to Malcolm A. Seguel Rios

      Malcolm one of the nice things about the haloarchaea is that we can grow many of them in the lab, which is often not the case for environmental microorganisms – so in principle, the type of experiments you describe would be possible. With regards to what seeded the lake in the first place, it is an interesting question. As stated, the lake is marine-derived. Haloarchaea have an obligate requirement for very high salt, so the bulk of the marine environment will not suit. They can grow on salted fish…

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  5. Manasha Savi

    logged in via Facebook

    This is really interesting. May I ask how can the dominant members of this microbe community maintain their own identity even with a lot of gene swapping going on? I would be glad if anyone could answer :) Thank you in advance

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    1. Rick Cavicchioli

      Professor of Biotechnology and Biomolecular Sciences at UNSW Australia

      In reply to Manasha Savi

      Manasha, the dominant members each have specific characteristics (e.g. metabolism favouring different growth substrates) that means they don't compete for exactly the same resources. This enables them to coexist through ecological mechanisms of niche adaptation. This is an important finding described in the paper. I hope this helps.

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    2. Dianna Arthur

      Environmentalist

      In reply to Rick Cavicchioli

      I should have clarified my question, (thanks for fast reply BTW).

      The introduction of similar microbes - say from another salty, cold environment? Could not these be lab tests, recreating the conditions in which the microbes survive? In fact, are there distinct communities, separate from each other but which vary by a gene or two?

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    3. Rick Cavicchioli

      Professor of Biotechnology and Biomolecular Sciences at UNSW Australia

      In reply to Dianna Arthur

      Dianna, if a similar but geographically isolated lake existed where a different community of haloarchaea had evolved, then yes conceivably these haloarchaea could be competitive in Deep Lake and therefore if they were introduced they could change the community in Deep Lake. I am heading back to Antarctica in a few weeks and part of the expedition will be to look at other hypersaline lakes to determine what communities exist. But in the Vestfold Hills where I will be going I don't think the other systems will be as salty as Deep Lake. One lake about 15 km away from Deep Lake, called Organic Lake, has salinity about 6x marine, but this lake is not salty enough to sustain haloarchaea. I hope this addresses your question?

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    4. Dianna Arthur

      Environmentalist

      In reply to Rick Cavicchioli

      Thanks, Rick.

      That does help.

      Wish I was going with - one of those dreams unlikely to be for-filled.

      I find this type of study fascinating - from the heat vents in deep sea, through to cold 'n salty, we find life.

      Hoping you discover many interesting life-forms - AND write about them here.

      Cheers

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