{"id":15990,"date":"2022-08-03T13:00:55","date_gmt":"2022-08-03T11:00:55","guid":{"rendered":"https:\/\/www.sciencefocus.com\/?p=125245"},"modified":"2022-08-03T13:16:09","modified_gmt":"2022-08-03T11:16:09","slug":"what-a-mysterious-green-sludge-discovered-in-lava-caves-tells-us-about-life-on-other-planets","status":"publish","type":"rss_feed","link":"https:\/\/c01.purpledshub.com\/bbcsciencefocus\/rss_feed\/what-a-mysterious-green-sludge-discovered-in-lava-caves-tells-us-about-life-on-other-planets\/","title":{"rendered":"What a mysterious green sludge discovered in lava caves tells us about life on other planets"},"content":{"rendered":"

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By Sara Rigby\n \t\t<\/p>

Published: Wednesday, 03 August 2022 at 12:00 am<\/p>

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Deep within the lava caves of Hawaii, microbial life thrives. In fact, a recent study has found that the life teeming within the caves is made up almost entirely of unknown species<\/a>.<\/p>\n

More surprisingly, the researchers found that the microbial life was structured into complex networks of species that relied on each other. Within these networks were \u2018hub species\u2019, with so many links to other species that if they were removed, it could cause ecological collapse.<\/p>\n

We spoke to Dr Rebecca Prescott<\/a> and Dr Stuart Donachie<\/a>, microbiologists at the University of Hawaii at M\u0101noa and authors of the study.<\/p>\n

How did you search for life in these lava caves?<\/h4>\n

Dr Rebecca Prescott:<\/strong> We had 70 samples of microbial mats [layers of microbes that live on surfaces] that we looked at from a variety of volcanic environments of different ages. The environments included lava tubes, geothermal caves and steam vents.<\/p>\n

In order to identify the microbes, we looked at a gene called the \u201816S rRNA gene\u2019. It\u2019s like a little tag that helps us with identification. We also looked at what microbes were \u2018hanging out\u2019 together, to try to better understand the structure of these communities.<\/p>\n

Tell us more about this technique.<\/h4>\n

Dr Stuart Donachie:<\/strong> Prior to 1986, microbiologists could only identify microbes that they\u2019d cultured in the lab. Everything we knew about microbial diversity \u2013 meaning how many species there are \u2013 was based only on what we could grow in Petri dishes. That gave us a rather narrow view, but it was the best we could do at that time.<\/p>\n

In 1986, there was a method developed that involved sequencing [the 16S rRNA gene]. This method based on extracting as much DNA as possible from the environmental sample, and then making copies of this particular gene. Once this method was applied in the environment, we detected bacteria that had never been seen before.<\/p>\n

RP:<\/strong> There are lots of microbes in the environment that have never been cultivated. The majority of them haven\u2019t been. We saw a lot of microbial groups [in the volcanic samples] that are what we call \u2018hub species\u2019, meaning that they have a lot of connections to other species of bacteria in these networks. If you were to remove them, you might see a lot of those connections collapse. So they may have important ecological roles.<\/p>\n

What sort of things do these hub microbes do?<\/h4>\n

RP:<\/strong> I can only speculate here. I want to stress that we don\u2019t know what their function is. But one example of a hub species would be the Chloroflexi bacteria that we found in the volcanic environments. Some Chloroflexi can photosynthesise at low light levels. They may be able to take carbon into the system. Other organisms around them may not have that ability to photosynthesise in really low light.<\/p>\n

SD:<\/strong> Anywhere you get these photosynthesising organisms [such as Chloroflexi], they take inorganic carbon and they make organic molecules from that. But they\u2019re kind of like leaky cells \u2013 they excrete other biological molecules into the environment. They also die. Their cells break down and it releases the contents of the cells into the environment, and that allows other organisms to grow, which need pre-formed organic molecules.<\/p>\n

RP:<\/strong> I study \u2018quorum sensing\u2019, which is bacteria talking to each other through chemicals. When they do this, they can respond to something in the environment as a group.<\/p>\n

Part of the reason we wanted to understand these network structures is because we see really high levels of quorum-sensing genes in a lot of caves, and I don\u2019t have a good explanation as to why you would see that. So that\u2019s another possibility for why you may get a particular organism showing up as a hub species in a network \u2013 it could be that it\u2019s doing something and then is communicating with others.<\/p>\n

Could this tell us more about microbes in other extreme environments?<\/h4>\n

SD:<\/strong> I don\u2019t know that we necessarily addressed this in this study, but as a personal observation, [research like this demonstrates] the importance of water. I went into probably 20 caves in the K\u012blauea caldera between 2006 and 2009. And some of them are completely dry and a regular temperature. It was a challenge to identify anything biological, except for the plant roots coming through the ceiling.<\/p>\n

But in others, the cave was hot and extremely humid. Relative humidity was about, I think, 102 per cent. It\u2019s like being in a sauna. There was rainwater from the ground above dripping through the ceiling, then flowing over the walls of the cave and dripping onto the floor. The floor was hot \u2013 we put a temperature probe into the ground and it was something like 90\u00b0C a couple of inches down.<\/p>\n

The water that was coming from the ceiling was dripping onto the floor and being converted into steam. So you get this kind of circulation of rainwater becoming groundwater, and then being converted into steam. And that\u2019s where we saw the richest, thick, green microbial mats, which kind of illustrates the importance of water.<\/p>\n

That\u2019s why we always say where there\u2019s water, there\u2019s life. Life, at least as we know it, needs water. Hence we\u2019re looking for liquid water on other planets or any other body, because that\u2019s the first thing we know of that\u2019s needed for life.<\/p>\n

Read more about microbial life:<\/strong><\/p>\n