How do these little beasties detect light anyway?
Photoreceptors and optogenetics<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yNTU5MjgyNS9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTYzOTI2MDY1NH0.-6sF7JMwIGoHA7uaHQbyYuNMPDNyC6MksR07LTRZHOw/img.jpg?width=980" id="faa85" class="rm-shortcode" data-rm-shortcode-id="5cd3e532357212eeb97bf505462cff74" data-rm-shortcode-name="rebelmouse-image" data-width="1440" data-height="1080" />
Credit: ktsdesign/Adobe Stock<p>Aside from being fascinating in their own right, these little "light switches" are likely to be of great interest to people working in <a href="https://kids.frontiersin.org/article/10.3389/frym.2017.00051" target="_blank">optogenetics</a>, a <a href="https://www.scientifica.uk.com/learning-zone/optogenetics-shedding-light-on-the-brains-secrets" target="_blank">transformative</a> area of scientific research.</p><p>This combination of optical technologies and genetics is giving researchers new insights into the workings of the brain, allowing them to, for example, turn on and off <a href="https://www.sciencedaily.com/releases/2017/11/171113123803.htm" target="_blank">single neurons</a> as they explore the brain's myriad pathways and interactions. Optogenetics also holds promise for <a href="https://www.sciencedaily.com/releases/2016/04/160420111154.htm" target="_blank" rel="noopener noreferrer">better management of pain</a>, and has cast new light on <a href="https://www.sciencedaily.com/releases/2018/01/180117131149.htm" target="_blank">brain motor decision-making</a>.</p><p>These new-found, naturally occurring photoreceptors may substitute for, or complement, human-made photoreceptors currently used in optogenetics. It's hoped that these newcomers will prove more sensitive and better equipped to respond to particular light wavelengths. Possibly because water filters out red light—the reason the ocean looks blue—the new photoreceptors are sensitive to blue and green wavelengths of light.</p><p>"This work dramatically expanded the number of photoreceptors — the different kinds of those on-off switches — that we know of," offers Armbrust.</p>
Finding the new photoreceptors<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yNTU5MjgzMC9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTYyNzkwOTI0M30.S0S0EoCXuO8qi7Q0lytHQhC8ZEK_IAmo3mrMhNygnho/img.jpg?width=980" id="55a8c" class="rm-shortcode" data-rm-shortcode-id="47717b9aba62379f2cefe87fb2fdda76" data-rm-shortcode-name="rebelmouse-image" data-width="640" data-height="480" />
Credit: Dror Shitrit/Simons Collaboration on Ocean Processes and Ecology/University of Washington<p>The researchers identified the previously undiscovered groups of photoreceptors by analyzing RNA they'd filtered from seawater samples taken far from shore. The samples were collected every four hours over the course of four days from the Northern Pacific Ocean near Hawaii. One set of samples was collected from currents running about 15 meters beneath the surface. A second set sampled deeper down, gathering water from between 120 and 150 meters, in the "<a href="https://www.whoi.edu/know-your-ocean/ocean-topics/ocean-life/ocean-twilight-zone/" target="_blank">twilight zone</a>" where organisms get by with little sunlight.</p><p>Filtering the samples produced protists—single-celled organisms with a nucleus—measuring from 200 nanometers to one tenth of a millimeter across. Among these were light-activated algae as well as simple plankton that derive their energy from the organisms they consume.</p>
Under-appreciated, tiny drivers of sea health<p>The new photoreceptors help fill in at least one of the blanks in our knowledge of the countless floating communities of microscopic creatures in our seas, communities that have a far greater impact on our planet than many people realize.</p><p>Says Coesel, "Just like rainforests generate oxygen and take up carbon dioxide, ocean organisms do the same thing in the world's oceans. People probably don't realize this, but these unicellular organisms are about as important as rainforests for our planet's functioning."</p>
A new study suggests that maintaining gut health to avoid diabetes may be little simpler than previously believed.
- Four out of trillions of gut microbes have been identified as being especially important for health.
- The microbes may play a role in obesity that can result in type 2 diabetes.
- Understanding the microbes' roles may lead to new probiotics for preventing and treating type 2 diabetes.
Type 2 diabetes<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yNTI2MTQ5OC9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTY3NzQzNjgwNn0.Gq5CqC2OPB6pa7I4K1v1PicEcG5gskXKb-kh6FEUfPU/img.jpg?width=980" id="1c652" class="rm-shortcode" data-rm-shortcode-id="48097d5e9638b775b46ca579b7cd160d" data-rm-shortcode-name="rebelmouse-image" data-width="1440" data-height="960" />
The problematic Western diet
Credit: Vasiliy/Adobe Stock<p><span style="background-color: initial;"><a href="https://www.endocrineweb.com/conditions/type-1-diabetes/what-insulin" target="_blank">Insulin</a></span> is a hormone produced in the pancreas that regulates the level of glucose—a sugar found in many carbohydrates—by controlling its absorption into liver, fat, and skeletal muscle cells. If there's too much glucose in the blood, insulin stores away the extra sugar in the liver for later use when your blood sugar is low, or if you need a jolt of energy.</p><p>With <a href="https://www.diabetes.org/diabetes/type-2" target="_blank">type 2 diabetes</a>, the body no longer responds sufficiently to insulin. As a result, in an attempt to compensate and keep blood sugar at acceptable levels, the body increases its production of insulin, and this, over time, wears out the pancreas' ability to produce the hormone. At that point, the person requires injections of supplemental insulin to maintain blood sugar levels.</p><p>The most significant risk factor for developing type 2 diabetes is being overweight, which is typically a product of insufficient exercise and diet. "Type 2 diabetes is in fact a global pandemic and the number of diagnoses is expected to keep rising over the next decade," study co-leader Andrey Morgun of OSU tells the university's <a href="https://today.oregonstate.edu/news/research-shows-few-beneficial-organisms-could-play-key-role-treating-type-2-diabetes" target="_blank" rel="noopener noreferrer">Newsroom</a>. Driving this is the rising percentage of people who are <a href="https://www.who.int/news-room/fact-sheets/detail/obesity-and-overweight" target="_blank">overweight</a>. "The so-called 'western diet' — high in saturated fats and refined sugars," says Morgun, "is one of the primary factors. But gut bacteria have an important role to play in modulating the effects of diet."</p>
Tracing dysbiosis<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yNTI2MTUxNy9vcmlnaW4ucG5nIiwiZXhwaXJlc19hdCI6MTY2MDEzOTY2OX0.eXAjxosnEPKz0GKys-LJPS7exEl7Bj52bgafUHAC9SI/img.png?width=980" id="7e7cf" class="rm-shortcode" data-rm-shortcode-id="8ccfc6c33b2cf5285b3601915601cc56" data-rm-shortcode-name="rebelmouse-image" data-width="1440" data-height="810" />
Credit: Kathryn Cross/Ohio State University<p>The OSU study explores the microbial mechanism behind "dysbiosis," or microbiome imbalance, and its role in type 2 diabetes.</p><p>Co-author OSU's Natalia Shulzhenko says, "Some studies suggest dysbiosis is caused by complex changes resulting from interactions of hundreds of different microbes. However, our study and other studies suggest that individual members of the microbial community, altered by diet, might have a significant impact on the host."</p><p>The researchers used <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6557635/" target="_blank" rel="noopener noreferrer">transkingdom network analysis</a>, a recently developed data-driven, systems-biology methodology, to examine host-microbe interactions, looking for specific microbe species that might be involved in dysbiosis.</p><p>In fact, they found some. "The analysis pointed to specific microbes that potentially would affect the way a person metabolizes glucose and lipids," explains Morgun. "Even more importantly, it allowed us to make inferences about whether those effects are harmful or beneficial to the host. And we found links between those microbes and obesity." The first step was identifying four groups of closely related species, or operational taxonomical units (OTUs), that appeared to be associated with glucose management, and that may play a role in obesity as a precursor of type 2 diabetes.</p><p>The OTUs pointed to four microbial species in particular: <em>Lactobacillus johnsonii</em>, <em>Lactobacillus gasseri</em>, <em>Romboutsia ilealis</em>, and <em>Ruminococcus gnavus</em>. As Shulzhenko explains, "The first two microbes are considered potential 'improvers' to glucose metabolism, the other two potential 'worseners.' The overall indication is that individual types of microbes and/or their interactions, and not community-level dysbiosis, are key players in type 2 diabetes." (Previous research has also associated <em>Romboutsia ilealis</em>, or "<em>R. ilealis</em>", with obesity.)</p><p>That <em>Lactobacillus</em> is an improver is encouraging, as it's a species often found in existing probiotic supplements, yogurts, fermented foods, and some dairy products. Shulzhenko says that in "looking at all of the metabolites, we found a few that explain a big part of probiotic effects caused by Lactobacilli treatments."</p>
Of mice and men. And women.<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yNTI2MTU3My9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTY1MjUzODQ0Nn0.ng4zjkYhIX8qdERs5pBRnB-6A3omKxFR9026dT19-Sw/img.jpg?width=980" id="21fd2" class="rm-shortcode" data-rm-shortcode-id="3e9717ab4bd27bc26626b966d12d0ca2" data-rm-shortcode-name="rebelmouse-image" data-width="1440" data-height="792" />
Credit: Christoph Burgstedt/Adobe Stock<p>To confirm their suspicions, the researchers performed an experiment with mice, putting them on the mouse equivalent of the Western diet, and then feeding them improver and worsener microbe species for eight weeks.</p><p>Mice that were fed the two<em> Lactobacilli</em> improvers proved healthier in two ways. Their liver health—specifically, the efficiency with which they metabolized lipids and glucose—was improved, and they wound up with a lower <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7140880/" target="_blank">fat mass index</a> rating.</p><p>Comparing the results of their mice experiment with data from previous research on humans, the pattern held. The presence of more improver microbes was correlated with a lower BMI, and a stronger presence of worsens was associated with a higher <a href="https://www.cdc.gov/healthyweight/assessing/bmi/index.html" target="_blank">BMI</a>. Says Shulzhenko, "We found <em>R. ilealis</em> to be present in more than 80% of obese patients, suggesting the microbe could be a prevalent <a href="https://en.wiktionary.org/wiki/pathobiont" target="_blank" rel="noopener noreferrer">pathobiont</a> in overweight people."</p><p>The researchers hope that their findings can help lead to new prevention and treatment approaches for type 2 diabetes. Summarizes Morgun:</p><p style="margin-left: 20px;">"Our study reveals potential probiotic strains for treatment of type 2 diabetes and obesity as well as insights into the mechanisms of their action. That means an opportunity to develop targeted therapies rather than attempting to restore 'healthy' microbiota in general."</p>
The search for alien life is far too human-centric. Our flawed understanding of what life really is may be holding us back from important discoveries about the universe and ourselves.
- What, should it exist, is the universal law that connects all living things? To even dream of answering that question, and to one day find alien life elsewhere in the cosmos, humans must first reconcile the fact that our definition of life is inadequate.
- For astrobiologist Sara Walker, understanding the universe, its origin, and our place in it starts with a deep investigation into the chemistry of life. She argues that it is time to change our chemical perspective—detecting oxygen in an exoplanet's atmosphere is no longer sufficient enough evidence to suggest the presence of living organisms.
- "Because we don't know what life is, we don't know where to look for it," Walker says, adding that an unclear or too narrow focus could result in missed discoveries. Gaining new insights into what life on Earth is could shift our quest to find alien life in the universe.
Another amazing tardigrade survival skill is discovered.
- Apparently, some water bears can even beat extreme UV light.
- It may be an adaptation to the summer heat in India.
- Special under-skin pigments neutralize harmful rays.
Stressor testing<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yNDU1MzIzMS9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTYyMjc2MDc4Mn0.5R6DAfzsq29zvETCEH1sR9rprcnJv_L0KyUW2qedslE/img.jpg?width=980" id="c6b71" class="rm-shortcode" data-rm-shortcode-id="e7afe644fc94631ed9ea6837ed3920d3" data-rm-shortcode-name="rebelmouse-image" alt="water bear illustration" data-width="1440" data-height="810" />
3D illustration of a tardigrade
Credit: Dotted Yeti/Shutterstock<p>It seems at times like scientists enjoy playing the "let's see if <em>this</em> kills them" game with tardigrades, a game that humans usually lose. After searching the campus of the Indian Institute of Science, researchers gathered some water bears and brought them back to the lab to see what they could handle.</p><p>The scientists found that after they exposed <a href="http://cshprotocols.cshlp.org/content/2018/11/pdb.emo102301.full" target="_blank"><em>Hypsibius exemplaris</em></a> tardigrades to very high doses — 1 kilojoule (kJ) per square meter — of UV light for about 15 minutes, they would in fact die over the next 24 hours. However, when they aimed the same blasts at the reddish-brown tardigrades…nothing. The humans even quadrupled the UV intensity and, nope, they tracked the water bears for 30 days, and a majority of them, 60 percent, were still fine.</p><p>As is often the case with tardigrades, the question is how?</p>
Turning deadly light blue<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yNDU1MzIwMy9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTY3NDQyNzE2N30.nRWdnD8dEW1SDtC58xIUH-DeBgpNoL8QxEGFbZwU3N8/img.jpg?width=980" id="f0dfa" class="rm-shortcode" data-rm-shortcode-id="7aa8735a958123bcfb269920eb4d2aed" data-rm-shortcode-name="rebelmouse-image" data-width="3510" data-height="1039" />
Tardigrade's normal appearance (left), and under inverted fluorescence (right)
Credit: Suma et al., Biology Letters (2020)<p>When the researchers examined the tardigrades under an inverted fluorescence microscope they found that when they were exposed to UV light, they became blue. The researchers' hypothesis is that these tardigrades carry fluorescent pigments beneath their skin that they deploy as necessary to transform UV light into simple benign, blue light. It may be that this ability has emerged as an evolutionary response to southern tropical India's often-extreme heat. The study says that typical summer-day UV levels in this region are about 4kJ per square meter.</p><p>Of the 40 percent of the reddish-brown tardigrades that had died before 30 days — mostly after about 20 days — the scientists concluded they had less pigment with which to neutralize UV light.</p><p>When the scientists extracted the pigment from the UV champions and coated some <em>Hypsibius exemplaris</em> tardigrades with the stuff, their resistance to UV exposure was also enhanced, boosting their survival rate to almost twice that of their uncoated brethren.</p><p>Autofluorescence has been found in other animals — parrots, scorpions, chameleons, and frogs, among others — so it's not completely unheard of. In parrots, for example, autofluorescence is hypothesized to be involved in tweaking coloration during mating rituals. Still, surprise, tardigrades seem to be putting it to unusual use by employing it for UV protection. </p>
The microbes that eventually produced the planet's oxygen had to breathe something, after all.
- We owe the Earth's oxygen to ancient microbes that photosynthesized and released it into the world's oceans.
- A long-standing question has been: Before oxygen, what did they breathe?
- The discovery of microbes living in a hostile early-Earth-like environment may provide the answer.
Unassuming but remarkable microbial mats<p> Photosynthesis chiefly requires sunlight, water, and CO<sup>2</sup>. The CO<sup>2</sup> gets broken down into carbon and oxygen — the plant uses some of this oxygen and releases the rest. Without oxygen molecules, though, how did this work? </p><p> There are known microbial mats today that live in oxygen-free environments, but they're not thought to be sufficiently like their ancestors to explain ancient photosynthesis in an oxygen-free environment. </p><p> There have been a few oxygen stand-ins proposed. Photosynthesis can work with iron molecules, but fossil-record evidence doesn't support that idea. Hydrogen and sulphur have also been proposed, though evidence for them is also lacking. </p><p> The spotlight began to shift to arsenic in the first decade of the millennium when arsenic-breathing microbial mats were discovered in two hypersaline California lakes, <a href="https://science.sciencemag.org/content/308/5726/1305.abstract" target="_blank">Searles Lake</a> and <a href="https://www.discovermagazine.com/planet-earth/mono-lake-bacteria-build-their-dna-using-arsenic-and-no-this-isnt-about-aliens" target="_blank" rel="noopener noreferrer">Mono Lake</a>. In 2014, Visscher and colleagues <a href="https://www.nature.com/articles/ngeo2276" target="_blank">unearthed indications</a> of arsenic-based photosynthesis, or "arsenotrophic," microbial mats deep in the fossil record of the Tumbiana Formation of Western Australia. </p><p> Still, given the ever-shifting geology of the planets, the fractured ancient fossil record makes definitive study of ancient arsenotrophic photosynthesis difficult. The fossil record can't identify the role of the arsenic it reveals: was it involved in photosynthesis or just a toxic chemical that happened to be there? </p><p>Then, last year, arsenic-breathing microorganisms <a href="https://www.washington.edu/news/2019/05/01/arsenic-breathing-life-discovered-in-the-tropical-pacific-ocean/" target="_blank" rel="noopener noreferrer">were discovered</a> in the Pacific Ocean. A sulphur bacterium, <em>Ectothiorhodospira sp.</em> was also recently found to be metabolizing arsenic into <a href="https://en.wikipedia.org/wiki/Arsenite" target="_blank">arsenite</a> in <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5064118/" target="_blank" rel="noopener noreferrer">Big Soda Lake</a> in Nevada. </p>
An ancient Earth environment, today<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yNDQ0NzIxMC9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTY1OTQwOTYyN30.v96ZRXpIAf4yzDwcvXzVV3Fa4qULtUMxanXguPHD2wI/img.jpg?width=980" id="9eec4" class="rm-shortcode" data-rm-shortcode-id="a23585c057ee50ed500b96125e4a6b05" data-rm-shortcode-name="rebelmouse-image" data-width="2873" data-height="1640" />
a Map of Northern Chile; b Detail of frame showing Laguna La Brava in the southern Atacama; c The channel showing the mats in purple; d Hand sample, cross-section; e Microscopic image of bacteria.
Credit: Visscher, et al./Communications Earth & Environment<p>The study reports on Visscher's discovery of a living microbial mat thriving in an arsenic environment in Laguna La Brava in the Atacama Desert in Chile. "We started working in Chile," Visscher tells <a href="https://today.uconn.edu/2020/09/without-oxygen-earths-early-microbes-relied-arsenic-sustain-life/" target="_blank"><em>UConn Today</em></a>, "where I found a blood-red river. The red sediments are made up by <a href="https://en.wikipedia.org/wiki/Anoxygenic_photosynthesis" target="_blank">anoxogenic</a> photosynthetic bacteria. The water is very high in arsenic as well. The water that flows over the mats contains hydrogen sulfide that is volcanic in origin and it flows very rapidly over these mats. There is absolutely no oxygen."</p><p>The mats had not previously been studied, and the conditions in which they live are tantalizingly similar to those of early Earth. It's a high-altitude, permanently oxygen-free state with extreme temperature swings and lots of UV exposure. </p><p>The mats that somewhat resemble Nevada's purple <em>Ectothiorhodospira sp.</em> are going about their business of making carbonate deposits, forming new stromatolites. Most excitingly, those deposits contain evidence that the mats are metabolizing arsenic. The rushing waters surrounding the mats are also rich in hydrogen sulphide and arsenic.</p><p>Says Visscher, "I have been working with microbial mats for about 35 years or so. This is the only system on Earth where I could find a microbial mat that worked absolutely in the absence of oxygen."</p><p>Not that Earth is the only place where this could happen. Visscher notes that the equipment they used for studying the Laguna La Brava mats is not unlike the system aboard the Mars Perseverance Rover. "In looking for evidence of life on Mars, they will be looking at iron, and probably they should be looking at arsenic also."</p>