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Earth’s first lifeforms breathed arsenic, not oxygen
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.
One of the most interesting natural organizations studied by scientists are microbial mats, communities of cyanobacteria (AKA, "blue-green algae"). These fascinating self-contained ecosystems are visible to the naked eye and can be found all over the place: in lakes and streams, in soil, and even in man-made environs such as gutters and drinking fountains. Given enough time — say two to three thousand years — microbial mats fossilize layer-by-layer into carbonized stromatolites, our oldest fossils. They've been doing this for about 3.7 billion years.
Scientists believe these ancient microbial photosynthesizers are responsible for the oxygen we breathe. Prior to their arrival, the planet's atmosphere was only about 1 percent oxygen. What could they have been breathing for the first 1.5 billion years, and how did they execute photosynthesis without oxygen?
In a new study published in Communications Earth & Environment, researchers led by Pieter T. Visscher from the University of Connecticut present a convincing answer to the puzzle: The Earth's early oxygen-producing microbes were breathers and photosynthesizers of arsenic, however poisonous to us that may be now.
Unassuming but remarkable microbial mats
Photosynthesis chiefly requires sunlight, water, and CO2. The CO2 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?
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.
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.
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, Searles Lake and Mono Lake. In 2014, Visscher and colleagues unearthed indications of arsenic-based photosynthesis, or "arsenotrophic," microbial mats deep in the fossil record of the Tumbiana Formation of Western Australia.
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?
Then, last year, arsenic-breathing microorganisms were discovered in the Pacific Ocean. A sulphur bacterium, Ectothiorhodospira sp. was also recently found to be metabolizing arsenic into arsenite in Big Soda Lake in Nevada.
An ancient Earth environment, today
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
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 UConn Today, "where I found a blood-red river. The red sediments are made up by anoxogenic 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."
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.
The mats that somewhat resemble Nevada's purple Ectothiorhodospira sp. 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.
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."
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."
The team caught a glimpse of a process that takes 18,000,000,000,000,000,000,000 years.
- In Italy, a team of scientists is using a highly sophisticated detector to hunt for dark matter.
- The team observed an ultra-rare particle interaction that reveals the half-life of a xenon-124 atom to be 18 sextillion years.
- The half-life of a process is how long it takes for half of the radioactive nuclei present in a sample to decay.
Humans are particularly prone to shiver when a group does or thinks the same thing at the same time.
A few years ago, I proposed that the feeling of cold in one's spine, while for example watching a film or listening to music, corresponds to an event when our vital need for cognition is satisfied.
Certain colors are globally linked to certain feelings, the study reveals.
- Color psychology is often used in marketing to alter your perception of products and services.
- Various studies and experiments across multiple years have given us more insight into the link between personality and color.
- The results of a new study spanning 6 continents (30 nations) shows universal correlations between colors and emotions around the globe.
The root of color psychology<span style="display:block;position:relative;padding-top:56.25%;" class="rm-shortcode" data-rm-shortcode-id="9e40cf62fa8922fcca6c57e2fcb215b6"><iframe type="lazy-iframe" data-runner-src="https://www.youtube.com/embed/OM4fXB23pCQ?rel=0" width="100%" height="auto" frameborder="0" scrolling="no" style="position:absolute;top:0;left:0;width:100%;height:100%;"></iframe></span><p>There is a very likely chance you've even been "fooled" by color marketing in the past, or you've chosen one product over another subconsciously due to colors that were designed to influence your emotions.<br></p><p>Companies that want to be known for being dependable often use blue in their logos, for example (Dell, HP, IBM). Companies that want to be perceived as fun and exciting go for a splash of orange (Fanta, Nickelodeon, even Amazon). Green is associated with natural, peaceful emotions and is often used by companies like Whole Foods and Tropicana. </p><p><strong>Your favorite color says a lot about your personality. </strong></p><p>Various studies and experiments across multiple years (<a href="https://www.researchgate.net/publication/49595886_Personality_Traits_and_Colour_Preferences" target="_blank">2010</a>, <a href="https://onlinelibrary.wiley.com/doi/abs/10.1111/jopy.12087" target="_blank" rel="noopener noreferrer">2014</a>, <a href="http://oaji.net/articles/2015/1170-1448038739.pdf" target="_blank" rel="noopener noreferrer">2015</a>, and more recently in <a href="https://www.verywellmind.com/color-psychology-2795824#modern-research-on-color-psychology" target="_blank" rel="noopener noreferrer">2019</a>) have given us more insight into the link between your personality and your favorite color.</p><p>Red, for example, is considered a bold color and is associated with feelings such as excitement, passion, anger, danger, energy, and love. The personality traits of this color might be someone who is bold, a little impulsive, and who loves adventure. </p><p>Orange, on the other hand, is considered representative of creativity, happiness, and freedom. The personality traits of this color can be fun, playful, cheerful, nurturing, and productive. Read more about color psychology and personalities <a href="https://bigthink.com/mind-brain/color-personality-psychology?rebelltitem=2#rebelltitem2" target="_self">here</a>.</p>
Study reveals which colors best suit which emotions around the globe<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yNDYzMTk5OS9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTYyODc4OTg5OH0.bY-pu-MFNivdJLDJuBp9TBKrhwuy7hngUa1aIWxQMVw/img.jpg?width=1245&coordinates=0%2C93%2C0%2C94&height=700" id="33fff" class="rm-shortcode" data-rm-shortcode-id="1a5d7bb00dac94bd6201616789fb4882" data-rm-shortcode-name="rebelmouse-image" alt="concept of color psychology how colors make us feel color emotions" />
Certain colors are globally ties to certain emotions, the study reveals.
Image by agsandrew on Shutterstock<p>In this particular survey, participants were asked to fill out an online questionnaire which involved assigning 20 emotions to 12 different color terms. They were also asked to specify the intensity with which they associated the color term with the emotion.</p><p><strong>Certain colors are globally linked to certain emotions, the study reveals.</strong></p><p>The results of this study showed a few definite correlations between colors and emotions throughout the globe. Red, for example, is the only color that is strongly associated with both negative (anger) and positive (love) feelings. Brown, on the other end of the spectrum, is the color that triggers the fewest emotions globally.<br></p><p>The color white is closely associated with sadness in China, while purple is what is closely associated with sadness in Greece. This can be traced back to the roots of each culture, with white being worn at funerals in China and dark purple being the Greek Orthodox Church's color of mourning. </p><p>Yellow is more associated with joy, specifically in countries that see less sunshine. Meanwhile, its association with joy is weaker in areas that have greater exposure to sunshine. </p><p><a href="https://www.sciencedaily.com/releases/2020/09/200910150247.htm" target="_blank">According to Dr. Oberfeld-Twistel</a>, it is difficult to say exactly what the causes for global similarities and differences are. "There is a range of possible influencing factors: language, culture, religion, climate, the history of human development, the human perceptual system."</p>