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Learning Outcomes

  • Discuss the distinguishing features of extremophiles

Some organisms have developed strategies that allow them to survive harsh conditions. These adaptations, along with others, allow bacteria to be the most abundant life form in all terrestrial and aquatic ecosystems.

Other bacteria and archaea are adapted to grow under extreme conditions and are called extremophiles, meaning “lovers of extremes.” Extremophiles have been found in all kinds of environments: the depth of the oceans, hot springs, the Arctic and the Antarctic, in very dry places, deep inside Earth, in harsh chemical environments, and in high radiation environments, just to mention a few.

Other extremophiles, like radioresistant organisms, do not prefer an extreme environment (in this case, one with high levels of radiation), but have adapted to survive in it. For example, Deinococcus radiodurans, shown in Figure 1, is a prokaryote that can tolerate very high doses of ionizing radiation. It has developed DNA repair mechanisms that allow it to reconstruct its chromosome even if it has been broken into hundreds of pieces by radiation or heat.

These organisms give us a better understanding of prokaryotic diversity and open up the possibility of finding new prokaryotic species that may lead to the discovery of new therapeutic drugs or have industrial applications. Because they have specialized adaptations that allow them to live in extreme conditions, many extremophiles cannot survive in moderate environments.

There are many different groups of extremophiles: they are identified based on the conditions in which they grow best, and several habitats are extreme in multiple ways. For example, a soda lake is both salty and alkaline, so organisms that live in a soda lake must be both alkaliphiles and halophiles (Table 1).

Table 1. Extremophiles and Their Preferred Conditions
Extremophile TypeConditions for Optimal Growth
AcidophilespH 3 or below
AlkaliphilespH 9 or above
ThermophilesTemperature 60–80 °C (140–176 °F)
HyperthermophilesTemperature 80–122 °C (176–250 °F)
PsychrophilesTemperature of −15–10 °C (5–50 °F) or lower
HalophilesSalt concentration of at least 0.2 M
OsmophilesHigh sugar concentration

Prokaryotes in the Dead Sea

One example of a very harsh environment is the Dead Sea, a hypersaline basin that is located between Jordan and Israel. Hypersaline environments are essentially concentrated seawater. In the Dead Sea, the sodium concentration is 10 times higher than that of seawater, and the water contains high levels of magnesium (about 40 times higher than in seawater) that would be toxic to most living things. Iron, calcium, and magnesium, elements that form divalent ions (Fe2+, Ca2+, and Mg2+), produce what is commonly referred to as “hard” water.

Taken together, the high concentration of divalent cations, the acidic pH (6.0), and the intense solar radiation flux make the Dead Sea a unique, and uniquely hostile, ecosystem[1] (Figure 2).

What sort of prokaryotes do we find in the Dead Sea? The extremely salt-tolerant bacterial mats include Halobacterium, Haloferax volcanii (which is found in other locations, not only the Dead Sea), Halorubrum sodomense, and Halobaculum gomorrense, and the archaea Haloarcula marismortui, among others.

The Physiology of Paragliding Flight at Moderate and Extreme Altitudes

Wilkes, Matt, Martin J. MacInnis, Lucy A. Hawkes, Heather Massey, Clare Eglin, and Michael J. Tipton. The physiology of paragliding flight at moderate and extreme altitudes. High Alt Med Biol 19:42-51, 2018.-Paragliding is a form of free flight, with extreme-altitude paragliding being an emerging discipline. We aimed to describe the physiological demands and the impact of environmental stressors of paragliding at moderate and extreme altitudes. We recorded oxygen consumption (VO2), heart rate (HR), respiratory frequency (fR), tidal volume (VT), oxygen saturation, accelerometry (G), and altitude in 9.3 hours of flight at moderate altitudes (to 3073 m, n = 4), 19.3 hours at extreme altitude (to 7458 m, n = 2), and during high-G maneuvers (n = 2). We also analyzed HR data from an additional 17 pilots (138 hours) using the Flymaster Live database to corroborate our findings. All pilots were male. Overall energy expenditure at moderate altitude was low [1.7 (0.6) metabolic equivalents], but physiological parameters were notably higher during takeoff (p < 0.05). Pilots transiently reached ∼7 G during maneuvers. Mean HR at extreme altitude [112 (14) bpm] was elevated compared to moderate altitude [98 (15) bpm, p = 0.048]. Differences in pilots' VT and fR at moderate and extreme altitudes were not statistically significant (p = 0.96 and p = 0.058, respectively). Thus, we conclude that physical exertion in paragliding is low, suggesting that any subjective fatigue felt by pilots is likely to be cognitive or environmental. Future research should focus on reducing mental workload, enhancing cognitive function, and improving environmental protection.

Keywords: altitude extreme sports flight paragliding physiology. Life in Moderate and Extreme Environments - Biology

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Extremophiles: Hot Environments


Although thermophiles are limited to bacteria and archaea, they are found in a wide range of environments, including coal refuse, hot-water tanks, and compost piles. This article will focus only on thermophiles from geothermal environments and are divided into the following groups. Photosynthetic bacteria generally grow up to 70–75 °C and include many cyanobacteria as well as green- and purple-sulfur bacteria such as Chloroflexus and Chromatium. Spore-forming thermophiles include Bacillus, Clostridium, and Moorella species. Several thermophilic Actinomycetes have been described as well as thermophilic sulfur-oxidizers (e.g., Thiobacillus), sulfate reducers (e.g., Desulfovibrio), and Gram-negative aerobes (e.g., Thermus). Among archaea, thermophiles are often also acidophiles. Sulfolobus, Acidianus, and Metallosphaera are found in acidic terrestrial hot springs and have pH optima around pH 2. Aciduliprofundum boonei is a marine thermoacidophile recently found in deep-sea hydrothermal vents that grows optimally at pH 4.5, which highlights the potential importance of acidophily in marine environments as well. Methanogens are found in the thermophilic temperature range as well as the hyperthermophilic range.

The Mitochondria-Targeted Plastoquinone-Derivative SkQ1 Promotes Health and Increases Drosophila melanogaster Longevity in Various Environments

Mitochondria play an important role in aging. Strongly reduced function of the mitochondria shortens life span, whereas moderate reduction prolongs life span, with reactive oxygen species production being the major factor contributing to life span changes. Previously, picomolar concentrations of the mitochondria-targeted antioxidant SkQ1 were shown to increase the life span of Drosophila by approximately 10%. In this article, we demonstrate that SkQ1 elevates locomotion, which is often considered a marker of health and age. We also show that mating frequency and fecundity may be slightly increased in SkQ1-treated flies. These results indicate that SkQ1 not only prolongs life span but also improves health and vigor. An important property of any potential therapeutic is the stability of its effects in an uncontrolled and changing environment as well as on individuals with various genetic constitutions. In this article, we present data on SkQ1 effects on Drosophila longevity in extreme environments (low temperatures and starvation) and on individuals with severe genetic alterations in the mitochondrial systems responsible for production and detoxification of reactive oxygen species. We hypothesize that in vivo SkQ1 is capable of alleviating the probable negative effects of increased mitochondrial reactive oxygen species production on longevity but is not effective when reactive oxygen species production is already reduced by other means.

Keywords: Antioxidant Drosophila Life span Locomotion Reproduction.

Moderation Is the Key to Life

By Carlin Flora published July 4, 2017 - last reviewed on October 15, 2019

When a kid is tearing through a big bag of candy or enjoying a raucous game of indoor soccer near the étagére, the adult in the room will inevitably say, "This isn't going to end well." What an irritating comment to the child by her own logic she is having a good time and there is no way this marvelous activity could take a turn for the worse! Right before her stomach starts to ache, or grandma's favorite snow globe crashes to the floor, the child can be said to have reached the peak of her experience. A researcher studying this phenomenon would graph it as an inverted "U": The effects of a specific experience are more and more positive until maximum arousal occurs and the effects suddenly become more and more negative.

If you're bored with your job and feeling dull and sluggish, motivation is hard to muster. At the other extreme, if you're overwhelmed by tasks or suffering an emotional crisis, your brain is flooded with stress hormones. Your ability to plan and learn is impaired, and over time your immune and nervous systems are compromised. But when you're actively engaged in a project—a little nervous, a little excited—you've reached a happy medium. Optimal levels of adrenaline and cortisol boost your concentration and performance these hormones protect your body, in direct opposition to an excess of those substances hurting it. When you're optimally aroused, you're in flow, you're on top of the upside-down "U," and everything is juuust right.

In what's called "the Goldilocks effect," infants naturally tune in to experiences that are neither too simple nor too complex. Marketers know the golden mean as well: When presented with a product that is offered at low, medium, and high price points, the shopper typically chooses the middle option.

And yet, our culture valorizes extremes. "You can never be too rich or too thin" is a persistent message. People are no longer capable of watching just one favorite TV show they binge on whole seasons at a time, forgoing sleep and other basic needs. If you're a real-estate junkie, you can gawk at garish celebrity compounds with 21 bathrooms or 100-square-foot "micro houses." Many have no problem downing a Hardee's Monster Thickburger (1,300 calories) or a Sonic Peanut Butter and Cookie Dough Dream Master Blast (1,870 calories). An opposing camp includes those who recoil in horror at a teaspoon of added sugar or a gram of gluten. Anything that happens to anyone is "Super Awesome!" Or, "The. Worst. Thing. Ever."

"We have a 'more is better' algorithm built in," says Glenn Geher, a psychologist at SUNY New Paltz. "We evolved to like fatty food, but too much isn't good. Many substances or stimuli are beneficial in certain amounts, but then reach a tipping point after which they become harmful. We don't naturally moderate ourselves, because in ancestral conditions we didn't have to."

Many hover around the light-to-none end of the exercise spectrum, which is not surprising considering that early humans didn't have to gather the will to work out for an hour. "A more adaptive tendency for them was to move as little as possible to conserve energy," Geher says. "And that was fine, because with a nomadic lifestyle they were already getting way more exercise than the typical modern-day American."

Further, a short-term focus primes us to eschew moderation, claims Art Markman, a professor of psychology at the University of Texas, Austin. We all discount long-term interests to some degree, and impulsive people have an even stronger tendency to do so. "Many activities that we overdo in the moment have a negative impact somewhere in the future," he says. "No particular cigarette is the one that kills a person it's the accumulation of toxins over time that creates the negative health consequences. The motivational system doesn't take that long-term consequence strongly into account. It just decides: 'This feels really good right now, so let's do it.'" Even behaviors that are good only sometimes or pleasurable in the short-term, such as checking email, can scale up to an obsessive habit. The mere prospect of positive stimulation abets extreme digital behavior.

We've evolved to see things in black and white, rather than shades of gray. If you have to make life-or-death decisions about others in a split second, blunt categories are useful even in low-stakes situations, putting people in buckets can be efficient. It's simpler to declare: My ex is a raging narcissist, rather than: Yes, my ex is quite high on the scale on some components of narcissism, but I also played a role in the dynamic that led him to leave. Nuanced assessments are mentally taxing, extreme labels are quick and easy to apply.

Balanced Behavior

The prevailing view of the positive psychology movement is that cultivating one's strengths and amping up positive feelings is always a worthy goal. But given that the inverted-U curve captures so much about human nature, Adam Grant, of the University of Pennsylvania, and Barry Schwartz, of Swarthmore College, were skeptical that that was invariably true. Indeed, in a 2011 literature review in Perspectives on Psychological Science, they found evidence supporting the notion that endlessly increasing "good" emotions and states is not always beneficial.

Take the concept of authenticity. Being a fake and a liar won't get you far, but people who claim to be "highly authentic" at work receive lower performance evaluations than others and are less likely to be promoted. Caring a lot about "doing you" prevents change and growth, and can lead to disclosing too much personal and sensitive information to others. Instead, Grant recommends striving to present a better version of yourself, rather than straining to make your inner self transparent.

It's an insight rooted in ancient wisdom: In Aristotle's enduring view, too little expression of certain traits, such as courage (cowardice), is undesirable while too much of the same trait constitutes a different character flaw (recklessness). Not pleasing others enough amounts to surliness, pleasing too much makes one obsequious—you have to be friendly, but not too friendly. The sweet spot in the middle is where you want to be.

Moderation is intrapersonally important, too. Sporting an always-sunny nature can hurt you. Extremely cheerful people earn lower salaries and even live shorter lives because they are often risk takers. Likewise, moderate levels of positive emotions fuel creativity, but high levels don't. An excess of self-esteem is associated with work, health, and relationship woes. Even generosity and empathy have negative side-effects when doled out in high doses. Too much generosity consumes so much of the giver's time and energy that it causes burnout empathic overarousal can cloud judgment, cause bleeding hearts to back off to manage their own distress, or lead to sacrificial behavior that ultimately hurts more than it helps.

In The Upside of Your Dark Side, psychologists Robert Biswas-Diener and Todd Kashdan argue that you'll have a more meaningful and engaging life if you tap into the full range of emotions, including those seen as socially undesirable, such as anger. In a study published in the Journal of Anxiety Disorders, for example, Kashdan found that highly socially anxious people have more anger, and also suppress their anger more, than others do.

The point, explains Kashdan, a professor of psychology at George Mason University, isn't that we should never suppress anger. In a strong pitch for moderation, he notes, "There is ample evidence that habitual, reflexive emotion suppression is detrimental. Yet, uninhibited, impulsive, and tactless emotion expression may be equally damaging."

When we push aside uncomfortable feelings (a pain-killer reflex that is well developed in our comfort-obsessed society), we deny ourselves the opportunity to learn from important indicators. Kashdan says the first step to moderating emotions is to analyze your own prejudices and figure out which emotional expressions are most effective in specific situations. "You have to recognize your own behavioral signatures. Which emotions are you allergic to? Remember that cultural and social contexts alter the benefits and costs of traits."

When you're angry, you don't have to lash out wherever you happen to be, Kashdan says. "But it's not about calming yourself, either. It's about being aware that your anger is a signal that someone or something is obstructing one of your goals. It could be a false signal, but if you think it's accurate, follow through and try to effectively remove the obstacle." Civil rights, for instance, aren't won without righteous indignation. "Anger is a tool that you want in your psychological Swiss army knife. If you don't understand and appreciate both the selfish and the altruistic motivations of others, you will not fare well," he adds. "Owning both sides allows you to flexibly deal with a variety of people and situations."

Attenuated Love

Love naturally takes extreme forms: Many neurochemical investigations have shown that during the early "infatuation" phase, your body pumps out high levels of norepinephrine, dopamine, and testosterone, leaving you euphoric and drawn to your new love as though he were a drug. It's a mechanism that evolved to make sure we bond and reproduce with others, a mission so important, it has no patience for half measures. Over the course of about two years, infatuation tends to give way to an "attachment" phase, characterized by an increase in vasopressin and oxytocin and by feelings of security and contentment rather than unbridled passion.

Yet some people, particularly those whose love is unrequited, remain in limerence—a hyped-up but more anxious and tortured state—for years, unable to break the spell. Albert Wakin of Sacred Heart University, an expert on limerence, thinks of it as a combination of obsessive-compulsive disorder and addiction (to another person). He reports that 5 percent of people who suffer limerence have trouble shaking it, to the point where they can't function well in their day-to-day life and spend up to 95 percent of their time thinking of their beloved. Social media fuels this form of romantic intensity as it provides constant updates about and photos of the person who is already looming too large in their mind.

In one study, researchers found that those who experience rejection while still in the infatuation phase can experience profound feelings of loss and depression (the heartache most of us are familiar with) and can even be moved to engage in the most extreme of all behaviors: suicide or homicide. The areas of the brain activated in the romantically forlorn are the same as those involved in cocaine addiction, which, study authors conclude, may help explain how otherwise stable people can get obsessive when spurned.

Though it's short of outright rejection, ambivalence is powerful fuel for what researchers call "the unrequited love narrative." In Unrequited: Women and Romantic Obsession, journalist Lisa Phillips wrote about her own gripping belief that her doomed love story would have a happy ending. She fell in love with an unavailable man who hemmed and hawed over whether he should leave his girlfriend for her. She focused on him obsessively and couldn't stop herself from calling, messaging, and following him. "I was responsible for my extreme behavior," Phillips says. "And I was responsible for the fact that this person was treating me poorly and I was tolerating it. I now know that extreme feeling for someone else has nothing to do with whether or not you can have a fulfilling relationship over the long term. It's important to pay attention to the 'why,' when you love someone asymmetrically."

At the other end of the love scale sit those who avoid it, despite needing it. The desire to belong and to be close to others is universal, but those with an "avoidant" (as opposed to a "secure" or "ambivalent") attachment style tend to push others away when they sense their independence is being threatened. Forged in childhood, attachment style is the way we tend to respond to the availability of partners or potential partners. Researchers estimate that about 20 percent of the population have an avoidant orientation. Psychiatrist Amir Levine and therapist Rachel S.F. Heller, the authors of Attached, recommend that avoiders pair up with people who have a secure attachment style, since an anxiously attached partner will continually annoy an avoidant. Conscious awareness of our own patterns can, over time, override or, at least, let us live happily with these ingrained modes of relating.

To counteract the unrealistic ideal of a committed relationship marked by constant desire and heroic sacrifices, Aaron Ben-Zeév, professor of philosophy at the University of Haifa, touts the notion of "mild love," characterized by calmness, caring, kindness, and loyalty. It's the steady diet of simple pleasures that is essential. Moderation is sometimes best achieved over the long term, when less passion may be offset by moments of intense passion (or at least rosy memories of an initial infatuation).

Moderate Appetites

A key to moderation is not becoming fixated on one part of life but, instead, taking a big-picture view so that assessing your overall balance of priorities is possible. A total preoccupation with food, for instance, is not only extreme but ineffective. "What you eat and drink is not everything when it comes to your health and longevity," says Susan McQuillan, a dietician and food writer. "Exercise is important, as are other lifestyle habits, stress levels, and family history. Some people put too much emphasis on food and think they're controlling everything with what they eat. We all know people who lived into their 90s and ate convenience foods every day."

"The classic rule for nutritionists is that there are no good foods, there are no bad foods, and you should eat everything in moderation," says McQuillan. "Some foods are not the best source of nutrients, but they still provide energy. When my daughter was young, we ate healthily most of the time, so I didn't have to worry about what she ate at a birthday party."

That sounds reasonable, but human hankerings go wild in an environment where engineered-to-binge snacks, such as Cheetos and Oreos, can be bought at every corner. Planning and cooking well-balanced meals is often a lot harder than turning to the extremes of a processed-food regimen or a restrictive "healthy" diet that limits the burden of choice. So-called "health foods" are often far from it: A fridge full of pressed juice in pretty bottles is appealing, yet all that "detoxifying" may actually flood your body with sugar.

It's true that a plan to eat in moderation might justify a varied diet that is actually worse than a less-varied diet focused on fruits, vegetables, and lean protein. A 2015 study out of the University of Texas Health Science Center at Houston found that diet diversity, or less similarity among the foods one eats, might be linked to lower diet quality and worse metabolic health. But if you know you are not going to fall into the "all healthy, all the time" category anyway, then aiming for diversity may at least keep junk-food cravings in check.

McQuillan's centrist strategy for living with a sweet tooth involves never buying cookies, though she does bake them from scratch. "Don't tell yourself you can't have sweets at all, because you're just going to rebel and overdo it," she says. One study of dieters confirms this advice: Those allowed a planned "cheat day" when they could indulge in treats were more motivated and able to follow through with their diet. They were also in a better mood throughout the process. Another study published in the Journal of Health Psychology in 2015 found that dieters consume more food after exercising than nondieters do, calorically canceling out their effort.

Moderation and mindfulness go hand in hand: A 2016 study led by Jennifer Daubenmier at the University of California, San Francisco, shows that bringing awareness to the present moment and savoring food leads people to make better choices and recognize when they are hungry, satisfied, or full.

Alcohol's inherent disinhibiting effect makes it a particularly hard substance to consume moderately. However, total abstinence is too draconian for some and can trigger failure—a little relapse can lead to a hard fall off the wagon. A comprehensive review in the journal Clinical Psychology of the "harm reduction" method, in which therapists work with alcoholics to limit the amount they drink, found that these interventions are effective for some people because their imbibing is viewed in more than black-and-white, all-or-nothing terms.

Middle-of-the-Road Work Habits

Adherents of the American Dream believe that working to the max is the secret to success. But Grant and Schwartz, in their analysis of the prevalence of inverted-U-shaped effects, found strong evidence that moderation also gets results on the job. For example, "learning orientation" is the extent to which bosses encourage proactive learning and competence development among their employees. One study that Grant and Schwartz reviewed had examined management teams in a Fortune 100 company and discovered that those with moderate (as opposed to high or low) learning orientations earned the most profits.

In an earlier study led by Ellen Langer, of Harvard, researchers asked people to translate sentences into a new made-up language. Subjects who practiced the language moderately beforehand made fewer errors than those who practiced extensively or not at all. High levels of knowledge can make people too attached to traditional ways of viewing problems across fields—the arts, sciences, and politics. High complexity in a job role exacerbates stress, burnout, and dissatisfaction. High conscientiousness is related to lower job performance, especially in simple jobs where it doesn't pay to be a perfectionist.

How long we stay on the clock and how we spend that time are under great scrutiny in many workplaces. The young banker who eats lunch at his desk is probably seen as a go-getter, while his rambunctious colleagues who laugh and gossip over a leisurely conference-room meal get dirty looks from the corner office. "People from cultures that value relationships more than ours does are appalled by the thought of eating alone in front of a computer," Markman says. Social interaction has been shown to boost mood and get people thinking in new directions and in ways that could enhance any postlunch effort.

Markman also promotes off-task time. "Part of being a good thinker is encountering things that are seemingly unrelated to what you are working on at the moment but give you insights into your work," he says. "Also, a work day that drags on too long crowds out other sources of life satisfaction, such as relationships. There is a lot of research showing that a positive mood leads to higher levels of productivity and creativity. So, when people do things to boost their life satisfaction, they also make themselves more effective at work."

Many prolific and prominent professionals build flexibility and leisure time into their schedules. Stephen King writes for a few hours in the morning, and then may or may not return to his desk in the afternoon. Even Charles Darwin reportedly dedicated just four hours per day to serious tasks. According to neuroscientist Josh Davis, the author of Two Awesome Hours, an even lighter schedule is sufficient, as long as conditions—such as not being tired or hungry—are right for peak productivity.

A creative person enraptured in a project, barely pausing for a drink of water, is a compelling image and might capture how some great works come about. But researchers make a distinction between "obsessive" and "harmonious" passions, with the latter coming out ahead. Scott Barry Kaufman, the scientific director of the Imagination Institute, based at the University of Pennsylvania, explains that people who are obsessively on-task are rigid and find it hard to disengage. Their habits put them at risk of burning out. Meanwhile, harmonious passion is correlated with the joyful state of being fully immersed in an activity.

Dare to Be Average

Setting up camp in the middle ground requires some thought and planning. Markman, the author of the book Smart Change, notes that you have to make certain things quite hard to do. "The motivational system is very good at clearing the decks for action. When you really want ice cream, you become more sensitive to information that relates to acquiring it. When I lost a lot of weight 15 years ago, I made the remarkable discovery that you can't eat ice cream that's not in your freezer."

Markman applies moderate thinking to many areas of life. He and his wife have a pact: They don't bring their phones into restaurants, so they won't be tempted to take a peek. And if his kids want to sit in the front passenger seat, they have to put their phones away so they can be engaging companions.

Replacing bad habits with good ones and establishing healthy systems for living moderately is easier when you have an underlying philosophical motivation to do so. If you value flexibility in setting goals and relating to loved ones, precision in thinking and speaking, and sympathy in judging other people, and you reject lazy, simplistic reasoning and mindless actions, then you're a true believer in the middle ground.

Moderation in All Things. Even Moderation

Every great rule has exceptions, and there's a time and place for extremism.

When the writer Samuel Johnson once walked into a party, someone said to him, "Will you take a little wine?" Johnson replied, "I can't take a little. Abstinence is as easy to me as temperance would be difficult." When Gretchen Rubin, the author of Better Than Before, read this anecdote, she immediately recognized herself (though her poison is sugar, not alcohol). It led to her concept of dividing people, for self-help purposes, into "abstainers" and "moderators."

"This distinction has to do with how people resist strong temptations, because everybody can be moderate about weak temptations," Rubin says. "I'm a hard-core sugar abstainer, but I can take or leave potato chips." People assume Rubin is an abstainer because she has a lot of willpower. "The fact is, I don't have enough willpower to have a little bit of sugar. It's easier to have none." Banning frees her from having to make constant internal negotiations about which and how many candies, brownies, and cookies she can have.

"It's not about what worked for some billionaire, it's about what works for you."

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A microbe's membrane helps it survive extreme environments

Credit: CC0 Public Domain

Within harsh environments like hot springs, volcanic craters and deep-sea hydrothermal vents – uninhabitable by most life forms – microscopic organisms are thriving. How? It's all in how they wrap themselves.

Stanford University researchers have identified a protein that helps these organisms form a protective, lipid-linked cellular membrane – a key to withstanding extremely highly acidic habitats.

Scientists had known that this group of microbes – called archaea – were surrounded by a membrane made of different chemical components than those of bacteria, plants or animals. They had long hypothesized that it could be what provides protection in extreme habitats. The team directly proved this idea by identifying the protein that creates the unusual membrane structure in the species Sulfolobus acidocaldarius.

The structures of some organisms' membranes are retained in the fossil record and can serve as molecular fossils or biomarkers, leaving hints of what lived in the environment long ago. Finding preserved membrane lipids, for example, could suggest when an organism evolved and how that may have been the circumstance of its environment. Being able to show how this protective membrane is created could help researchers understand other molecular fossils in the future, offering new evidence about the evolution of life on Earth. The results appeared the week of Dec. 3 in Proceedings of the National Academy of Sciences.

"Our model is that this organism evolved the ability to make these membranes because it lives in an environment where the acidity changes," said co-author Paula Welander, an assistant professor of Earth system science at Stanford's School of Earth, Energy & Environmental Sciences (Stanford Earth). "This is the first time we've actually linked some part of a lipid to an environmental condition in archaea."

The hot springs where S. acidocaldarius is found, such as those in Yellowstone National Park that are over 200 degrees Fahrenheit, can experience fluctuating acidity. This organism is also found in volcanic craters, deep-sea hydrothermal vents and other acidic environments with both moderate and cold temperatures.

Welander became interested in studying this microbe because of its rare chemistry, including its unusual lipid membranes. Unlike plants and fungi, archaeal organisms do not produce protective outer walls of cellulose and their membranes do not contain the same chemicals as bacteria. Scientists had explored how the species produced its unusual membrane for about 10 years before experimentation stopped in 2006, she said.

"I think we forget that some things just haven't been done yet – I've been finding that a lot ever since I stepped into the geobiology world," Welander said. "There are so many questions out there that we just need the basic knowledge of, such as, 'What is the protein that's doing this? Does this membrane structure really do what we're saying it does?'"

From previous research in archaea, Welander and her team knew that the organisms produce a membrane containing a ringed molecule called a calditol. The group thought this molecule might underlie the species' ability to withstand environments where other organisms perish.

To find out, they first went through the genome of S. acidocaldarius and identified three genes likely to be involved in making a calditol. They then mutated those genes one-by-one, eliminating any proteins the genes made. The experiments revealed one gene that, when mutated, produced S. acidocaldarius that lacked calditol in the membrane. That mutated organism was able to grow at high temperatures but withered in a highly acidic environment, suggesting that the protein is necessary to both make the unusual membrane and withstand acidity.

The work was particularly challenging because Welander's lab had to replicate those high temperature, acidic conditions in which the microbes thrive. Most of the incubators in her lab could only reach body temperature, so lead author Zhirui Zeng, a postdoctoral researcher in Welander's lab, figured out how to imitate the organism's home using a special small oven, she said.

"That was really cool," Welander said. "We did a lot of experimenting to try to figure out the chemistry."

This work is about more than just finding one protein, Welander said. Her research explores lipids found in present-day microbes with the goal of understanding Earth's history, including ancient climatic events, mass extinctions and evolutionary transitions. But before scientists can interpret evolutionary characteristics, they need to understand the basics, like how novel lipids are created.

Archaea are sometimes called the "third domain of life," with one domain being bacteria and the other being a group that includes plants and animals – collectively known as eukaryotes. Archaea includes some of the oldest, most abundant lifeforms on the planet, without which the ecosystem would collapse. Archaea are particularly anomalous microbes, confused with bacteria one day and likened to plants or animals the next because of their unique molecular structures.

The research is particularly interesting because the classification for archaea is still debated by taxonomists. They were only separated from the bacteria and eukaryote domains in the past two decades, following the development of genetic sequencing in the 1970s.

"There are certain things about archaea that are different, like the lipids," Welander said. "Archaea are a big area of research now because they are this different domain that we want to study, and understand – and they're really cool."


Wilkes, Matt, Martin J. MacInnis, Lucy A. Hawkes, Heather Massey, Clare Eglin, and Michael J. Tipton. The physiology of paragliding flight at moderate and extreme altitudes. High Alt Med Biol 19:42–51, 2018.—Paragliding is a form of free flight, with extreme-altitude paragliding being an emerging discipline. We aimed to describe the physiological demands and the impact of environmental stressors of paragliding at moderate and extreme altitudes. We recorded oxygen consumption (VO2), heart rate (HR), respiratory frequency (fR), tidal volume (VT), oxygen saturation, accelerometry (G), and altitude in 9.3 hours of flight at moderate altitudes (to 3073 m, n = 4), 19.3 hours at extreme altitude (to 7458 m, n = 2), and during high-G maneuvers (n = 2). We also analyzed HR data from an additional 17 pilots (138 hours) using the Flymaster Live database to corroborate our findings. All pilots were male. Overall energy expenditure at moderate altitude was low [1.7 (0.6) metabolic equivalents], but physiological parameters were notably higher during takeoff (p < 0.05). Pilots transiently reached ∼7 G during maneuvers. Mean HR at extreme altitude [112 (14) bpm] was elevated compared to moderate altitude [98 (15) bpm, p = 0.048]. Differences in pilots' VT and fR at moderate and extreme altitudes were not statistically significant (p = 0.96 and p = 0.058, respectively). Thus, we conclude that physical exertion in paragliding is low, suggesting that any subjective fatigue felt by pilots is likely to be cognitive or environmental. Future research should focus on reducing mental workload, enhancing cognitive function, and improving environmental protection.

Artemia salina (Sea Monkey)

De Agostini Picture Library / Getty Images

Artemia salina (sea monkey) is a brine shrimp that is capable of living in conditions with extremely high salt concentrations. These extremophiles make their homes in salt lakes, salt swamps, seas, and rocky coasts. They can survive in salt concentrations that are almost saturated. Their primary food source is green algae. Like all crustaceans, sea monkeys have an exoskeleton, antennae, compound eyes, segmented bodies, and gills. Their gills help them survive in salty environments by absorbing and excreting ions, as well as by producing a concentrated urine. Like water bears, sea monkeys reproduce sexually and asexually via parthenogenesis. Life in Moderate and Extreme Environments - Biology

Acidophiles are life-forms that grow preferentially in natural or man-made environments where the pH is well below seven. Together with other categories of extremophiles, they have greatly expanded our knowledge of the diversity of life, our understanding on how microorganisms can adapt to seemingly hostile situations, and provided scenarios for the possibility that life-forms may be found outside of our solar system.

Written by experts in their field, this important volume provides a comprehensive account of acidophilic microbiology from fundamental to applied aspects. The seventeen chapters are arranged in five sections, each dealing with a specific area. The first section looks at the challenges faced by life-forms that grow in extremely acidic environments and how they adapt to meet these challenges. The next section describes the physiological and phylogenetic diversities of acidophilic microorganisms including archaea, bacteria and eukaryotes. Section three covers acidophile community dynamics, quorum sensing and the formation of biofilms. The next section deals with the various omic technologies that are used to study acidophiles including genomic and metagenomic studies, proteomic-, mobilomic- and metabolomic-focused research. The final section considers the ways in which acidophiles are used in established and emerging biotechnologies and describes why these fascinating microorganisms are considered potential candidates for life on other solar bodies, such as Mars, and beyond.

This up-to-date and comprehensive book will be indispensable for environmental scientists and microbiologists and is a recommended acquisition for all microbiology libraries.

"Contributors from a wide range of biological and environmental sciences" from ProtoView

"an excellent book on acidophiles with contributions by a broad international group . The contributions are well organized . The content is data driven, well documented, well referenced, and easily read. The flow from section to section is excellent. This is a book that will be useful to general microbiologists as well as environmental microbiologists and environmental engineers." from SIMB News

This Chapter introduces the subject of acidophile microbiology, tracing its origins to the current status quo, and provides the reader of this textbook with general information which provides a backdrop to the more specific topics described in subsequent chapters.

Environmental signals and molecular mechanisms that underlay the biofilm life-style have been largely characterized for bacteria that colonize human cavities. In contrast, the genetic basis that enable environmental acidophiles to form and develop biofilms are far from comprehended. Nonetheless, the molecular mechanisms that govern the biofilm developmental processes in a few model acidophiles have begun to be elucidated. This chapter describes what is currently known on the cellular and molecular mechanisms that promote biofilm formation of bacteria and archaea inhabiting extremely acidic ecosystems.

(EAN: 9781910190333 9781910190340 Subjects: [microbiology] [bacteriology] [environmental microbiology] [extremophiles] )

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