Extreme Sport Champions: Humans or Microbes?
Extreme Sport Champions: Humans or Microbes?
By John Warhol
Each time I watch an extreme sport, whether it’s the Tour de France, an Ironman Triathlon, or the Cooper’s Hill Cheese Rolling Race in Gloucestershire, England, I’m truly impressed by the skill, stamina, and determination of the athletes! Dexterity and fine motor control are important elements in many of these sports (as is bravery), but plain old-fashioned toughness is essential. No doubt, a human needs a high degree of fortitude to handle the heat of a Marathon in the Sahara, the freezing cold of ice climbing, or the squeezing barometric pressure at great depths in freediving. Yet whenever I see one of these elite and somewhat crazy athletes, I find myself asking “Are they tougher than a microbe?”
Cold Temperature
Let’s start with cold sports like skiing, or any activity that has the word “ice” in it. Sure, humans participate with enthusiasm, but are they naked (like a microbe)? Usually not! People are on death’s door when their body temperature drops to around 20 to 28 °C (68 to 82 °F). Not so for microbes, who populate an entire class of extreme cold-loving (psychrophilic) organisms. My favorite (an unfair description, because they’re all my favorites) is the genus Modestobacter. The type species, Modestobacter multiseptatus was discovered on the Linnaeus Terrace of Antarctica (from the Asgard Range, if that isn’t the coolest thing, for all you Thor fans) where summer temperatures vary between -15 °C and 0 °C, winter temperatures can fall to -60 °C (-76 °F), and the wind can reach howling speeds of 200 miles per hour (320 km/h). In the lab, some strains grow at 0 °C, but they are so lethargic that a decent growth curve takes around 8 weeks to perform! Related Modestobacter species also like the cold; Modestobacter marinus likes low temperature and high pressure, having been discovered in 2 °C water, 3,000 meters undersea, where the pressure is reported to be (choose your favorite units) 300 atm or 4400 psi or 3000kPa or 633,600 pounds per square foot!
High Pressure
Pressure-loving microbes were no doubt the inspiration for the famous Rock n Roll hit Under Pressure, a Queen-David Bowie collaboration from 1981, still getting airplay today, which reached the Top Ten hit chart in more than 10 countries around the world. (Maybe not exactly the inspiration, but Sir Brian May, lead guitarist for the band, has a PhD in physics and most certainly knows that P 1 V 1 = P 2 V 2 .) Most of these organisms are found in sediments on the ocean floor at great depth, a zone that accounts for about 75% of the total ocean volume, so there are potentially uncountably high numbers of these baro- or piezophilic microbes. One of my favorite pressure-lovers is the genus Colwellia, named for the great microbiologist Rita Colwell. The first of these microbes, discovered in 1988, was Colwellia hadaliensis followed by another 20 other species over the next several decades. Colwellia organisms have been found at depths of 6,300 meters (20,000 feet or 3.9 miles!) where the pressure is 60 megapascals or 8,700 psi, which is roughly equivalent to the pressure exerted when a shotgun shell is ignited. Colwellia also tend to love water just above freezing temperature, having been isolated from both Arctic and Antarctic regions. In contrast to Colwellia and other microbes, a genuine human barophile, Herbert Nitsch, holds the title of “Deepest Man on Earth” for his free dive to 214 meters (702 feet), where the pressure is a “mere” 325 psi or 22 atm.
High Temperature
There’s more happening in the ocean depths than extreme cold and pressure; there’s also extreme heat and pressure, if you know where to look! Areas of the deep ocean are sites of intense volcanic activity where hydrothermal vents can spew out superheated water at 163 °C (325 °F) while the surrounding water is 4 °C. One of the organisms isolated from this briny hot tub is Idiomarina loihiensis, discovered near the submarine volcano Lō’ihi near Hawaii. Hydrothermal vents are home to great populations of chemoautotrophic microbes that happily form the basis of the submarine food chain by synthesizing nutrients in total darkness (unlike our terrestrial friends, plants, that need sunlight for photosynthesis). Hydrothermal vents are among the most interesting ecologic niches that you could imagine. For example, a “black smoker” hydrothermal chimney (at around 2500 meters deep) was covered with deep sea creatures known as Pompeii worms, a type of bristle worm. The worms’ backs were covered in colonies of the microbe Nautilia profundicola. But the worms weren’t content to just sit near the vent, they sit half-in half-out, so that one part of their body is in 80 °C (176 °F) water in the vent and the rest of its body in 22 °C (72 °F) water outside the vent. The worms secrete mucus that is believed to be nutrient source for the Nautilia, which may provide enzymes that enable the worms to be heat-resistant.
High temperatures are not just for marine organisms. Thermus aquaticus was discovered in a geyser in Yellowstone National Park, Wyoming, USA. The microbe is perfectly happy living in water at around 160 °F (71 °C) and can survive from temperatures from 120 to 180 °F (49 to 82 °C). Thermus is an amazing, hard-working organism, not a vain social media personality that got famous by saying “I’m hot!” Thermus aquaticus is the original source of high speed, high temperature DNA polymerase that makes it possible to perform automated PCR rapidly and reliably. Every Crime Scene Investigation drama that uses DNA evidence owes its success to Thermus.
But humans? The usual medical advice is that people limit their hot tub time to around 20 minutes at 104 °F (40 °C). If you’re not in a hot tub, a “wet bulb” temperature of 95 °F (35 °C) is not survivable for more than a few hours; a wet bulb thermometer considers both temperature and humidity. When our body temperature reaches 105 °F (40.5 °C), we’re in the danger zone for heat stroke.
Radiation and More!
There’s much more to competing with microbes than just temperature and pressure; there are wonderful events like radiation soaking, toxin eating, acid bathing, and G-force loading. Whereas standing in front of a microwave oven or a nuclear reactor might scare you, it wouldn’t phase Rubrobacter radiotolerans. Discovered in a hot spring in Japan in 1973, this organism can withstand 500,000,000 millirems of gamma radiation, which is about 500 times more than a mere human. Other species of this pink bacterium, like R. taiwanensis are similarly radiation resistant.
Toxin munching
Toxin consumption is always a wonderfully competitive sport; here in the USA each year on July 4 we have a hot dog eating contest in which the winner needs to eat more than 60 hot dogs in 10 minutes to be victorious. Admittedly, hot dogs aren’t really toxic, and ten minutes is very quick, even for a bacterium, but bacteria are much better than humans at digesting genuine toxins over long time periods. For example, members of the genus Arthrobacter, a soil microbe, can metabolize the carcinogenic compound hexavalent chromium. They can also degrade pesticides, including chlorophenols and organophosphates. Neptunomonas naphthovorans was discovered in a highly toxic Superfund site in Puget Sound, Washington where it was cheerfully growing amid creosote and coal tar contaminated soil and sediment. Creosote is a tarry preservative that gives old-fashioned fishing piers their characteristic scent. Most remarkably, it was noted to consume naphthalene, the white crystalline solid used in mothballs. I certainly could not eat naphthalene!
Acid, base, and salt bathing
But consuming toxins is nothing compared to taking a long bath in acids, bases, or high salt solutions. Our inner workings usually function at around pH 7.4; a pH below 6.9 or above 7.8 is often lethal, and the concentration of salt in our blood is around 0.9%. Many bacteria would scoff at such weakness. For example, the genus Amphibacillus has species that will grow at pH 10 and around 20% salt concentration (as do Marinobacter and Oceanobacillus species). At the other end of the scale, Thiobacillus species enjoy living in acid at pH 2, and Geobacillus species enjoy almost the full range of the scale, from pH 2 to pH 12. Salinibacter is literally at the top of the heap (of salt) when it comes to saline environments; the organisms cannot live below 15% salinity and prefer between 20% and 30% salt concentration.
Pulling g’s
“How many G’s can you take?” is a routine conversation topic for jet fighter pilots and astronauts. Most fighter pilots can manage 9G for a second or two, sustained 6G is pretty much fatal, and nobody could survive a crash of 18Gs. But what of the humble flea? When a flea jumps, it accelerates at 100 to 130Gs, this means that every organism within the flea’s microbiome is subject to the same acceleration. Recent studies have found species of Bartonella, Rickettsia, and Wolbachia in fleas, which makes them much more G-force tolerant than humans!
Longest Race
And let’s not forget the longest competition – longevity. Even though microbes can reproduce at outstanding velocity, with populations doubling every 20 to 30 minutes under the right conditions (clearly humans can’t win the reproduction competition either) they excel at not reproducing and just kicking back and going to sleep. Often for centuries. A wonderful example is from the genus Kurthia, which was isolated from a mammoth that died 40,000 years ago. But this pales in comparison to microbes that woke up in 2020 after a nap lasting 101 million years at the bottom of the Pacific Gyre. These long-lived slumbering organisms included members of Actinobacteria, Bacteroidetes, Firmicutes, Alphaproteobacteria, Betaproteobacteria, Gammaproteobacteria, and Deltaproteobacteria.
Fastest Race
It may look like humans never win physical competitions with microbes, but sometimes we have spectacular triumphs! Take running, for example. The fastest human achieved a top speed of around 27 miles per hour (44 kilometers per hour). This is 300,000,000 times faster than Chloroflexus, which uses a “gliding motility” to stroll at 0.04 microns per second (0.00000009 mph) and 6,750 times faster than microbes with flagella, at 200 microns per second (0.004 mph).
Closing Thoughts
I love microscopic life, regardless of whether it’s a bacterium, virus, or parasite. They do many absolutely amazing things, oftentimes better or more excessively than humans – we could never take a 101 million year-long nap and wake up feeling refreshed – but being human has its own rewards. We get to enjoy studying and thinking about microbes, but they really can’t spend much time thinking about us. Or can they?
John Warhol is the author of Dr Warhol’s Periodic Table of Microbes, The Small Guide to Small Things, available on Amazon at this link: https://tinyurl.com/Warhol-Small-Guide