DeathValleyNP
This is the official tumblr of Death Valley National ParkINVISIBLE LIFE
We are Oliver Goodman, Alexa Boesel, and Fred Cohan from Wesleyan University, and here is our next story for Invisible Life!
We all know Death Valley’s Badwater Basin to be a harsh place, covered with a thick layer of salty sediments. What might this salt flat have to do with preserving life?
It would seem not much, until you dig deeper, almost 200 meters. In the 1990’s Tim Lowenstein and colleagues dug a narrow hole that was 186 meters deep and 10 centimeters (4 inches) wide, in the Badwater Basin. The “core” they extracted contained layer after layer of salty and muddy sediments dating back over the last 200,000 years, yielding the history of the Badwater Basin.
Diving into the top (most recently deposited) 90 meters of the core, Brian Schubert and a team of geologists and biologists found that the ancient salt rocks contained small fluid centers (or inclusions), and within these inclusions they found dead microbes going back 100,000 years. Even more exciting, they discovered that some of these intensely salty fluid inclusions had preserved live microbes for as long as 22,000-34,000 years! Upon release from this saline fluid, the cells were still functioning!
As they sampled the core, Schubert and colleagues uncovered stratified saline layers of ancient permanent and temporary lake ecosystems, as well as mud flats and salt pans, over different times. The live cells all came from the salt rock remains of a perennial saline lake that covered Badwater 22,000-34,000 years ago. Aquatic saline environments from other epochs were less likely to create the necessary conditions for keeping cells alive.
As we mentioned in the beginning of Invisible Life, there are many types of microorganisms. There are prokaryotes, such as Archaea and Bacteria, as well as eukaryotic microorganisms, but prokaryotes are much more successful in extreme environments (for example, those with lots of salt). Indeed, the ancient living cells retrieved by Schubert and colleagues were all members of the Archaea. It is much less likely that we would ever find a 34,000-year-old eukaryotic cell within a salt crystal. While the fluid inclusions within rock salt may not be the key to human, or even eukaryotic, preservation of life, they provide a fascinating record of life! Within just 90 meters of soil depth, scientists can observe prokaryotic evolution through various environmental conditions over at least 100,000 years, all preserved within the soil layers. It is prokaryotic paleontology! (lh)
Further reading:
http://schubertlab.weebly.com/uploads/1/6/8/3/16833266/schubert_et_al_2010_env_microbiol.pdf
Photo credit (top): Schubert: Mike Timofeeff (bottoom) Bernard P. Friel
We are Alexa Boesel, Oliver Goodman, and Fred Cohan from Wesleyan University, and here is our next story for Invisible Life!
These are exhilarating days for the discovery of bacterial diversity, much like an earlier golden age of biological discovery two centuries ago. In the early 1800’s, European naturalists traveled the globe in search of unknown creatures, while today, we are finding even more wildly foreign species! The earlier explorers found animals and plants that had never before been seen by western scientists, but many of these creatures were regularly observed by other humans and even had local names. The Europeans were just the first to create scientific records of them! Moreover, many of the exotic creatures were living in habitats similar to those already known, and explorers were simply finding new organisms performing old tricks. For example, Charles Darwin found finches on the Galapagos Islands that ate the normal finch diet of seeds, but he also found strange finches with unfinchlike diets of insects and fruits, foods consumed elsewhere by birds such as warblers, woodpeckers, and toucans. In contrast, today’s explorers of microbial diversity are discovering extreme conditions in which life can succeed, often teeming with organisms that are utterly disparate from any known creature.
Fred and his colleagues Rob Dungan and Jong-Shik Kim, along with their students, were interested in exploring the bacterial diversity in the extreme habitat underlying the salt crust near Badwater. Were there any creatures never before seen by science? Rob carefully scraped away the surface evaporite layer (containing the salt crystals), and sampled the underlying wet sediment which, unsurprisingly, was extremely salty.
Since only a small fraction of a bacterial community’s diversity is readily cultivable in the lab, scientists need to characterize a community’s inhabitants without the benefit of growing the organisms. So, Jong-Shik and his group extracted DNA from the community samples and obtained DNA sequences of a particular gene (called 16SrRNA, and shared by all cellular life). When comparing the DNA sequences to all known sequences, we found that we had discovered many new species, as well as a half-dozen new genera! (“Genera” is the plural of genus.) What does it mean to discover a new genus? It would be like scientists had never noticed that there were oak trees in our forests (the 600 species of oaks comprise the genus Quercus), and all of a sudden the oaks that had been invisible to us became apparent. How will the new bacterial genera contribute to their saline environment?
Cultivation-free approaches based on DNA sequencing have led to discovery of bacterial groups that are vastly different from any cultivated organism—beyond new genera, microbiologists are finding new families, new classes, and even new phyla (the most grossly disparate groups of bacteria). Since scientists began using cultivation-free approaches to discover bacteria 25 years ago, there has been no slow-down in the rate of discovery. There is so much more to be discovered and so many more extreme ecosystems to be explored!
Photo Credit: April Leytem
Further reading:
Mining Death Valley
For
more than a century and a half, people have looked lustily at Death Valley as a
land of riches. Prospectors have sought
minerals from gold to silver to talc to borax in our hills…and found them all. Photo credit: J. Shafer
Since
the National Park Service began managing the valley in 1933, however, mining
activity slowed and eventually stopped in the interest of maintaining the land
here in what has been described as a more natural condition. But as miners departed, they left a lot of
their equipment and the holes they’d dug with it behind. Photo credit J. Shafer
Today,
visitors travel to these mine sites in search of other riches. Some appreciate being in places where other
people have been. Others enjoy mines’
ability to communicate technical and geologic information. Still others see icons of the old west or
rusting equipment as aesthetic assets in their own right. If you were to travel to these sites, what
riches would you look to mine from them? Photo credit: J. Shafer
How do you think they impact the valley’s value as a preserve of natural space? How can mines help us understand how other people interpreted Death Valley’s wealth? How would the valley be changed if every old mine shaft and tool were removed from it? Photo credit: J. Shafer
We are Alexa Boesel, Oliver Goodman, and Fred Cohan from Wesleyan University, and here is our next story for Invisible Life!
Mesquite Flats, an extreme environment just south of the Cottonwood Mountains in Death Valley National Park, comprises hundreds of towering sand dunes. In addition to being a site for the filming of George Lucas’s Star Wars, Mesquite Flats is where our very own laboratory has collected Bacillus bacteria that we have used in studies of evolution. A recent study by Eric Prestel and colleagues finds that species diversity in extreme environments like Death Valley’s Mesquite Flats is vast—much more so than we ever thought possible.
But what exactly does live at Mesquite Flats?
Bacteria and viruses live here, yet “live” might be too strong a word in the case of viruses. Many scientists debate whether or not viruses are biotic (living) or abiotic (not living) because they do not have cellular mechanisms of their own. Instead, they co-opt the physiology of their host cell. Nevertheless, we note that viruses reproduce, they undergo mutation, they are subject to natural selection and evolve, they consume resources, and they compete with one other; so for our purposes viruses have all the essential features of life, and we will consider them subcellular, living creatures!
While we understand genome replication in many viruses, we know very little about viral genome composition and DNA sequences. In fact, 36% of the viral DNA found in Mesquite Flats was completely unknown. We are increasingly finding that viral DNA may be more diverse than even that of bacteria.
Yet it is not just sequence diversity that makes viruses interesting; it is also that they exist passively in most bacterial cells! When sampling Mesquite Flats soils, the Prestel group found that 84% of bacteria contained at least one viral genome inserted in a passive state into the bacterial genome, where they may remain dormant for many generations; under the right circumstances, these passive viruses can become induced to become active and kill their hosts.
The viruses (or phages) that attack bacteria show promise for helping us in our war against bacterial pathogens, especially those that have become resistant to standard antibiotics. In the petri dish photo, Graham Hatfull and co-workers plated one strain of Mycobacterium (related to the bacteria that cause tuberculosis) together with random viruses collected from nature. Each circular hole in the bacterial growth represents the attack of a different virus against the target bacterial strain. Experiments like this convince scientists that there are hundreds of natural viruses that can kill any given bacterial pathogen that is attacking our bodies, and they are working toward developing phage therapy as an alternative to antibiotic therapy.
Was phage therapy predicted by Jonathan Swift in the 18th century (as amended by Ogden Nash)?
Big fleas have little fleas,
Upon their backs to bite ‘em,
And little fleas have lesser fleas,
and so, ad infinitum.
Further reading:
The Damage of Off Road Driving
The Ibex sand dunes are an ecosystem for many species. Plants and reptile like the Mojave fringed-toed lizard call these dunes home. It is the only place in Death Valley National Park where you can actually see this lizard species. It is a place we desire you to visit, explore and enjoy. However vehicles in the park are not allowed off road. Off road driving is prohibited in the park. This means stay on paved and dirt roads. Damage to these dunes creates many issues for our wildlife plus takes from our limited manpower resource to restore wilderness back to its natural habitat. You are destroying the habitat of the Mojave Fringed-toed lizard. It buries itself in the sand and vehicles driving on the dunes can unknowingly run over it as well as plant species that grow on the dunes. Thanks to the AmeriCorps youth and Charlie our wilderness coordinator who worked tirelessly to get these tracks removed.
photo by Birgitta Jansen
photo by Birgitta Jansen
AmeriCorps crew raking out tire tracks in wilderness area near Ibex sand dunes
Off Road Driving is Prohibited in Death Valley whether it is a paved or dirt road. Hiking is allowed.