Significance
We’ve now come full-circle in our walk among Lassen’s hot spring life. We began our journey by asking why scientists bothered to delve into such hostile and apparently isolated corners of earth’s biosphere and what connection the seemingly obscure and undeniably minuscule residents of a volcanic pool have with the world that we live in. The path we have chosen has broadened our view to encompass the large-scale geologic forces that create a hydrothermal habitat; we’ve swept through time to trace the evolution of life on earth and to nest extremophile microorganisms onto their own branches on the Tree of Life. From lofty heights, we traced the flow of energy from the sun and the earth’s interior through intricate metabolic cycles and admired the ecological network that binds together each living resident. Diving down to the realm of a single-cell, we marveled at the ingenious adaptations each thermoacidophile employs to counter the problems of hot springs living. And finally, at the tiniest scale, we examined the DNA molecule, shared by every living being, whose properties scientists now utilize to understand the otherwise inscrutable world of our most distant relatives. Enriched by these far flung investigations, it is time again to ask what significance we can find amidst life in boiling acid.
Significance, like quantum states and art, exists on multiple levels and changes relative to the observer. For the pragmatically minded, microorganisms represent a powerful tool for improving human lives. The growing number of patents on extremophile genomes clearly points to the commercial and economic value of Lassen’s hot spring residents. With new applications in the industrial, environmental and biomedical fields, the impact that these organisms will have on society seems to stretch further and further across the humankind’s horizon.
Beyond PCR
As noted in the introduction, extremophiles form the basis for a host of current technological applications. From detergent proteases to PCR, extremophile enzymes already make up a multi-billion dollar per year industry. But far from exhausting their potential, each advance in biotechnology builds on previous techniques and points to the way toward further possibilities. Consider an example of this momentum-building from the industrial sector: large-scale paper manufacturing is responsible for hydrogen peroxide and chlorine contamination of ground water as a result of traditional bleaching processes. A class of thermo-stable enzymes, called xylanases, reduces considerably the amount of these pollutants required, making the bleaching process more environmentally friendly. But the story does not end there. Recent research into the thermophile Thermus brockianus has yielded a protein capable of breaking down hydrogen peroxide itself. Lab studies have shown that the enzyme lasts up to 80,000x longer than commercial catalysts currently used and that wastewater requires no additional treatment.
As well as improving current techniques, extremophiles may help rehabilitate environments where less progressive methods have already taken their toll. Recently, researchers have used recombinant DNA techniques (discussed in the previous chapter) on extremophilic bacteria, creating a strain capable of cleaning up radioactive waste sites. Deinococcus radiodurans naturally resists the deleterious effects of radioactivity. By coupling this resistance to the expression of enzymes that oxidize a variety of organic pollutants, researchers have engineered a biological tool with the ability to operate in the some of the most degraded and dangerous environments left in the wake of progress.
The medical industry as well awaits the future of extremophile research with anticipation. The discovery of new antibiotics has steadily tapered off in the last few decades and an increasing number of pathogens display resistance to multiple treatments. This potential crisis has forced researchers to probe unexplored sources for novel drugs. Environmental studies using culture-independent methods have shown that less than one percent of the organisms in extreme environments have been characterized, representing an tremendous untapped resource in the search for naturally occurring weapons in the fight against disease. By creating vast clone libraries and examining the products of newly discovered organisms, mankind may reap the benefits of nature’s nearly limitless creativity.
The Bright Light of Science
For science and for the human spirit, significance goes beyond mere utility. Science is not technology, and our interest in the living world is not limited to the ways we can use nature to suit our own needs. For some, the significance of Lassen’s microbes lies in their ability to answer our curiosity about the ongoing evolution, diversity and interrelatedness of life. From the moment humankind began to ask questions about their biological surroundings, we have steadily drawn back the veils that hide the story of life on earth. Now, with thermophilic microorganisms pointing towards our universal common ancestor, displaying unimagined cellular adaptations and giving us glimpses of their distinctive ecosystems, our understanding of the living planet is taking a great leap forward.
It is difficult to imagine now, but the universal Tree of Life was only recently revised to include the domain Archaea as a fundamentally unique grouping. Without the sampling of the extreme environments, like the ones before you in LVNP, our picture of cellular life would have remained hopelessly incomplete. What other surprises await us in the depths of the volcanic pools? Perhaps an environmental sample awaiting genetic sequencing from these very waters will announce the next shift in our collective understanding of evolutionary relationships, and our Tree of Life will once again sprout another branch. Through the lens of earth’s biological diversity, ongoing microbial discovery is at least as significant as the description of new animals and plants.
In the realm of physiology and cellular adaptation, hot springs are issuing answers to questions no one had even though to ask until recently. Through functional gene studies and microbial genomics, we can now examine what kind of tools a microorganism must carry to reduce sulfate at searing temperatures or to carry out electron transport in extreme acidity. If one of the over-arching themes in biology is adaptation to a diversity of environments, then thermal springs are the ultimate proving grounds. Life has shown itself competent to overcome the challenges of nearly any conceivable habitat: here in this steaming volcanic landscape, we can begin to ask how.
Microbial ecology, as well, if not in its infancy, is still in the midst of a precocial childhood. Scientists are only now taking role in hydrothermal environments- full appreciation of the complexity of these ecosystems is a still dream of the future. We regularly describe the macrobiotic world in terms of relationship and interdependence: our understanding of a moth does not stop at a single organism- we seek out the flower from which it receives nectar, the bat that preys upon it, even the parasites that attack its pupae. Species do not exist in a vacuum and full recognition of an organism depends on our grasp of its ecological matrix. But the microecology of extreme environments has so far yielded only shadowy glimpses of the relationships among its residents. Genetic studies have distinguished a number of organisms and have established a handful of their metabolic processes, but our current understanding is a single candle in a very large room. In hot springs ecosystems, as in the world at-large, only the context of relationship will illuminate the larger patterns at work.
An Unfolding
Perhaps one last level of significance remains to the most sensitive of visitors. So far we have explored the living waters of Lassen’s hot springs as detached and remote observers. Is it possible that extremophile microbes can tell us anything about ourselves?
The story of life on earth has unfolded like a immeasurably vast and elaborate flower. By carefully peeling back its rich and beautiful structure we have come to the innermost petals; in the volcanic springs we can appreciate the scope of life’s extravagant multiplicity. This is the miracle of reflection: even as we ponder the distance between bacterium and biologist, we recognize ourselves as another petal in this same epic unfolding.
Thus, for those that can step outside the prejudices of human-centered thought, who can drop the biases of mammal, oxygen-breather and eukaryote, for someone that can rise above the notion that nature has conspired only to create human life, Lassen’s extremophiles are a lesson in perspective. Microbes are not an afterthought of evolution or a side story to the human experience. They represent long standing traditions in an unbroken story of which we are only the latest episode. Far from marginalizing our existence or diminishing the wonder of human life, this perspective welcomes us into a drama far richer than that of mere human history. For those willing to experience it, a walk among our most distant relatives is a chance to see ourselves within the dance of creation.
Our tour of life in Lassen Volcanic National Park has finished: