# The Journey from a Bacterium to Revolutionary Genetics Discoveries
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Chapter 1: The Quest Begins
In 1994, a Swiss biologist named Pascal Gagneux embarked on a Ph.D. program in zoology, focusing on the wild chimpanzees of Cote d’Ivoire and Mali. His aim was to locate chimp nests in forest trees. Once he pinpointed their sleeping spots, he would wait until the chimps left to search for food, allowing him to collect hair samples from their nests.
Gagneux sought to document the genetic diversity among these critically endangered primates. He needed to extract DNA from the collected hair follicles and amplify it quickly. Had he pursued this research a few years earlier, this crucial amplification step wouldn’t have been feasible. However, thanks to a revolutionary scientific method and a serendipitous discovery in Yellowstone National Park, Gagneux found that chimpanzees exhibit far greater genetic diversity than humans. “There’s more diversity in one social group of chimpanzees than in all 7 billion humans on the planet,” he noted.
The polymerase chain reaction (PCR), a technique introduced in 1983, enabled scientists to replicate a single DNA fragment into numerous copies. This method proved critical for Gagneux's research, as it allowed for the exploration of genetic diversity in an era when the wild chimp population was rapidly declining.
Section 1.1: The Birth of PCR
PCR is often regarded as one of the most significant technical breakthroughs in modern science. This method has been instrumental in various applications, from identifying previously unknown bacteria responsible for severe Lyme disease to assisting medical professionals in screening for hereditary conditions such as Tay-Sachs and cystic fibrosis. Kary Mullis, the inventor of PCR, was awarded the Nobel Prize in Chemistry in 1993 for his groundbreaking work.
The roots of PCR can be traced back to the mid-1960s when researchers discovered a unique pinkish-orange bacterium in Yellowstone's hot springs. This chance finding was not driven by the desire to advance DNA replication techniques; rather, it stemmed from pure curiosity that ultimately transformed the field of genetics.
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Section 1.2: Discovering Thermus aquaticus
In the mid-1960s, Hudson Freeze, then an undergraduate at Indiana University, attended a lecture by Thomas Brock, who was investigating microbial ecology. Brock was particularly interested in how photosynthetic microbes functioned outside lab conditions, especially in hot springs with stable temperature ranges.
In the summer of 1966, supported by a National Science Foundation grant, Brock and Freeze ventured to Yellowstone to collect samples of bacteria thriving in hot springs. While examining a sample at an astonishing temperature of 176 degrees Fahrenheit (80 degrees Celsius), Freeze discovered the pink filaments of a previously unknown bacterium, which Brock later named Thermus aquaticus, meaning "hot water."
Despite the excitement surrounding this discovery, Freeze initially viewed the bacterium as an interesting curiosity with little practical application. However, its potential would later revolutionize genetics.
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Chapter 2: Transforming Science
As the 1980s unfolded, researchers were eager to find efficient ways to replicate DNA. In forensic science, for example, a tiny blood sample left at a crime scene might not provide sufficient DNA for analysis. However, if scientists could amplify that DNA into numerous copies, it would become viable for testing.
The PCR process, although not reliant solely on T. aquaticus, requires a specific enzyme called polymerase. By mixing the target DNA with polymerase and nucleotides, and subjecting the mixture to cycles of heating and cooling, researchers could exponentially multiply DNA samples. This process allows one DNA strand to become millions in just hours.
The early methods of PCR were cumbersome. Initially, the heat would deactivate the polymerase, necessitating the addition of more enzyme at every cycle, which proved labor-intensive. Mullis and his team sought a polymerase that could withstand high temperatures and eventually found it in the T. aquaticus strain. This discovery solidified the bacterium's place in scientific history, leading Science magazine to name its polymerase "Molecule of the Year" in 1989.
The rights to the PCR technique were sold for around $300 million, yet T. aquaticus itself remained unpatented. Most researchers in foundational sciences do not aim for financial gain; their priority is advancing knowledge and sharing it with the scientific community.
Today, Freeze serves as the director of the human genetics program at the Sanford Burnham Prebys Medical Discovery Institute in California, utilizing PCR in his daily work. He finds profound meaning in his contributions to science, stating, “Here I am using the fruits of this discovery and I’m actually improving lives with it.”
Gagneux, who now works alongside Freeze, expressed his surprise upon discovering the significance of Freeze’s earlier work. This highlights a common theme in basic science: it often goes unrecognized, even as it plays a crucial role in groundbreaking advancements.
In 2014, during a family trip to Yellowstone, Gagneux sought out the hot spring where T. aquaticus was discovered. Although the area was striking and vibrant, there was no signage to commemorate its historical significance. Gagneux reflected, “I was happy to think I saw that pool. I sent Hud an email and told him, ‘I think I found it.’”
Maggie Koerth-Baker is the senior science reporter at FiveThirtyEight.com, with her work featured in prominent publications such as The New York Times Magazine and The Atlantic. This article was commissioned by the Science Philanthropy Alliance as part of its Science to Society series, emphasizing the critical role of basic scientific research.