Connecting Global Priorities Biodiversity and Human Health

Case study: herus auatius and DNA research
Thermus aquaticus is another behind-the-scenes, though absolutely vital, species for biomedical
discovery. This bacterium was rst identied in the Mushroom Spring of ellowstone National Park
in 1966 as part of an expedition to nd life in places where it was not supposed to exist. The late
summer day that Thomas Brock and Hudson Freeze collected samples from Mushroom Spring, the
water temperature measured 69 ºC.
At rst, T. aquaticus was little more than a curiosity: an organism able to live at temperatures that
would cook most cells, including human cells. This reputation soon changed. Advances in the early
years of genetic research were many but were limited in part by diculties with replicating DNA in a
laboratory. All life replicates DNA in order to survive. To do this, paired strands of DNA are separated
and then copied using a specialized molecular copying machine known as DNA polymerase.
To separate the DNA strands, cells use a set of molecular machines. Using these machines in a
laboratory proved too dicult, so scientists turned to another method, heat. DNA strands reliably
separate at temperatures just over 90 ºC and remain separate at around 70 ºC, right near the optimal
temperature for T. aquaticus and its DNA polymerase known as Taq. The ability of Taq to copy DNA at
high temperature forms the foundation of the polymerase chain reaction, or PCR, which is arguably
the single most important tool in genetic research ever invented. In 2013 alone, nearly 27 000
articles make reference to PCR in the US National Library of Medicines PubMed database.
ust as with the ability of natural products obtained from one species to exert inuence on many
others, the ability of Taq to work on DNA from multiple species underscores how all life shares some
basic features. At the same time, Taq also speaks of the importance of the diversity of life. Without life
thriving at high temperatures, there would be no polymerase suitable for PCR and, without PCR, the
modern-day genetic research juggernaut may never have got o the ground.
Source: Brock and Freeze (1969)
3. Biodiversity, the microbiome
and antimicrobial resistance
Far greater than what individual species offer
to medicine through molecules they contain
or traits they possess, an understanding of
biodiversity yields irreplaceable insights into how
life works, which bear upon current epidemic
diseases. Consider the multiple pandemics that
have resulted from antimicrobial or antibiotic
resistance (see also the chapters on infectious
disease and health care and pharmaceuticals in
this volume). Human medicine tends to use a
paradigm for treating infections unknown in
nature, which is treating one pathogen with one
antibiotic. Most multicellular life (and a good
share of single cellular life) produces compounds
with antibiotic properties but never uses them
in isolation. Infections are attacked, or more
often prevented, through the secretion of several
compounds at once.
Antibiotic use, aside from its potential to cultivate
resistance, also carries the potential to disrupt
relationships between hosts and their symbiotic
microbes. The human microbiome contains tenfold
more microorganisms than cells that comprise the
human body, and antibiotic use can dramatically
alter its composition and function (Cho and Blaser
2012). Although much of the microbiome and
its relationship to its host remains unknown, it
is already apparent that changes to the variety
and abundance of various microorganisms,
as can occur with antibiotic use, may affect
everything from the host’s weight and the risk of
contracting autoimmune disease, to susceptibility
Connecting Global Priorities: Biodiversity and Human Health
167