ORIGIN AND DISCOVERY

Life on Earth began early in our planet's history with microscopic organisms, or microbes. Microbial life has since shaped our atmosphere, our geology, and the energy cycles of all ecosystems. A human body contains ten times as many microbes as it does human cells, including numerous tiny bacteria on the skin and in the digestive tract. Throughout history, humans have had a hidden partnership with microbes ranging from food production and preservation to mining for precious minerals. Yet throughout most of our history, humans were unaware that microbes even existed. To study these unseen organisms required a microscope, first developed in the 1600s. In the nineteenth century the "golden age" of microbiology microscopes revealed the tiny organisms at work in our bodies and in our ecosystems. The twentieth century saw the rise of microbes as the engines of biotechnology. Microbial discoveries led to recombinant DNA and revealed the secrets of the first sequenced genomes.         In 2008, the Phoenix Mars lander arrived at the north pole of the planet Mars (Fig. 1.1). The lander carried scientific instruments to study the history of water in Martian soil and search for evidence of microbial life. Its robotic instruments tested the soil for life-supporting elements such as carbon, nitrogen, phosphorus, and hydrogen. The discovery of surface water in the form of frost supported the possible existence of living microbes. Why do we care whether microbes exist on Mars? The discovery of life beyond Earth would fundamentally change how we see our place in the universe. The observation of Martian life could yield clues as to the origin of our own biosphere and expand our knowledge of the capabilities of living cells on our own planet. As of this writing, the existence of microbial life on Mars remains unknown, but here on Earth, many terrestrial microbes remain as mysterious as Mars. Barely 0.1% of the microbes in our biosphere can be cultured in the laboratory; even the digestive tract of a newborn infant contains species of bacteria unknown to science. Our "exploration rovers" for microbiology include, for example, new tools of microscopy and the sequencing of microbial DNA. On Earth, the microscope reveals microbes through out our biosphere, from the super heated black smoker vents at the ocean floor to the subzero ice fields of Antarctica. Bacteria such as Escherichia coli live in our intestinal tract, while algae and cyanobacteria turn ponds green (Fig. 1.2). Protists are the predators of the microscopic world. And viruses such as influenza virus cause disease, as do many bacteria and protists. Yet before microscopes were developed in the seventeenth century, we humans were unaware of the unseen living organisms that surround us, that float in the air we breathe and the water we drink, and that inhabit our own bodies. Microbes generate the very air we breathe, including nitrogen gas and much of the oxygen and carbon dioxide. They fix nitrogen for plants, and they make vitamins, such as vitamin B12. In the ocean, microbes produce biomass for the food web that feeds the fish we eat; and microbes consume toxic wastes such as oil from the Deepwater Horizon spill in 2010. At the same time, virulent pathogens take our lives. Despite all the advances of modern medicine and public health, microbial disease remains the number one cause of human mortality. history of fresh news on ORIGIN AND DISCOVERY In the twentieth century, the science of microbiology exploded with discoveries, creating entire new fields such as genetic engineering. The promise and pitfalls were dramatized by Michael Crichton's best selling science fiction novel and film The Andromeda Strain (1969; filmed in 1971). In The Andromeda Strain, scientists at a top-secret laboratory race to identify a deadly pathogen from outer space or perhaps from a biowarfare lab (Fig. 13A). The film prophetically depicts the computerization of medical research, as well as the emergence of pathogens, such as the human immunodeficiency virus (HIV), that can yet defeat the efforts of advanced science.
       Today, we discover surprising new kinds of microbes deep underground and in places previously thought uninhabitable, such as the hot springs of Yellowstone National Park (Fig. 1.3B). These microbes shape our biosphere and provide new tools that impact human society. For example, the use of heat-stable bacterial DNA polymerase (a DNA-replicating enzyme) in a technique called the polymerase chain reaction (PCR) allows us to detect minute amounts of DNA in traces of blood or fossil bone. Microbial technologies led us from the discovery of the double helix to the sequence of the human genome, the total genetic information that defines our species. In Chapter 1, we introduce the concept of a microbe and the question of how microbial life originated. We then survey the history of human discovery of the role microbes play in disease and in our ecosystems. Finally, we address the exciting century of molecular microbiology, in which microbial genetics and genomics have transformed the face of modern biology and medicine.