Life’s Engines: How Microbes Made Earth Habitable
by Paul G. Falkowski
Princeton University Press, Princeton, NJ, 2015
224 pp., illus., 38 b/w. Trade, $24.95
Reviewed by Cecilia Wong
Independent writer, Los Angeles
Web address: Eyes-wide.com
Scientists are currently working in earnest to find a process to split water -H2O-a difficult task because its hydrogen and oxygen atoms are held together with a great deal of energy. Researchers hope that releasing that energy could provide a plentiful green fuel. But the photosynthetic cyanobacteria, a precursor to chloroplasts in plants today, have been splitting water for more than 2.4 billion years using light from the Sun. Paul Falkowski’s timely book tells that enthralling story of how this and other life’s core nano-engines made way for plants and animals to evolve and continue to hold our Earth in a dynamic and fragile balance. The first simple animals appeared in the ocean only 580 million years ago, and it was a rapid trip from microbes to us humans - this book explains how open and unstable our genes and DNA molecules really are to allow for such fast evolution to occur - all thanks to these nano-machines in promiscuous microbes.
Life’s Engines is a science book that approaches art in story-telling-fascinating, fast and fluent: one discovery leads to another question and another experiment - it reads like a thriller, except the subject is our own survival. Each chapter is a mini lecture on personal discoveries set in the context of history of science. Why Darwin puzzled over the sophistication of our vision as possible refutation of his theory: Could only God have invented eyes? Even Samuel Pepys, the famous 17th century English diarist, makes an appearance-commenting on the first best-selling science book in history: Robert Hooke’s Micrographia (1665). And the microscope Hooke used only came about because Galileo had turned his telescope to look from the other end…Also, the singularity of these core nano-machines - they only evolved once in our extinct ancestor- answers Darwin’s dilemma: did life come from a single origin?
Darwin’s 1859 theory is based on observable body forms. At the turn of the 21st century, rightly called the century of chemistry, Falkowski is proposing to construct an alternative evolutionary tree: one based on the chemical structure and interactions in life’s essential nano-machines. The heart of the book is the production and exchange of energy in the infinite number and variety of microbes, and how they are more powerful than humans in shaping our Earth.
The author intended this book for the common reader for whom microbes are out of sight, out of mind - but we ignore them at our own peril. Thus a due caution: the chemistry in this book is not for the faint-hearted among us. Falkowski’s engaging arguments assume a solid grounding in chemistry and physics, sometimes as if he’s conversing with his colleagues; though the clear focus and logic carry the reader through.
At the foundation of all life is the process of capturing the Sun’s energy, storing it in the cell for a rainy day-photosynthesis; and respiration-release of that energy for growth and reproduction. Chemically, in respiration oxidation occurs when oxygen accepts an electron from the hydrogen in sugar, producing carbon dioxide and water as waste products, along with energy. Reduction is the reverse, when sugar molecules are formed from photosynthesis. Respiration occurs in another nano-machine in our cells: the mitochondria.
Electrons are the currency of exchange in what Falkowski calls the “electron marketplace” among microbes. They live close to each other in groups, one using the waste product of another, trading electrons. They also exchange genetic materials freely, sometimes engulfing another to capture their nano-machines. This horizontal gene transfer is far more frequent and rapid than vertical transfer in reproduction. The microbial community is what the author calls life’s “research and development department”-what works lives, others die.
Earth’s Great Oxygenation Event around 2.4 billion years ago was caused by cyanobacteria, and paved the way for larger life-forms like plants and animals today. It also caused cycles of glaciation (Snow Ball Earth) and mass extinction. Falkowski warns against artificial microbes (synthetic biology) in our haste to produce more energy: once unleashed these self-replicating machines could again make our Earth uninhabitable by changing the atmospheric gases.
On a personal level, our microbiome, the microbes living with us in our body: skin, mouth, hair, gut… number ten time more than our own body cells-with more genetic material than our own DNA. Many have become linked to our body metabolism - it’s to a parasite’s advantage to help its host live - and killing them often disturbs our own health in subtle ways. There is evidence that our indiscriminate use of antibiotics has led to many modern diseases from obesity to autism to allergies. Worse, microbes fight back by becoming more virulent in a vicious cycle.
So how long can we continue to treat the Earth and its microbes, to which we owe our existence, as enemy and spoils?Falkowski asks:
“Human knowledge, which is acquired and disseminated globally by horizontal information transfer, has clearly been extremely effective in helping humans temporarily control the planet… Will microbes become increasingly resistant to our most advanced antibiotics and once again be able to kill us en masse?”