Book ReviewLarissa Tetsch
John L. Ingraham:
Kin: How We Came to Know Our Microbe Relatives
Hardcover: 304 pages
Publisher: Harvard University Press; 1 edition (26 May 2017)
Human beings have always been fascinated by their origins. In recent decades, modern biology has disentangled the relationship between all organisms, revealing our kinship with microbes and tracing life back to its roots.
Siddhartha Mukherjee during a lecture at Columbia University. Photo: Columbia University
Since Darwin, many attempts have been made to trace the path of evolution and to disentangle kinship among all living beings. For a long time, such studies were solely based on morphological parameters, which, for unicellular organisms, were limited to size and shape. This confinement made taxonomy almost entirely impossible in the bacterial world, with its cells all looking largely the same under a light microscope. Even after the development of electron microscopy, which enabled fascinating insights into the cells of “higher” multicellular organisms, today known as eukaryotes, bacterial cells – due to their density – remained elusive. Consequently, the strikingly different cellular organisation of prokaryotes in comparison to eukaryotes remained concealed.
The seminal discovery of a second group of prokaryotes, indistinguishable from bacteria by morphology but differing vastly in their genetic organisation and other molecular traits, was thus completely unexpected and shook the scientific society. It was only after the dawn of a molecular era, which made single biomolecules susceptible to analysis, that Carl Woese was able to reveal the archaea as a third domain of life, next to bacteria and eukarya. A prerequisite for his work was Linus Pauling’s description of “semantides”, biomolecules that conserve information about their evolutional relationship within their sequence, such as DNA, RNA and proteins. As a second step, Woese had to develop methods to track differences in the sequences that he wanted to compare. At first, he used partial digestion, yielding a species-specific digestion pattern, and later turned to determining RNA and DNA sequences directly using Fred Sanger’s dideoxy (or chain termination) method. Today, comparing the sequence of ribosomal RNA genes is the most widely used method for kinship analyses.
Parts of the scientific community were, nevertheless, reluctant to accept the consequence of Woese’s finding that bacteria and archaea, although prokaryotes in their cellular organisation, are evolutionarily as distinct from each other as they are from all eukaryotic organisms, including ourselves. Even nowadays, the debate continues and some researchers propose the expulsion of the term ‘prokaryote’ from the scientific language, because, in their opinion, it blurs the substantial differences between bacteria and archaea.
In Kin, John Ingraham, Professor Emeritus at the University of California in Davis and former President of the American Society of Microbiology, describes the milestones on the way to Woese’s pioneering discovery. The book consists of two main and a shorter third part. In the first section, Ingraham retraces the discovery of the Tree of Life. The second section elaborates on common problems in determining evolutionary relationships between organisms that make frequent use of horizontal gene transfer to acquire new traits, like prokaryotes do. Despite this fact, a bacterial species’ core genome remains fairly constant and thus can be used for relationship studies, as Ingraham argues. The third concluding part presents a short outlook – or rather retrospect – on how life might have emerged.
Concurrently, the author provides sort of a Who’s Who of molecular and microbiology by portraying the scientific protagonists, not only with their skills and talents but also with their shortcomings. The reader learns that Woese had a notorious need for recognition and suffered from a subjective rejection of earlier results by his peers. Probably due to this fact, he launched a press conference prior to publication of the archaea’s discovery – a fatal decision, which prompted sensational media coverage and seems to have been more harmful than helpful to Woese’s scientific reputation. Ingraham speculates that this press conference and its consequences might have been one reason, why Woese was never awarded with a Nobel Prize, despite his undisputed achievements.
Notably, it is the many side stories about well-known, lesser-known and underestimated researchers, their conflicts and personal tragedies as well as the role of coincidences in science that make the book diverting and worth reading. For instance, Ingraham explains why Francis Crick and James Watson solved the structure of the DNA double helix instead of Linus Pauling, who seemed to be more likely to achieve this goal. But for political reasons, the double Nobel Prize winner was not allowed to leave the United States and was, therefore, unable to travel to England to discuss results with Rosalind Franklin.
Furthermore, the reader learns that Joshua Lederberg’s Nobel Prize hung from the slim thread of his co-researcher Edward Tatum, who provided the former with E. coli K12, a strain that, in contrast to the more commonly used strain E. coli B,was capable of transduction – and some more intriguing anecdotes on famous life scientists and their startling discoveries.
On the whole, Kin is overflowing with information and provides even molecular biologists, who are familiar with the scientific facts, with enough inside stories to entertain.
Letzte Änderungen: 01.10.2017