Cells

Size matters, but, according to Nicholas Money, few have comprehended what this really means. For too long we have been entranced by the grandeur of plants and animals that are visible to the naked eye, even when the focus of attention shifts to their DNA or the wider ecological setting. Money wants to direct our gaze towards the little things of life. It is at the microscopic level, he argues, that life comes into its own. In terms of total biomass, microscopic life forms considerably outweigh their larger multi-cellular counterparts.

Small should not be equated with passive. Microorganisms play an unheralded role in running the planet. It is they that control the nutrient flows of the ocean. Huge conglomerations of sea algae can be seen from space as spectacular blooms, stretching for hundreds of miles near the surface of the water. Their fundamental role is one that we will ignore at our peril as climate change threatens to affect all ecosystems from the poles to the equator and from mountaintop to deepseabed.

Microorganisms are present everywhere. Human beings are teeming with them. So are all sources of fresh and salt water, other animals, plants, the soil and the air. As well as the vast array of single-celled organisms, there are also the viruses. These may require a host, a cellular organism, in which to reproduce, but as an entity viruses are extraordinary successful. Money describes them as the most “abundant biological entities on the planet”. This puts a new gloss on the common cold or the near eradication of polio or the not yet so successful battle against HIV/AIDS. One of his unexpected announcements is that most of the planet’s genetic diversity is bound up in these strands of nucleic acid or “molecular organisms”. The figures are astonishing. A millilitre of seawater from the North Atlantic contains 15 million viruses.

“Molecular organism” is one of the easier terms to comprehend. As well as the multitude of species names there are the newish titles of the eight groups of eukaryotes (cellular organisms with nuclei) that have replaced the old-fashioned animals, plants, fungi and protists. It is part of the wider point that Money is making that, unlike in the familiar macro world, few of his featured microorganisms have common names. Those of us of the “Schwarzenegger generation” will enjoy “Conan the Bacterium” (Deinococcus radiodurans) which is able to withstand huge doses of ionizing radiation. Conan and his fellow bacteria have been little studied and even less made the subject of user-friendly popular science.

When the guts’ microbiome loses its natural harmony we suffer

It is to Money’s credit that the book never slips into a dull encyclopedic style. He may have been on his guard against this, having taken a sideswipe at some of the “stamp collecting” natural historians of the past, concerned above all with cataloguing and taxonomy rather than functionality and experiment. Patient observers in the field were vital. A knowledge base is by necessity a cumulative enterprise. The movers and shakers of biology relied on their own observations and those of others to arrive at their more profound discoveries. A look at the Darwin correspondence bears out just how much the great man relied on collectors, pigeon fanciers and market gardeners.

If Money shows impatience with the past, tending to berate people for not knowing what they couldn’t have known, he pays due homage to two technologies that have helped create the present dynamism. The first was the electron microscope. The second is the ever-improving and cheapening techniques of DNA sequencing. These helped liberate microbiology from the need to grow organisms in the laboratory as proof of existence. Shotgun sequencing has allowed mass sampling, so that increasing numbers of organisms are known only by their genetic signature.

What applies to the mass of microorganisms in the soil or water also applies to those that make their homes on and in us. When pathogenic bacteria were discovered to cause disease in the nineteenth century, the body was assumed to be in a pristine state until invaded and rendered sick. The appreciation of healthy carriers shattered such illusions. Now we learn that a single gram of faeces contains 100 million archaea and 40 billion bacteria. When the guts’ microbiome loses its natural harmony we suffer. There is good evidence that allergic and autoimmune diseases occur as a result of sustained imbalances. Even a normal course of antibiotics has persistent negative effects. Foetuses in the womb are unsullied beings, a situation that changes rapidly as they pass through the vagina to emerge into the world. C-section babies miss out on this microbial seasoning and it may well affect their health.

Appropriately, Money makes his readers wait until the sixth of his eight wonderful chapters to bring humans into the picture and he ends with those archaea and bacteria that can live in the most extreme environments. Their ability to use chemicals, rather than sunlight, to power their existence more than hints at the origins of life itself. None of this can be seen unaided, but this should take nothing away from the majesty of the microbial world. If we are prepared to suspend disbelief, Nicholas Money is an expert guide. The world will not seem the same to anyone who reads his book.

Helen Bynum is a freelance writer. She is the co-editor of Great Discoveries in Medicine, 2011, andSpitting Blood: A history of tuberculosis, 2012.