Small but perfectly formed

Degrees of Freedom - Life at Small Scale
August 8, 1997

Much of the beauty and fascination of biology lies in the highly complex ways in which organisms have adapted to their environment. The "design" through evolution of both the structure and behaviour of organisms can appear to be more ingenious and imaginative than anything humankind is capable of devising. While most people would think of large animals as the best examples of this, complexity and adaptiveness are not restricted to the macroscopic world, and in Life at Small Scale: The Behavior of Microbes, David Dusenbery gives a fascinating tour of the wonders found in the world of micro-organisms. Rather unconventionally he classifies as microbes all organisms small enough not to need a circulatory system, so including creatures such as flatworms and nematodes not normally studied by microbiologists. This provides a veritable smorgasbord of microscopic bugs and beasties to illustrate the enormous variety of behaviour that is seen in microbes, and the ingenious ways in which they have overcome the problems posed to them by their environment.

The necessary biophysical background is given to allow the reader to appreciate the difference in the problems facing micro-organisms from those faced by larger organisms, such as humans. If one considers just one problem, how to move through water, a bacterium 0.1mm in size and moving at 1mm/sec faces very different problems from a whale ten million times larger and moving a million times faster. The main force opposing the whale's movement is the inertia of the water, yet this is not a factor for the bacterium which, if it stopped swimming, would coast for less than the width of a single atom. The main factor that influences the bacterium is the water's viscosity, and so the design of the organism reflects this; there is no streamlining of its shape and it must rely on mechanisms of propulsion that use the viscosity, rather than the inertia of water, to propel it.

Dusenbery describes, with the help of a large number of stunning photographs and diagrams, the strategies that are adopted by the microbes to move, feed, communicate and learn. The examples are both surprising, fascinating and beautiful. The solutions that these relatively simple organisms have evolved are sometimes akin to the most imaginative Heath Robinson type of invention (though more elegant in their construction). For example the fungus Pilobolus kleinii propels its spores several metres away using a water jet, which accelerates the spores to 10-20 m/sec. Fascinatingly, larvae from the nematode Dictyocaulus viviparus (which causes a parasitic bronchitis in cattle) take advantage of this as a mode of transport by crawling up the stalks of Pilobolus and coiling up on top of the spore mass, waiting for the water jet to propel them onto fresh vegetation that, hopefully, will be eaten by a cow.

It is an exciting and highly enjoyable tour through an area of biology. Clearly the book is not aimed at the professional microbiologist, and at least one previous reviewer has noted that some of the examples have been oversimplified. The details of the biophysics and the experimental background to some of the work may make it slightly heavy going for the lay reader. However, with its beautiful colour photographs it would make an excellent coffee-table book for a scientist willing to be entertained and fascinated by another area of science. It should also be read by sixth-form students, who will have enough science to be able to follow the arguments and descriptions, and who will be inspired by a glimpse into this normally invisible world.

One theme that clearly emerges from the study of these micro-organisms is that the assembly of subunits into larger complex structures introduces additional rules of organisation. As a result, biology is a holistic science. However much reductionist principles are used to dissect out individual components in a system, we still have to put these components back together to see how they function. It is perhaps this necessity to look at the whole organism (and its interactions with its environment) that has led to the championing of new paradigms by Fritjof Capra and others who seek to look at biology in a more holistic and less mechanistic manner. Such approaches also often seek to inform the way in which human society behaves, possibly as a counterbalance to the perceived influence of Darwinian principles on society.

In Degrees of Freedom: Living in Dynamic Boundaries, Alan Rayner throws a new set of ideas into the ring. He draws on a deep knowledge of fungi and a wider understanding of other biological systems to produce a thesis that sees life developing as a consequence of the interplay between association and dissociation at the boundary between a system and its surroundings.

This leads to a concept of indeterminant systems which interact with their surroundings in unpredictable ways, challenging the view of organisms as discrete entities that interact in a predictable manner. The behaviour of such systems can be explained with four "fundamental processes" by which they control the flow of energy across or within boundaries: conversion, regeneration, distribution and recycling. Conversion processes involve sealing and immobilising the boundaries of the system, following assimilation of energy from the external environment, and produces "survival capsules" such as seed and spores.

During distributive phases the boundaries are sealed, but not immobilised. This allows the structure to explore through environments that cannot sustain growth, as energy is not lost across the boundary. Examples include mycelial cords sent by fungi through areas of low nutrition, and the foraging parties of ants. Once the external environment becomes more favourable, regeneration occurs, and open boundaries are formed to allow energy acquisition. This equates to germination, or the formation of settlements following migration. Finally, during recycling, resources are redistributed from parts of the system that are no longer needed, leading to the degeneration of the boundaries of structures.

This book is in turn frustrating, stimulating and opaque. It is wide ranging, and it is perhaps not surprising, though unfortunate, that some of the examples are inaccurate or highly selective. Much of the argument is couched in a turgid style, and is therefore heavy going. In providing a novel description of biological systems the author is seeking to make us see the world in a new light; while this may influence our behaviour (a not inconsequential action), it is difficult to see how it can provide the same predictive power as conventional biology.

The book really comes alive when drawing on the fungal world. Mycology is a relatively obscure field of biology and Rayner is able to surprise us with highly instructive examples of their complex behaviour and structure (for example an individual Armillaria bulbosa fungus is 1,500 years old and weighs 100 tonnes, qualifying as the largest discovered organism). The effect of these descriptions, together with the novel way of looking at biological systems, is to jolt the reader from his/her preconceived notions and provide fresh insights into other aspects of biology. If readers do not allow themselves to be frustrated by other aspects of the book, they may find in it a new and stimulating perspective on their field.

Andrew J. T. George is senior lecturer in immunology, Hammersmith Hospital, London.

Degrees of Freedom: Living in Dynamic Boundaries

Author - Alan D. M. Rayner
ISBN - 1 86094 037 4
Publisher - Imperial College Press
Price - £.00
Pages - 312

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