Crystal 2007

Tom Curtis, School of Civil Engineering and Geosciences, University of Newcastle upon Tyne, UK The microbial world is not really a good expression. It is not a world, it’s not a planet, or a constellation. It’s not even a universe, for there are 1 000 000 000 times more bacteria in the world than stars in the sky. Imagine the microbial ‘world’ as billion universes each made of thousands or millions of galaxies and you have some idea of the scale of the challenge of microbial ecology. Remarkably new galaxies arise constantly. Every time a child is born, a seedling germinates, or a leaf falls, microbes find their place, grow and reproduce with clockwork like reliability, actually a lot better than clockwork. No one would seek to understand the universe star by star. However, it sometimes seems that microbiologists are trying to understand the microbial world one cell at a time. Of course every cell and (each star) is fascinating in its own right and there is tremendous satisfaction to be gained from their study. But these simple pleasures will not be enough. Microbiology is going to develop a body of theory. By theory I mean a consilient (Wilson, 1998) and calibrated set of rules to describe and predict the behaviour of the microbial world as a system. Why theory? Most microbial systems are large and complex and operate at scales that are difficult to observe and, almost certainly, defy intuition alone, which is why we need to seek and quantitatively express those rules. However, our current modus operandi is one of description with ever more sophisticated tools. The tools are telling us that the microbial world is very complex. Though we talk of opening the black box we find we are peeling the black onion. For each innovation reveals more wonders. One has to question whether we as a community can really carry on being surprised by this. We really need to sit down and take stock. There is simply no reason to assume that we can gain an adequate understanding by the unguided opportunistic ingenuity we employ today. We can use these tools to test those putative rules and we can use those putative rules to determine what those tools need to be able to do. We also need theory because the microbial world is of profound practical importance. Agronomists, medical practitioners and engineers want to exploit microbes to cure, clean and grow food. We currently do this empirically, but empiricism is subject to the law of diminishing returns and the insights empiricism delivers are often qualitative and situation bound. Practitioners need numbers. It is one thing to infer the action of gravity and determine that you would need a big rocket to escape the Earth’s pull. It is another to determine the escape velocity and so rationally design a spacecraft. The link with practice is important. Microbial ecology is going to become ‘big science’ and need big budgets. If theory can effectively link the basic science with the economy and national it will us to justify those big budgets. If we do not make that link, I suggest that the money might stop. Clearly political and scientific drivers make the development of theory imperative: it has to happen. How theory? The complex nature of the microbial world may make theoretical descriptions seem impossible. But they are not. For progress will be made using simple ideas, refined iteratively and grounded in truth. Simple truths about a system will describe some part of it. A calibrated model describing that part is a foundation that we can build on and form at least a partial basis for prediction. This may sound like motherhood and apple pie: it ain’t. Truth in this context means parameters and verification. These are hard slog and could require all the ingenuity that modern microbial ecology can muster. But it will be worth it. If we do it we will intellectually outstrip much contemporary classical theoretical ecology. This field is hidebound by the difficulty of experimentation and is therefore contaminated by self-congratulatory mathematical castles in the air with invented parameters and little verification. More importantly calibrated theory will open the door to a new age in microbial ecology as we stop merely gawping at the wonder of it all, like prerenaissance peasants on a star lit night, and start to begin to truly understand.