PLM10: the Physics of Living Matter is coming of age

This week, Cambridge (UK) hosted the 10th Symposium on the Physics of Living Matter (PLM10) (http://www.plm-symposium.org/). For those of us who were at PLM1, it is surprising to see that what was (and remains) a grass roots organized event, persists. In some ways it is a tribute and an example that a community can be created by nurturing a common set of interests; in this case how the physical sciences can shed light onto biological problems (NB this is different from Biophysics which looks for biological examples of physical phenomena).

The symposia started with the view of making the local community aware of developments at the interface of Physics and Biology. In the early 00s there were a few pockets of activity cradling this interest. In particular, the legendary Physiology course of Woods Hole (this year’s Bragg lecture was given by Julie Theriot, who has been a pioneer in the field and an active participant in Woods Hole), Eric Karsenti’s division in EMBL, Dresden CBG/PKS was starting and Stan Leibler in Rockefeller was breeding a group of interesting scientists, while individuals like Dennis Bray, were making significant contributions from ‘the side”. Things have changed and ten years on, the interactions between Physics and Biology are on a solid ground. This year’s Symposium bore witness to this and left the message that the future of Biology lies in the quantitative analysis of biological problems and on the use of the reasoning and methods of the physical sciences. It has taken a long time to come but many of us got the feeling at the meeting that the Physics of Living Matter is coming of age.

In his book “What a mad pursuit”, F Crick comments on how Max Delbruck was driven into Biology to search for new Physics to explain living systems (see http://amapress.gen.cam.ac.uk/?p=1489 if you want to learn a bit more) and contrasts this with the belief of Linus Pauling in Chemistry to understand the same problem. Crick makes the point that, as he sees it, history shows that Pauling was right and Delbruck was wrong. However, he puts it in an interesting manner by stating that “time has shown that, SO FAR, Pauling was right and Delbruck was wrong……”. It is the ‘so far’ that reveals Crick’s caution and belief that the story had a second part. This second part is emerging now. With hindsight one can say that the reason why Chemistry rather than Physics provided the insights into Biology during the XX century was, simply, that the problem then was the structure of living matter, not its function. And the structure was, and remains, a problem of Chemistry. Surely one uses physical methods to understand it e.g crystallography and the different flavours of microscopy, but the answers lie in Chemistry. However, when we want to understand how the elements of living matter combine and interact to make WORKING cells, tissues and organs, we have to recur to physics. Herein we find the ways in which biological systems ‘cheat’ the laws of equilibrium thermodynamics and statistical mechanics and, in probing the HOW we learn about how Physics helps explain Biology and about how Biology extends Physics. The XXI century proves that both Pauling and Delbruck were right and PLM10 was a great tribute to this statement with talks on experimental approaches to the origin of life, top notch cell biology and statistical approaches to the behaviour, and output, of cell populations.

The change in the field has been remarkable. Daniel St Johnston commented to me during the meetinh how we can now see that cell biology is Physics. Well, actually, cell biology has always been close to Physics, what has happened in the last few years is that looking at real cells, cells in ensembles or organisms, poses much more interesting questions and problems than when we look at them in isolation. That when we ask questions about their Biology rather than their Physics, we do get interesting answers. An approach to cell (and developmental) biology, which sees tissues and organs as ‘living matter’ is important and harbours the future of the biological sciences. A future in which genetics is not only a tool for the discovery of parts but a tool to perturb systems, to test hypotheses posed in the form of detailed models which, as J Skotheim said, need to be taken seriously i.e. building them to make quantitative predictions and testing these predictions in the terms dictated by the models. And this is another of the issues raised by the Physics of Living Matters: models are the path to mechanisms. But models, not as cartoons of a process but in the sense that an engineer uses them, as ways to test the functioning of a system through a mechanism. There was much of this at PLM10.

PLM10 was the annual gathering of a community that is growing, a community that breaks the disciplinary barriers to solve interesting problems. Surely there are many meetings on this topic but with its 10th anniversary (duly celebrated with a great party which included cells and tissues dancing in the background to the tunes of a great band) but PLM continues to be a unique one because of its grass roots origin, the breadth of its content and its emphasis on the meat of the topic: biological systems, living matter a way of doing Biology which sees tissues and organs as a matter of Genes, Cells and Numbers.

PLM10 was a tribute to all this and it was good to see that the future is being built on a solid basis. Importantly I want to highlight here the interactions constructive interactions between UCL and Cambridge on PLM which continue to build a community and, in particular my colleagues Ewa Paluch, Buzz Baum,. Kristian Franze, Alexander Kabla and specially An Tyrrell for organizing a meeting that seems to go from strength to strength. PLM11, September 2016, is on the horizon; keep it as a date in your diaries!

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