Patterns: the same living thing, from molecule to society

A pattern is a problem a cell keeps running into, plus the way living matter solves it. A swimming cell has to turn information about its surroundings into a decision, and that happens in a receptor cluster, in a signalling chain, in a whole chemotaxis module. Each of those is a pattern. Each pattern page gives the problem, the mechanism, a figure drawn at true size, and links to its parts and to the larger wholes it sits inside.

Borrowed from an architect

We took the idea from an architect, and we're not sorry. Christopher Alexander wrote A Pattern Language (1977) to describe how a town or a house is built from solutions that recur. A pattern in his sense names a problem in context and gives a solution that works wherever that problem shows up. We borrowed the form because cells look like they work the same way. A feedback loop that resets a sensor appears in a bacterium and in a retina, and it's useful to describe it once and then say where else it turns up. Whether it's the same solution or a similar one that evolved twice is often an open question, and each page says so.

Six rungs, and every rung a part of the next

Every pattern sits on one of six rungs: molecule, complex, module, organelle, cell and collective. A pattern is built from smaller ones and is itself a part of larger ones. The flagellar motor, for example, is part of the chemotaxis module and also part of the swimming cell. Patterns talk to each other through what crosses their boundary, such as a signal, energy or matter, so a part can be redrawn or swapped for a rival explanation without rewriting the page above it.

Why start with one small bacterium

We began with chemotaxis in E. coli because it's among the best-mapped decision systems in any cell, and because there's single-cell data to check a figure against. Start where the lights are on. The first five patterns follow one thread from the outside in: the adaptation loop, the receptor cluster, the signalling pathway, the flagellar motor and the chemotaxis module that contains them. Every idea and pattern is a draft that's open for review. The Manifesto is the only piece that's been published in a final version.

We don't yet know how far the patterns carry. Some may hold for yeast, slime molds and ciliates, and some may turn out to belong to bacteria alone. The pattern pages for those cells will tell us.