The praise in my review of Nicholas P. Money's new book The Amoeba in the Room: Lives of the Microbes has lots to say about the author's writing (it's really good) but fails to mention that the author is also a fearless thinker. Money is not scared to mention/explain ideas or theories that other scientists would never give the time of day. Money is a grounded and yet not a closed thinker. An explanation for this might be that those who deal with the microscopic world are not in a position to enjoy the certainties and continuities of those who deal with animals or plants. Microbes are weird and constantly challenge our understanding of them and the world we live in. Here Money mentions a very strange idea about the source and possible function of clouds:

A few scientists have arrived at a radically different conclusion, positing that microbes form clouds, use them for dispersal over long distances, and may even cause changes in wind speed that get them airborne in the first place. Much of this highly speculative work falls within the pottiest parts of the Gaia Hypothesis.

The argument about microbes controlling weather patterns for their own devices begins with the idea that clouds are products of a biogenic process involving the formation of water droplets and ice crystals around airborne microbes. The bacterium Pseudomonas syringae is one of these biological rain makers. Pseudomonas infects cereals, peas, beets, and other crop plants. Proteins on its cell surface increase the temperature at which water freezes, inducing ice crystal formation on the leaves of its hosts. The crystals damage the leaves, bathing the bacterium in plant nutrients.

Pseudomonas is found in the atmosphere, along with other bacteria, and its isolation from hailstones supports the idea that it may be a player in cloud formation. Many other microbes have similar ice-nucleating properties and are found in raindrops and snow fakes.

Another biogenic mechanism of cloud formation involves chemical emissions from microbes rather than the physical properties of the cells themselves. Vast blooms of the marine coccolithophorid Emiliania huxleyi operate as huge dimethylsulfde (DMS) factories. DMS synthesis is a by-product of the alga’s method of maintaining hydration (osmotic regulation), and the compound acts as a potent cloud former over the ocean.

The influence of microbes on weather patterns is a powerful illustration of the importance of the microscopic world in controlling the health of the biosphere, but this does not mean that there is any adaptive significance to these physical processes.


What matters for me is not only that Money mentioned this theory but explained the reasoning behind it. No matter how crazy the microbe-cloud connection might sound to you or me, we do see from Money's breakdown that it wasn't pulled out of thin air.
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