Rain dance makes rain
This week I’m working on the next edition of Microbiology: An Evolving Science. So we’ll explore some of the more extreme discoveries about our microbial friends. For starters: Microbes might cause a rain dance to actually make rain.
Our best model for precipitation says that bacteria make rain; that is, the physical form of a bacterium is needed to “nucleate” formation of rain droplets or hail. Several studies offer evidence, most notably the work of Brent Christner. Christner showed the ubiquitous presence of “biological ice nucleators” — that is, bacteria, within the core of snowflakes and hail. Particular species are found, especially plant pathogens such as Pseudomonas syringiae.
Study of clouds reveals a surprisingly steady population of bacteria upon suspended dust particles. But how do the dust and bacteria get up there? Here is where the rain dance might come in. Another study showed a surprising correlation of hail storms with tea plantations in Kenya. The authors propose that tea plant litter (presumably full of bacterial plant pathogens) forms highly effective hail nucleators, once it gets kicked up into the air by the tea harvesters. So, could it be possible for a large tribe full of dancers in a dry season to kick up enough dust to trigger a rain shower?
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Ultraphyte 
Wow! So even the ‘water cycle’ is part of the biosphere–that’s a mind-blower.
It’s so strange to be well-educated and fifty-five years old, yet every day I find news of more amazing stuff, proven contradictions of long-held beliefs, and twists to the complexity of the whole thing, such as you have offered here.
It reminds me of the Ents in Tolkien’s books– I am an aging tree, and as I grow older I spend less time running around and more time just thinking over all the information that comes at me–If I’m not careful, I’ll start to grow roots
Pseudomonas syringae, and its ability to convert superchilled water to ice extremely quickly, makes a nice classroom demonstration, as well. I learned about this from some of Jo Handelsman’s postdocs years ago, and made it a staple of my own microbiology course. Here are two YouTube videos I made demo’ing the effect:
When will the new edition of “Microbiology” coming out?
That’s cool. Does only Pseudomonas work? Not plain dust?
Don’t hold your breath for 3E–we’ve just started gathering material. Any comments you have on 2E, now’s the time.
I do know, in the demonstration I set up and have done repeatedly, a bit of ice catalyzes the rapid change. E. coli does not. E. coli containing the “ice nucleation protein” gene does. I think it has to do with the superchilling…at some point, dust is fine. But I have gotten the “reaction” to take place at -4 degrees C. with P. syringae pretty reliably.
So would injecting the bacteria into clouds be a better solution to creating rain than silver iodide?
And do they replicate up there, meaning injections wouldnt have to be so frequent?
I haven’t seen a controlled experiment between silver iodide and bacteria. I think the bacteria may be more effective because they have evolved a specialized protein for ice nucleation.
Do the bacteria replicate in the stratosphere? Until recently, it was thought that no, the bacteria only came up passively on dust particles. But recent studies are investigating whether the bacteria actually grow. The dust lasts a long time, and there is plenty of moisture.
The ice nucleation protein looks pretty small, just 48 aa’s and these are 3 repeats of 16 aa sequences.
ice nucleation protein
Is this sequence optimal, or can it be improved? Can the protein alone be used, rather than as part of the cell surface of a bacterium? Could it be used to create ice in seawater, partially ameliorating ice cover loss at the poles?
Has this ice nucleation protein been mapped across the planet? It would be very interesting if this protein rather than wind/humidity was behind desertification – Sahara, Gobi, Australian outback, etc. If yes, then reseeding this protein could greatly increase total arable land.
Alex:
The ice nucleation protein has gone extensive selection globally, so I don’t know how it might be improved, but that’s an intriguing idea. It only makes ice in supercooled water (water cooled below the freezing point) so I don’t know about seawater.
Mark Martin says he’ll add more later.
I believe the protein works in water at -5C. I don’t know is surface seawater may get that low if it can be cooled by winds/ice below the 4C maximum density point, the old data I can find suggest minimum surface temps ~ -1C, i.e. above the threshold.
I am right in thinking that bacteria have been detected in the exosphere, at the edge of space?
Could GM cyanobacteria multiply in clouds, held aloft by size and updrafts, given sufficient water (present) and micro nutrients?
Yes, bacteria have been found up at the “edge of space,” however defined. Wherever there are dust, there are bacteria. And some surprisingly resistant to gamma rays.
Cyanobacteria could multiply in cloud droplets. Marine cyanos multiply about once a day, so I see no reason why they couldn’t up in the air.
Pensar que estas bacetrias son causantes de lluvia es bien aventurado, tomando en cuenta que las nubes basicamente son gotas de agua y cristales…y hay muchas otros factores atmosféricos que entran en juego. Me pregunto qué tan significativo podría ser el papel de estas bacetrias….cuántas se necesitaría para formar cristales suficientes para formar un aguacero….Si cultiváramos suficientes bacetrias en un medio controlado….podríamos hacer lluvia artificial? Sería una solución para las épocas de sequía? Esto es para "dolor de muelas": Se ha investigado que las depresiones estaciones se relacionan con la melanina y serotonina, cuya producción se rige por el reloj biológico (el cual se ve afectado por los cambios estacionales, principalmente por la falta de luz)