Katherine writes:

Dear TWIM 

Thank you for a wonderful podcast…

Recently discussed was the possible role of using microbes to degrade plastic waste. Many months ago, you discussed electrifying microbial fuel cells. Could microbes degrade plastic and then transfer the energy to microbial fuel cells?



Brian writes:

Dear TWIM,

Thanks so much for your generosity in sharing science.

About the apple microbiome… 

2 decades ago I started a coop in Cote d’Ivoire, West Africa, making palm wine brandy. It ended in civil war. But I learned much more than I need to know about distilled spirits. The most interesting is Calvados, the french distillate of apples.

In the US we make cider, and now some make apple brandy, from single varieties of apples. Gravenstein, for example. Calvados, which comes from Normandy district in France, is made from about 100 different varietals, grown on the same properties. 

Only 10% or 20% are sweet apples. Most are bitter or sour, which are very different. Calvados, like all unadulterated distillates, has no residual sugar. All you get is the “essence” of apples, so its makers aim to provide a breadth of possible flavors.

There’s remarkably little research, that I could find, on the Calvados apple orchard microecosystem. Possibly it evolved by planting seeds, since apple trees do not grow “true”, but express different ancestral traits. I doubt that you can purchase hundreds of different sour and bitter apple stock. 

On microbiomes, the Abdelfattah et al. survey found country effect explained more fungal and bacterial variance than orchard-level, for a single apple varietal, Gala. There was a sub-continental effect, with European, new world, and eastern Mediterranean areas showing different microbiome clusters. Something similar has been shown in both maize and citrus rhizopheres, where geographical location had a greater microbiome impact than genotype variation.

But these studies examine monocrops. A logical experiment would be to examine situations with many varieties together. Someone should examine Calvados apple orchards. There’s no other agricultural situation I know of where hundreds of different varieties of a single lineage grow together.

Do microbiomes of Calvados orchards have a similar variation level as single variety orchards? If not, does whatever difference they exhibit inform of the impact of monocrops on microbiomes? 

It’s possible that abandoned old apple orchards in northeastern North America have second or third generation trees, which express many different varieties “by accident.” These could be analyzed to examine the relative weight of geographic difference.

Ah, I’m no longer in academia, and was never a fruit guy. But wish I could do something like this. Also, those old orchards might make some pretty good cider. There’s a little still in my garage waiting to find a new world Calvados.

Keep up the good work!