Research from as early as 2021 has shown that flowering plants produce methanol as they grow and demethylate pectin monomers in their cell walls. With the sheer amount of vegetative biomass on the planet, this amounts to a staggering 100 teragrams per year. However, even in low concentrations, methanol can have harmful effects. Certain microbes known as methylotrophs are able to act as a methanol sink by using it as a carbon source. These microbes are found in plant phyllo- and rhizospheres alike. Despite the presence of methylotrophy in multiple classes of bacteria, not all classes of are represented equally in metagenomic samples. A literature review of the genus Methylophilus reveals that several methanol-utilizing microbes isolated from plants cluster together when their phylogeny is plotted. Further investigation of this clustering reveals a set of genes unique to these plant-based isolates of Methylophilus, with an implication that they produce enzymes that can assist in pectin biosynthesis. Despite Methylophilus being a Betaproteobacteria with many qualities that would enable symbiosis with plants, an overview of metagenomic data from the Anza Borrego Desert shows that Betaproteobacteria are consistently outnumbered by Alphaproteobacteria both in overall proportion and in methylotrophic proportions. A set of microcosm experiments in vivo suggests that this microbial interaction with plants is not mediated by the ability of the microbes to process methanol, but most likely by their other more general metabolic capabilities correlated with taxonomical affiliation.
