This is the title my friend Fred Neidhardt recently used for a talk, and a good question it is. I suppose that most microbiologists and the readers of this blog would split the answer down the middle, the biomass of this planet and the chemical transactions therein being about half microbial, half everything else. However, it’s safe to say that most people, many scientists included, are unaware of the colossal importance of the microbial half, not only in biology and medicine but in geology, meteorology, and in our Earth’s habitability. This state of affairs should not be unexpected, given that we have only became aware of much of this during the last few decades. I lived roughly the first half of my life carrying only a vague notion of the global importance of the microbial world. But now we know, and the word needs to go out. A measure of microbial literacy is required for anyone to understand the workings of our living planet.
(Top) Upper atmospheric oxygen concentration, as a percent of current levels, plotted against geological time. (bottom) Phylogenetic history of life on Earth, scaled to match the oxygen timeline. Note that the origin of the eukaryotes and the subsequent diversification of animals both correspond to periods of increasing atmospheric oxygen. Source.
Through the years, many influential writers have endeavored to convey the global influence of microbes to scientists and non-scientists alike. We can now add to these efforts a new contribution that speaks to scientists of all spheres, but especially to other biologists. It was recently published as a Perspective in PNAS, a most appropriate venue. Entitled Animals in a bacterial world, a new imperative for the life sciences, it is authored by 26 scientists whose names are bracketed by those of Margaret McFall-Ngai and Jennifer Wernergreen. It deals specifically with the role of microbes in the lives of animals. While interactions with plants and the inanimate environment are not included, this seems a fitting focus given the anthropocentric interest of most readers. The other stories are for another day, to include the viruses, the most numerous of all players and which interact with all other living things.