Thinking Hard and Deep about the Very Small: A Review of Philosophy of Microbiology

I think it is generally true that all infectious disease physicians love microbiology. However, it is also probably true that most infectious disease physicians think of medical microbiology as their handmaiden — a powerful tool that allows them to make diagnoses, treatment decisions, and predictions. Microbiology as such is something that is often neglected not only by physicians but also by philosophers of science who are often focused on “bigger” entities when they delve into the philosophical questions posed by biology.


Philosopher Maureen A. O’Malley addresses these issues and much much more in an intellectually challenging and rigorous book aptly entitled Philosophy of Microbiology. O’Malley motivates her call for more attention to the philosophy of microbiology by calling to attention the fact that microbes are the “most important, diverse and ancient life forms on our planet. The science of these organisms, microbiology, is the science of the most significant living entities and their influence on all the rest of life.” Additionally if one looks at eukaryotes, it is the single-celled protists that dominate multicellular organisms.

The book provides great amounts of information on just how important microbial life is to all ote life and is full of facts that should be kept in mind such as the diversity of metabolic pathways possessed by bacteria, the role of cyanobacteria in the Great Oxidation Event, the oxygenation power of plants being derived from endosymbiont bacteria, conversion of carbon, nitrogen fixation, and much more.

One of the most fascinating discussions in the book is that on teleosemantics, “the philosophical study of how mental content can be explained naturalistically” and its relationship with magnetotactic bacteria, that “sense” the planet’s geomagnetic field.

There are also fascinating sections that deal with the implications of lateral gene transfer (LGT), phylogeny/classification, the pangenome, and microbial “communities.” Not only does the book prompt the reader to think harder about microbiology, it prompts one to consider well-established facts from a wider context.

It’s hard to do give O’Malley’s book the justice it is due in a brief blog post but it is really a clarion call to take microbiology much more seriously from a philosophical standpoint. As she writes:

“There are no eukaryotes without mitochondria, and (within eukaryotes) no plants without chloroplasts”

“The origins of life are exclusively microbial; life until recently was exclusively microbial; life in the future will most probably be exclusively microbial too. If there is indeed life on other planets in other galaxies, it is most likely to be exclusively microbial”

For those who want to think rigorously, endlessly, and deeply about microbiology, I highly recommend the book.