Although Betsey Dexter Dyer does tell us how to find bacteria using a microscope, she points out that usually we would be seeing ‘nearly featureless dots and dashes’ (p. 4). Instead, she focuses her Field Guide book on ‘field marks,’ features visible or detectable (smells, sounds, etc) at our macroscopic level, and she tells us in what sorts of habitats we are most likely to find these field marks and their associated bacteria.
Again and again, in the course of explaining different groups of bacteria, she encapsulates key concepts in microbiology.
“We can consider ourselves and all animals (as well as most protists and all fungi and plants) as living field marks of those long-ago alpha proteobacterial symbionts, as those symbionts are now our mitochondria. Our enormous size, extraordinary level of activity (in spite of gravity), and quick muscles and nervous systems are all testament to the efficiency of mitochondria in gathering energy. And just hold your breath for awhile to remind yourself how obligately dependent we are on oxygen — which, although it continues to be a poisonous gas, has been put to excellent use by our symbiotic bacteria.” (Pp 86-7.)