Marine microbiology is the study of the smallest organisms found in the oceans—bacteria and archaea, many eukaryotes (among the protozoa, fungi, and plants), and viruses. Most microorganisms can be seen only with a microscope. Microbes pervade the oceans, its sediments, and some hydrothermal fluids and exhibit solitary life styles as well as complex relationships with animals, other microorganisms, and each other. The skeletal remains of microorganisms form the largest component of sedimentary fossils whose study reveals Earth’s history. The enormous morphological, physiological, and taxonomic diversity of marine microorganisms remains far from adequately described and studied. Because the sea receives terrestrial microorganisms from rivers, sewage outfalls, and other sources, marine microbiology also includes the study of alien microorganisms.
My goals here are to outline how marine microbiology at Scripps Institution of Oceanography has grown throughout the past 100 years; to review the contributions of some of its scientists to the solution of microbiological problems during the twentieth century; and to consider, albeit briefly, in which directions marine microbiology will expand next.