Images and the Development of the Microbial Biofilm Concept

Scientific researchers have studied microorganisms since the emergence of the single lens microscope in the 17th century. Since then, researchers designed and published many thousands of images to record and share their observations, including hand-drawn diagrams, photomicrographs, and photographs. Images shaped how researchers conceived of microorganisms, their concepts of microorganisms shaped their images, and their images and concepts were shaped by the contexts in which they were working. Over time, the interplay of images and concepts in various research contexts participated in the development of new concepts related to microorganisms, like the “biofilm” concept, or the idea that bacteria exist in nature as complex aggregates attached to surfaces via extracellular polymeric matrices. Many histories of microbiology locate the origin of the biofilm concept in the 1970s, but that date obscures the rich history of research about attached microbial aggregates that occurred throughout the history of microbiology. I discovered how the interplay of images and concepts related to bacteria participated in the development of the biofilm concept by documenting when and why researchers used different visual features to represent changing concepts related to microorganisms. I specifically examined how and why scientists represented evolving concepts related to bacteria during the 17th century (Chapter 1), from the late 17th century to the early 20th century (Chapter 2), and during the first seventy-four years of the 20th century (Chapter 3). I discovered the biofilm concept developed in at least three unique research contexts during the 20th century, and how images reflected and shaped the concept’s development in each case. The narrative and collection of images generated from this work serve as a visual history of the development of scientists’ ideas about the nature of bacteria over 300 years.