We provide a brief review of the development and application of the Mesolens and its impact on microbiology. Microbial specimens such as infected tissue samples, colonies surfaces, and biofilms are routinely collected at the mesoscale. This means that they are relatively large multimillimetre-sized samples which contain microscopic detail that must be observed to answer important questions across various sectors. The Mesolens presents the ideal imaging method to study these specimens as no other optical microscope can thanks to its unique combination of low magnification and high numerical aperture providing large field-of-view, high-resolution imaging. We demonstrate the current applications of the Mesolens to microbial imaging and go on to outline the huge potential of the Mesolens to impact other key areas of microbiology.
K E Y W O R D Sbiofilm, high-content imaging, mesoscopic imaging, microbiology From Louis Pasteur's disproof of spontaneous generation to Robert Koch's germ theory, our understanding of microorganisms has crucially depended on optical microscopy. Microscopes, essentially like those used by Pasteur and Koch, are still indispensable today as a complement to biochemical and molecular methods in the diagnosis of infection.However, despite its widespread application in microbiology, the optical microscope has not changed in basic design for over 100 years. The ratio of magnification to numerical aperture (NA) has been set to a fixed value of approximately 40:1 for all microscope objectives. The reason for this is wholly historical: this proportion gives an image in which the detail is suited to the capacity of the human eye. 1 In microbiology, a 4× NA 0.