Extending fluorescence microscopy into anaerobic environments

Fluorescence microscopy is a powerful tool for investigating living cells. While widely used fluorescent proteins, such as green fluorescent protein (GFP), have had huge impact in biological imaging because they provide genetically encoded, highly specific labeling, these probes require oxygen to generate fluorescence. This crucial oxidative step has limited the use of GFP-like proteins in anaerobic bacterial systems and restricted live-cell studies of obligate anaerobes and their biology. This review discusses alternative approaches to labeling proteins in anaerobic bacteria that are compatible with live-cell fluorescence microscopy in strict oxygen-free environments. The advantages, disadvantages, and likelihood of successful implementation for each approach are considered to provide context and guide further advances in anaerobic fluorescence labeling.