Bacterial ticker tape puts cells on display

When a bacterium multiplies on a surface, its offspring typically stay close. They pile up in mounds, making it difficult to study individual cells. Researchers have now built a transparent array of nanochannels where microbes grow single file so they can study a bacterium and its daughter cells over multiple generations (Anal. Chem. 2016, DOI: 10.1021/acs.analchem.6b00889). Tracking single cells in this way could help identify how microbes acquire traits such as antibiotic resistance. Stephen C. Jacobson and colleagues at Indiana University, Bloomington, fabricated a ladder-shaped pattern in a polymer film on a glass slide and covered it with another glass layer. Microchannels for supplying nutrient medium formed the ladder’s side rails, and nanochannels several hundred nanometers wide—matching the width of the bacteria—formed the rungs. The team first confirmed that Bacillus subtilis bacteria grew at the same rate in the device as in standard culture. Next, they engineered a B. subtilis strain to carry a green fluorescence gene controlled by a genetic element known to be activated in only a fraction of cells in a population. Over five generations, the team tracked which cells glowed and which didn’t. Daughter cells were more likely to glow if their parent did, but the correlation declined with every generation.