Atomic Force Microscopy Analysis of gltA Promoter

A 703 base pair (bp) region from the gltA promoter was gel-purified using the QIAquick Gel Extraction Kit (Qiagen) by using primer pairs gltA F and gltA R for S. Typhimurium (-689 bp to + 14 bp) and for E. coli (-694 bp to + 9 bp), respectively. A glutaraldehyde-modified mica surface was prepared as described in Chakraborty et al. (2017) (link). Ten nanograms of the gltA regulatory region was incubated with 30 nM OmpR for 15 min at RT. This mixture was then deposited on the mica for 15 min. Images were acquired on a Bruker Dimension FastScan AFM system using the tapping mode with a silicon nitride cantilever (FastScan C, Bruker). Raw AFM images were processed using Gwyddion software¹.