Imaging Myxococcus-E. coli Predation Dynamics

Prey invasion was imaged by microscopy using the Bacto-Hubble system the specific details of the Method are described elsewhere (Panigrahi, 2020 (link)). Briefly, cell suspensions concentrated to OD₆₀₀=5 were spotted at 1 mm distance onto CF 1.5% agar pads and a Gene Frame (Thermo Fisher Scientific) was used to sandwich the pad between the slide and the coverslip and limit evaporation of the sample. Slides were incubated at 32°C for 6 hr before imaging, allowing Myxococcus and E. coli to form microcolonies. Time-lapse of the predation process was taken at ×40 or ×100 magnification. Movies were taken at the invasion front where Myxococcus cells enter the E. coli colony. To facilitate tracking, M. xanthus cells were labeled with fluorescence (Ducret et al., 2013 (link)). Fluorescence images were acquired by microscopy every 30 s for up to 10 hr, at room temperature (see below for experimental details of time lapse acquisitions ).