Fig 1.
Customized lensless prototype.
(a) Drawing and (b) picture of the lensless configuration used to measure phage plaque growth. The prototype is small enough to fit in a standard laboratory incubator (here a Heraterm 18L).
Fig 2.
Algorithm structure to count phage plaques.
Fig 3.
Image processing for plaque growth kinetics study.
(a) Unprocessed phage plaque image (b) After a Gaussian blur filtering (c) Binarized final image.
Fig 4.
Acquisition of single-layer agar assay through lensless imaging.
(a) Image of a single-layer soft agar assay after 21 hr 44 minutes of incubation at 37°C, with the dark background corresponding to the area of bacterial growth and bright disks to lysis plaques. The orange arrows indicate plaques that were not excluded from the growth kinetics study. (b) Corresponding plaque radius histograms and (c) cumulative graph of plaques detected as a function of time.
Fig 5.
Evolution of the mean gray level (red curve) of bacterial lawn and its variation (black curve).
The gray level variation is the derivative of the mean gray level. It highlights the evolution of the growth rate of the bacteria inside the lawn. It is maximal after 2 hr of incubation.
Fig 6.
Growth of plaque radius over time.
(a) Plaque expansion on plates expressed as μm radius as a function of time for the nineteen plaques considered. Larger plaques were those that started to grow earlier than smaller plaques. (b) Representative examples of linear fits of the curves obtained in the first 10 hr of incubation for plaques of various final radii. The slopes of the fitted curves correspond to the growth rate of the respective plaques.
Fig 7.
Study of plaque growth rates over time.
Plaque growth rates vs time. (a) At 15 hr of incubation, the mean growth rate stabilized for all plaques independent of the size reached by the end of the experiment. (b) The mean growth rates during phase III were determined for each group.
Fig 8.
Lensless imaging of K. pneumoniae bacterial microcolonies developing within plaques after 23 hr of incubation.
The red arrows indicate microcolonies within plaques.