Abstract: Methods for characterizing micro-organisms may include (a) depositing micro-organisms on a porous medium with a first and a second surface and pores extending from the first surface to the second surface; (b) arranging the porous medium on the surface of a nutrient medium contained in a chamber, the second surface being arranged in contact with the nutrient medium; (c) moving the porous medium in relation to the chamber; (d) positioning the porous medium between an infrared light source and an image sensor, the light source being configured to emit an incident light wave in an emission wavelength; (e) illuminating micro-organisms retained on the porous medium, using the light source and acquiring an image using the image sensor, the image allowing an observation of at least one colony of micro-organisms; and (f) characterizing the colony of microorganisms from the image acquired in the illuminating (e).