We propose a novel technique to probe shape of a single microbe embedded in a nematic liquid crystal (NLC) sample by observing geometry of dark brushes with optical microscope using a cross-polarizer set up. Assuming certain anchoring conditions for the NLC director at the surface of the microbe, we determine the resulting shapes of brushes using numerical simulations. Our results suggest that for asymmetrical microbes (such as cylindrical shaped bacteria/viruses), resulting brushes may carry the imprints of this asymmetry (e.g. the aspect ratio of cylindrical shape) at relatively large distances to be able to be seen using simple optical microscopy even for microbe sizes in few tens to few hundred nanometer range. •We show that brush geometry in a crossed polarizer setup can probe shapes of microbes in a nematic liquid crystal sample.•We determine the resulting shapes of brushes using numerical simulations.•We find that for cylindrical microbes, brushes carry the imprints of aspect ratio of cylindrical shape.•This can be detected using optical microscopy, even for microbe sizes of few tens to few hundred nanometers.•For spherical microbes, e.g. corona virus, symmetric brushes can help distinguishing from asymmetric impurities/microbes.