Fig 2. –Melanization patterns of larvae infected with wild-type and AS-fmd P. lutzii strains.

Tissue slides displaying nodules from three different specimens of G. mellonella infected with wild-type (A-C) and AS-fmd strains (D-F) then stained with HE. The images of the blue channel split highlight the melanin spots (G-L). A-C) The three different nodules enclosing P. lutzii wild-type cells show well-defined structures, tight cellular organization, and high intensity of dark regions derived from melanin stain (MS), demonstrating increased levels of melanin. D-F) The mutant cells of P. lutzii are encompassed by three distinct nodules that have softly defined structures, loose cellular disposition, and clear-brown regions, indicating low levels of melanin. G-L) The wild-type and AS-fmd images after digital splitting of the blue channel to evidence melanin. The darker regions of each image indicate high melanized sites, while the clear-brown regions bordering the cell wall indicate low melanized sites (MS). AS-fmd images show yeast cells with a slightly darker color delineating the cell wall (arrowheads).