To further explore the role of melanin in the extremely
halotolerant character of H. werneckii, we studied the effects of several melanin
biosynthesis inhibitors on its growth, pigmentation and cell morphology. The most potent
inhibitors were a 2,3-dihydrobenzofuran derivative and tricyclazole, which restricted the
growth of H. werneckii on high-salinity media, as shown by growth curves and plate-drop
assays. These inhibitors promoted release of the pigments from the H. werneckii cell surface
and changed the medium colour. Inhibitor-treated H. werneckii cells exposed to high salinity
showed both decreased and increased cell lengths. We speculate that this absence of
melanin perturbs the integrity of the cell wall in H. werneckii, which affects its cell division
and exposes it to the harmful effects of high NaCl concentrations. Surprisingly, melanin
had no effect on H. werneckii survival under H2O2 oxidative stress.