Abstract The diesel fungus Amorphotheca resinae can influence corrosion in fuel infrastructure. We compared six isolates in their interaction with carbon steel using two carbon sources, glucose and a 7% biodiesel (B7) blend. All isolates accelerated uniform corrosion with glucose, while with biodiesel, A. resinae had no effect on uniform corrosion but inhibited localised corrosion. The secretion of a melanin-like polymer occurred only in the presence of glucose and carbon steel. Using CRISPR/Cas9-mediated genome editing, we generated and tested melanin-deficient (Δ pks1 , Δ cmr1 ) and constitutive melanin-producing strains of A. resinae . The localised corrosion rates were reduced for melanin-deficient mutants, while the uniform corrosion rates remained unchanged. Addition of secreted melanin to abiotic set-ups increased the uniform corrosion rate. These findings suggest that melanin (cell wall-bound and/or secreted) promotes localised corrosion, whereas secreted melanin accelerates uniform corrosion. The fungus-steel interaction depends both on the cellular physiology and the carbon source, highlighting the complicated role of fungi in carbon steel corrosion.
Gerrits et al. (Tue,) studied this question.