The role of initial spore adhesion in pellet and biofilm formation in Aspergillus niger

• Published in: Fungal genetics and biology 2012-01, Vol.49 (1), p.30-38
• Main Authors: Priegnitz, Bert-Ewald, Wargenau, Andreas, Brandt, Ulrike, Rohde, Manfred, Dietrich, Sylvia, Kwade, Arno, Krull, Rainer, Fleißner, André
• Format: Article
• Language: English
• Subjects: Adhesion; alb1; Aspergillus niger; Aspergillus niger - cytology; Aspergillus niger - growth & development; Aspergillus niger - physiology; Biofilm; Biofilms - growth & development; biosynthesis; Biosynthetic Pathways - genetics; Cell Adhesion; conidia; fungi; Gene Deletion; genes; germ tube; Hyphae - physiology; Melanin; Melanins - biosynthesis; mutants; Pellet; pellets; Spores, Fungal - physiology; Surface Properties
• ISSN: 1087-1845; 1096-0937
• DOI: 10.1016/j.fgb.2011.12.002

► We analyzed the contribution of spore adhesion to pellet and biofilm formation in Aspergillus niger. ► Conidial surface was altered by creating a melanin deficient mutant. ► Albino spores have altered surface properties resulting in altered aggregation and adhesion. ► Pellet formation is not influenced by altered spore aggregation. ► Biofilm formation is stabilized in the mutant. Fungi grow on a great variety of organic and inorganic materials. Colony establishment and growth on solid surfaces require adhesion of spores and hyphae to the substrate, while cell-to-cell interactions among spores and/or hyphae are a prerequisite for the development of three-dimensional mycelial structures such as pellets or biofilms. Surface adherence has been described as a two-step process, comprised of the initial attachment of ungerminated conidia followed by further adhesion of the forming germ tubes and growing hyphae. In the present study, we analyzed the contribution of adhesion of ungerminated spores to pellet and biofilm formation in Aspergillus niger. Mutants deficient in melanin biosynthesis were constructed by the deletion of the alb1 gene, encoding a polyketide synthase essential for pigment biosynthesis. Δalb1 conidia have an altered surface structure and changed physicochemical surface properties. Spore aggregation in liquid culture as well as spore surface attachment differ between the wild type and the mutant in a pH-dependent manner. In liquid culture further pellet formation is unaffected by altered spore-spore interactions, indicating that germ tube and hyphal adherence can compensate for deficiencies in the initial step of spore attachment. In contrast, under conditions promoting adhesion of Δalb1 conidia to polymer surfaces the mutant forms more stable biofilms than the wild type, suggesting that initial spore adhesion supports sessile growth.