Dependence of Aspergillus niger on secretions of neighbouring colonies.

Abstract

Heterogeneity can be observed at many different levels in the ascomycete Aspergillus niger. This study mainly focusses on the heterogeneity in the secretion of glucoamylase. To this end, a CRISPR-Cas9 approach was used to create knockout strains for the genes glaA or amyR in a strain that constitutively expresses GFP. Inactivation of either glaA or amyR resulted in abolished growth on starch. Growth was restored when co-culturing either strain with a wildtype. This was studied in more detail by varying the ratio between wild-type and knockout spores in the inoculum. Results showed that the mutant exhibited a growth deficiency when its spores were more abundant in the inoculum. Inoculating a relatively low amount of mutant spores when compared to the wildtype fully restored growth. These data show that A. niger is able to profit from the secretions of neighbouring colonies. Besides this, the growth differences when testing the different ratios indicate that there is an optimal ratio between productive and non-productive hyphae in the co-culture, and perhaps also within one single colony.