Heterogeneity in micro-colonies of Aspergillus niger in liquid shaken cultures

Charissa de Bekker, G. Jerre van Veluw, Arman Vinck, L. Ad Wiebenga, Han A.B. Wösten

Author address: 

Microbiology and Kluyver Centre for Genomics of Industrial Fermentations, Institute of Biomembranes, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands

Abstract: 

Colonies of the filamentous fungus Aspergillus niger secrete large amounts of proteins. Previously, it has been shown that on solid media only part of the colony participates in secretion. We assessed whether heterogeneity can also be found between and within micro-colonies of A. niger from submerged cultures. Strains expressing GFP from the glucoamylase (glaA) or ferulic acid esterase (faeA) promoters were grown. The Complex Object Parametric Analyzer and Sorter (COPAS) was used to analyze the diameter and fluorescence of micro-colonies. At least two populations were found in these cultures, one population of small (25%) and one of large micro-colonies (75%). Fluorescence correlated with volume. 27% and 73% of the micro-colonies expressing GFP from the faeA promoter were lowly and highly fluorescent, respectively. This implies that heterogeneity in this strain depends on the volume only. In contrast, lowly fluorescent micro-colonies of the glaA::GFP strain comprised about 79% of the culture; this implies an additional factor besides volume. To assess heterogeneity within a micro-colony, central and peripheral parts were isolated by laser microdissection and pressure catapulting (LMPC). QPCR showed that glaA and faeA expression is similar in both zones. However, RNA content per hypha was 50 times higher in the periphery. Here, COPAS and LMPC were used for the first time to assess gene expression in a microbial system. Our results show heterogeneity between micro-colonies from a submerged culture. Moreover, it is shown that zones within a pellet are also heterogenic. Peripheral hyphae have about 50 times more RNA than central hyphae
2010

abstract No: 

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Full conference title: 

10th EUROPEAN CONFERENCE ON FUNGAL GENETICS
    • ECFG 10th (2010)