γ-Heptalactone is an endogenously produced quorum-sensing molecule regulating growth and secondary metabolite production by Aspergillus nidulans

• Published in: Applied microbiology and biotechnology Vol. 96; no. 3; pp. 773 - 781
• Main Authors: Williams, Headley E., Steele, Jonathan C. P., Clements, Mark O., Keshavarz, Tajalli
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer-Verlag 01-11-2012; Springer
• Subjects: Applied Microbial and Cell Physiology; Aspergillus nidulans; Aspergillus nidulans - growth & development; Aspergillus nidulans - metabolism; Aspergillus nidulans - physiology; Biomedical and Life Sciences; Biotechnology; Chromatography, Liquid; Esters; Gene expression; Gene Expression Regulation, Fungal; Lactones - isolation & purification; Lactones - metabolism; Life Sciences; Liquid chromatography; Magnetic Resonance Spectroscopy; Mass Spectrometry; Metabolites; Microbial Genetics and Genomics; Microbiology; Nuclear magnetic resonance spectroscopy; Quorum Sensing; γ-Heptalactone; Quorum-sensing molecule; Growth phase regulation; Penicillin
• ISSN: 0175-7598; 1432-0614
• DOI: 10.1007/s00253-012-4065-5

Microbes monitor their population density through a mechanism termed quorum sensing. It is believed that quorum-sensing molecules diffuse from the microbial cells and circulate in the surrounding environment as a function of cell density. When these molecules reach a threshold concentration, the gene expression of the entire population is altered in a coordinated manner. This work provides evidence that
Aspergillus nidulans
produces at least one small diffusible molecule during its growth cycle which accumulates at high cell density and alters the organism's behaviour. When added to low-density cell cultures, ethyl acetate extracts from stationary phase culture supernatants of
A. nidulans
resulted in the abolition of the lag phase, induced an earlier deceleration phase with 16.3 % decrease in the final cell dry weight and resulted in a 37.8 % increase in the expression of
ipnA::lacZ
reporter gene construct, which was used as a marker for penicillin production compared to non-treated controls. The bioactive molecule present in the stationary phase extract was purified to homogeneity and was identified by liquid chromatography-mass spectrometry and nuclear magnetic resonance spectroscopy to be γ-heptalactone. This study provides the first evidence that
A. nidulans
produces γ-heptalactone at a high cell density and it can alter the organism's behaviour at a low cell density. γ-Heptalactone hence acts as a quorum-sensing molecule in the producing strain.