Growth curves of filamentous fungi
Background: Browsing through microbiology textbook reveals that growth of microorganisms in batch cultures shows distinct growth phases (i.e. lag, exponential, stationary and declining phase). The assumption implied by the textbook growth curve is, that growth is terminated immediately after depletion of the first essential nutrient – irrespective of the nature of this essential nutrient. However, this schema often fails to describe the complex growth dynamics of many filamentous fungi in batch culture. Neglecting these deviating growth dynamics can lead to erroneous experimental standardisation and results, since physiological properties are strongly dependent on the nutritional status and thus on the growth phase.
Topics: Our research focuses on how different nutrient depletions affect growth dynamics of our model organism Penicillium ochrochloron (formerly identified as Penicillium simplicissimum). We are especially interested in the various physiological adaptation mechanisms of this organism to cope with rapidly varying environmental conditions and why this leads to growth progresses, which strongly differ from the textbook growth curve.
Methods: Growth dynamics of Penicillium ochrochloron are investigated in highly standardised bioreactor batch cultures with online recording of oxygen consumption, carbon dioxide formation and other cultivation parameters. Cultivations are performed with well-defined minimal media as well as controlled pH, temperature and aeration. Nutritional status, nutrient uptake, excretion of organic acids, intracellular metabolite concentration and biomass formation are determined with a high sampling frequency.
Regulation of overflow metabolism in filamentous fungi: dynamics of plasma membrane, energy metabolism and respiratory chain – in dependence of nutrient limitations, exhaustions and growth phases illustrated by Penicillium ochrochloron (Austrian Science Fund Project P22220, 2010-2013)
Vrabl P., Schinagl C. and Burgstaller W. 2009. Growth kinetics of filamentous fungi in batch culture: textbook knowledge and reality. Mycoses 52: 430.
Vrabl P., Mutschlechner W. and Burgstaller W. 2009. Dynamics of adenine nucleotides and energy charge during uncoupling of catabolism and anabolism in Penicillium ochrochloron. Mycological Research 113: 1422-1432.
Vrabl P., Mutschlechner W. and Burgstaller W. 2008. Characteristics of glucose uptake by glucose- and NH4-limited grown Penicillium ochrochloron at low, medium and high glucose concentration. Fungal Genetics and Biology 45: 1380-1392.