Summary auto-generated
This 1969 study examined growth kinetics of three fungi—Aspergillus nidulans, Mucor hiemalis, and Penicillium chrysogenum—on solid and submerged media. On solid medium, A. nidulans colonies displayed four growth phases: lag, exponential, deceleration, and constant rate. In submerged culture, growth patterns resembled those of unicellular organisms, exhibiting lag, exponential, and stationary phases. The researcher investigated how glucose concentration, medium depth, oxygen pressure, and temperature affected colony radial growth rate, hyphal density, and hyphal diameter. Key findings included a linear relationship between colony radial growth rate and log of initial glucose concentration at low glucose levels, with maximum growth occurring at much lower glucose concentrations (0.075–0.2 g/L) than for bacteria. Interestingly, germ tube specific growth rates were 2–2.7 times greater than submerged culture growth rates. Colony radial growth rates could not reliably indicate relative specific growth rates among different fungal species, as M. hiemalis showed rapid colony growth despite slower submerged growth rates. Oxygen did not limit growth even at high glucose concentrations. The filamentous growth habit allowed fungi to regulate hyphal density efficiently, enabling rapid spread across nutrient-poor substrates.
Key findings
- A. nidulans colonies exhibited four distinct growth phases on solid medium: lag, exponential, deceleration, and constant-rate linear growth.
- Colony radial growth rate increased linearly with the logarithm of initial glucose concentration, reaching maximum growth at much lower glucose levels (0.075–0.2 g/L) than bacterial colonies require.
- Germ tube specific growth rates were 2–2.7 times faster than specific growth rates in submerged culture, indicating differential growth dynamics between developmental stages.
- Colony radial growth rates cannot be used as a reliable measure of relative specific growth rates among different fungal species.
- Filamentous fungi efficiently regulate hyphal density at the colony periphery based on nutrient availability, allowing rapid growth on low-nutrient substrates while growing more densely on nutrient-rich media.
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Abstract
SUMMARY: The growth kinetics of Aspergillus nidulans, Mucor hiemalis and Penicillium chrysogenum on solid media and in submerged culture were studied. Growth of A. nidulans colonies on solid medium can be divided into the four phases of lag, exponential, deceleration and constant growth rate. The growth kinetics of A. nidulans in submerged culture were similar to those commonly found for unicellular micro-organisms. The effects on colony radial growth rate, of glucose concentration, medium depth, oxygen partial pressure and temperature were studied. The radial growth rate of glucose-limited colonies of A. nidulans increased linearly with the log. of the initial glucose concentration. The effects of glucose concentration on internode length, hyphal density and hyphal diameter were also studied. At glucose concentrations above 1 % (w/v) there was an inverse relation between the radial growth rate of A. nidulans colonies and their peripheral hyphal density. The relations between colony radial growth rate (Kr) and germ tube specific growth rate (αg) on solid media and specific growth rate in submerged culture (αs) were investigated. Direct proportionality between Kr and αs of A. nidulans was found by varying specific growth rate by temperature changes. The germ tubes of A. nidulans conidia grew exponentially at a rate which was about 2·3 times as great as the specific growth rate of the organism in submerged culture. The colony radial growth rates of the three moulds could not be used as a measure of their relative specific growth rates in submerged culture.