Simultaneous utilization of glucose and sucrose by thermophilic fungi.
The utilization of mixtures of glucose and sucrose at nonlimiting concentrations was studied in batch cultures of two common thermophilic fungi, Thermomyces lanuginosus and Penicilium duponti. The sucrose-utilizing enzymes (sucrose permease and invertase) in both fungi were inducible. Both sugars were used concurrently, regardless of their relative proportion in the mixture. At the optimal growth temperature (50 degrees C), T. lanuginosus utilized sucrose earlier than it did glucose, but at a suboptimal growth temperature (30 degrees C) the two sugars were utilized at nearly comparable rates. The coutilization of the two sugars was most likely possible because (i) invertase was insensitive to catabolite repression by glucose, (ii) the activity and affinity of the glucose transport system were lowered when sucrose was included in the growth medium, and (iii) the activity of the glucose uptake system was also subject to repression by high concentrations of glucose itself. The concurrent utilization of the available carbon sources by thermophilic fungi might be an adaptive strategy for opportunistic growth in nature under conditions of low nutrient availability and thermal fluctuations in the environment.
Maheshwari
R
R
Department of Biochemistry, Indian Institute of Science, Bangalore.
Balasubramanyam
P V
PV
D001692:Biological Transport; D003470:Culture Media; D004790:Enzyme Induction; D029968:Escherichia coli Proteins; D005656:Fungal Proteins / Q000096:biosynthesis; D005947:Glucose / Q000378:metabolism*; D006026:Glycoside Hydrolases / Q000096:biosynthesis; D007700:Kinetics; D026901:Membrane Transport Proteins / Q000096:biosynthesis; D003904:Mitosporic Fungi / Q000201:enzymology / Q000254:growth & development / Q000378:metabolism*; D010407:Penicillium / Q000201:enzymology / Q000254:growth & development / Q000378:metabolism*; D013395:Sucrose / Q000378:metabolism*; D013696:Temperature; D043324:beta-Fructofuranosidase
D003470:Culture Media; D029968:Escherichia coli Proteins; D005656:Fungal Proteins; D026901:Membrane Transport Proteins; C056379:cscB protein, E coli; D013395:Sucrose; D006026:Glycoside Hydrolases; D043324:beta-Fructofuranosidase; D005947:Glucose