Overproduction of NAD+ and 5'-inosine monophosphate in the presence of 10 microM Mn2+ by a mutant of Corynebacterium ammoniagenes with thermosensitive nucleotide reduction (nrd(ts)) after temperature shift.
Corynebacterium ammoniagenes strain CH31 is thermosensitive due to a mutation in nucleotide reduction ( nrd(ts)). The strain was examined for nucleotide overproduction upon shifting the culture temperature to a range of elevated temperatures. No overproduction of NAD(+) was detected in the control maintained at 27 degrees C whereas NAD(+) was accumulated extracellularily by strain CH31 at 37 degrees C and at 40 degrees C. As a result of the temperature shift, division-inhibited cells displayed only limited elongation. This is a characteristic morphological feature of cell-cycle-arrested coryneform bacteria. Ribonucleotide reductase (RNR) activity was inactivated immediately after the temperature shift in the NAD(+)-proficient cultures, leading presumably to an exhaustion of deoxyribonucleotide pools and impairment of DNA replication. In contrast to the low extracellular accumulation of NAD(+), at the non-permissive temperature of 35 degrees C a distinct capacity for intracellular nucleotide overproduction was revealed by a new method using nucleotide-permeable cells. The approach of shifting the culture temperature was applied successfully to the overproduction of taste-enhancing nucleotides in the presence of 10 microM Mn(2+). Concomitant with a dramatic loss of viability, the thermosensitive mutant CH31 accumulated 5.3 g 5'-inosine monophosphate per liter following the addition of hypoxanthine as precursor for the salvage pathway.
Abbouni
Bouziane
B
Institut für Mikrobiologie, Universität Hannover, Schneiderberg 50, 30167 Hannover, Germany.
Elhariry
Hesham M
HM
Auling
Georg
G
D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D002455:Cell Division / Q000235:genetics; D003352:Corynebacterium / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism* / Q000648:ultrastructure; D020043:Genes, Essential; D019271:Hypoxanthine / Q000378:metabolism; D007291:Inosine Monophosphate / Q000096:biosynthesis*; D008345:Manganese / Q000378:metabolism*; D009154:Mutation; D009243:NAD / Q000096:biosynthesis*; D010539:Permeability; D012264:Ribonucleotide Reductases / Q000235:genetics / Q000378:metabolism; D013696:Temperature
D001426:Bacterial Proteins; D009243:NAD; D007291:Inosine Monophosphate; D019271:Hypoxanthine; D008345:Manganese; D012264:Ribonucleotide Reductases