Method for isolating mutants overproducing nicotinamide adenine dinucleotide and its precursors

Area of Science:

• Microbiology
• Molecular Biology
• Biochemistry

Background:

• Nicotinamide adenine dinucleotide (NAD) is crucial for cellular metabolism.
• Understanding NAD metabolism is key to cellular function and disease research.
• Previous methods for isolating NAD metabolism mutants were limited.

Purpose of the Study:

• To develop and apply a novel procedure for isolating mutants defective in NAD metabolism.
• To characterize the pyridine metabolism of isolated Escherichia coli mutants.
• To classify these mutants based on their NAD metabolism profiles.

Main Methods:

• Utilized the V-factor requirement of Haemophilus parainfluenzae as a basis for mutant isolation.
• Applied the developed procedure to generate mutants from Escherichia coli.
• Categorized wild-type and mutant E. coli strains into four distinct classes based on pyridine metabolism.

Main Results:

• Successfully isolated E. coli mutants with defects in NAD metabolism.
• Classified mutants into four groups: Class A (wild-type), Class B (altered internal NAD pools), Class C (excreting pyridine mononucleotides), and Class D (excreting NAD).
• Class B mutants showed a 10-fold variation in intracellular NAD concentration, while Class C and D mutants overproduced pyridine nucleotides by at least tenfold.

Conclusions:

• The developed procedure is effective for isolating NAD metabolism mutants.
• The identified mutant classes provide valuable tools for studying NAD biosynthesis and regulation.
• These mutants exhibit normal growth characteristics, facilitating further research into their metabolic functions.