Isolation and characterization of two protease-producing mutants from Staphylococcus aureus

Area of Science:

• Microbiology
• Molecular Biology

Background:

• Staphylococcus aureus produces low levels of extracellular proteases.
• Protease production is inducible by casein or skim milk powder.

Purpose of the Study:

• To isolate and characterize mutants of Staphylococcus aureus with increased protease production.
• To investigate the relationship between protease production and other metabolic functions, such as carbohydrate utilization.

Main Methods:

• Nitrosoguanidine mutagenesis of Staphylococcus aureus 8325N.
• Phenotypic characterization of mutants, including protease production, enzyme activity (deoxyribonuclease, alkaline phosphatase), and carbohydrate utilization.
• Analysis of reversion frequency and parental pattern recovery.

Main Results:

• Two mutants with significantly increased extracellular protease production were identified.
• Mutants exhibited altered patterns of extracellular deoxyribonuclease and alkaline phosphatase.
• Mutants were unable to utilize lactose, galactose, and mannitol, but could utilize glucose, indicating a potential uptake defect.
• High spontaneous reversion frequency to wild-type phenotype for carbohydrate utilization was observed, with revertants regaining the parental pattern.

Conclusions:

• A single genetic locus may be responsible for controlling both extracellular enzyme excretion and carbohydrate uptake in Staphylococcus aureus.
• The identified mutants provide valuable tools for studying the regulation of virulence factors and metabolic pathways in S. aureus.