Morphological and physiological study of autolytic-defective Streptococcus faecium strains

Area of Science:

• Microbiology
• Molecular Biology
• Biochemistry

Background:

• Cell wall biosynthesis and turnover are critical for bacterial viability.
• Autolysis, the self-degradation of bacterial cells, is mediated by autolytic enzymes.
• Understanding autolysis is important for developing new antimicrobial strategies.

Purpose of the Study:

• To isolate and characterize autolytic-defective mutants of Streptococcus faecium.
• To investigate the physiological and biochemical properties of these mutants.
• To elucidate the role of autolytic enzymes in bacterial cell wall metabolism and survival.

Main Methods:

• Isolation of autolytic-defective mutants using selection strategies.
• Growth rate determination in various media.
• Assessment of cellular autolysis under different conditions (antibiotics, detergents, nutrient limitation).
• Quantification of autolytic enzyme levels (active and latent forms).
• Measurement of lipoteichoic acid and lipid content.

Main Results:

• Three autolytic-defective mutants of S. faecium were isolated.
• Mutants displayed slower growth rates, particularly in chemically defined media.
• Decreased rates of cellular autolysis and enhanced survival against cell wall synthesis-blocking antibiotics were observed.
• Reduced total autolytic enzyme levels and an increased ratio of latent to active forms were found.
• Elevated levels of cellular lipoteichoic acid and lipids were detected in the mutants.

Conclusions:

• Autolytic defects in S. faecium lead to altered growth characteristics and increased resistance to certain antibiotics.
• The regulation of autolytic enzyme activity and the composition of cell wall components are interconnected.
• These findings provide insights into bacterial cell wall dynamics and potential targets for therapeutic intervention.