Characterization of a new virulent phage (MLC-A) of Lactobacillus paracasei

Area of Science:

• Microbiology
• Virology
• Food Science

Background:

• Probiotic dairy products rely on specific bacterial strains like Lactobacillus paracasei.
• Virulent bacteriophages pose a significant threat to industrial fermentation processes.
• Understanding phage-host interactions is crucial for maintaining culture stability.

Purpose of the Study:

• To isolate and characterize a novel virulent bacteriophage targeting Lactobacillus paracasei.
• To assess the phage's stability under processing conditions and its host range.
• To provide insights into phage sensitivity in probiotic cultures.

Main Methods:

• Isolation and electron microscopy of bacteriophage MLC-A.
• Determination of phage morphology and Siphoviridae family classification.
• Assessment of phage resistance to heat, chemicals, and optimal adsorption conditions.
• Host range determination and one-step growth kinetics analysis.
• Genome size estimation and restriction profiling.

Main Results:

• Bacteriophage MLC-A, belonging to the Siphoviridae family, was isolated from a probiotic dairy product.
• The phage exhibited resistance to pasteurization, alcohols, and sodium hypochlorite, but was inactivated by peracetic acid.
• Optimal adsorption occurred at 30°C, pH 5-7, with Ca2+ or Mg2+ ions.
• MLC-A infected L. paracasei and L. casei strains, with a latent period of 30 min and burst size of ~69 PFU/cell.
• Estimated genome size was ~37 kb, with a distinct restriction profile.

Conclusions:

• This study describes the first phage specific to L. paracasei isolated in Argentina.
• The isolation of MLC-A highlights the susceptibility of probiotic cultures to virulent phages.
• Findings are critical for managing phage contamination in dairy fermentation and probiotic production.