AbiA, a lactococcal abortive infection mechanism functioning in Streptococcus thermophilus

Area of Science:

• Bacteriology
• Virology
• Molecular Biology

Background:

• Bacterial abortive infection (Abi) systems are crucial defense mechanisms against phage predation.
• Streptococcus thermophilus is a key starter culture in dairy fermentations, making phage resistance important.
• Understanding Abi mechanisms can enhance starter culture stability and industrial applications.

Purpose of the Study:

• To evaluate the efficacy of two lactococcal abortive infection (Abi) systems, AbiA and AbiG, against phages infecting Streptococcus thermophilus.
• To determine the influence of growth temperature on the effectiveness of these Abi mechanisms.

Main Methods:

• Genetic engineering of Streptococcus thermophilus 4035 to incorporate the AbiA and AbiG systems.
• Infection assays using a panel of phages targeting S. thermophilus.
• Testing phage sensitivity at different growth temperatures (30°C, 37°C, and 42°C).

Main Results:

• The AbiA system conferred resistance against six out of the tested phages at a growth temperature of 30°C.
• AbiA-mediated phage resistance was completely abolished at higher temperatures (37°C and 42°C).
• The AbiG system demonstrated no significant inhibitory effect on any of the tested S. thermophilus phages across all evaluated temperatures.

Conclusions:

• The AbiA system shows temperature-dependent efficacy in protecting Streptococcus thermophilus against specific phages.
• AbiG appears ineffective against the tested phage population in S. thermophilus under the study conditions.
• Optimizing temperature conditions is critical for the successful application of AbiA as a phage resistance strategy in S. thermophilus.