[Phosphoenolpyruvate:hexose phosphotransferase systems in Lactobacillus species]

Area of Science:

• Microbiology
• Molecular Biology
• Biochemistry

Context:

• Phosphoenolpyruvate:hexose phosphotransferase systems (hexose-PTSs) are crucial for carbohydrate transport and metabolism in bacteria.
• Understanding the substrate specificity of these systems in different Lactobacillus species is essential for their industrial and probiotic applications.
• Lactobacillus casei and Lactobacillus acidophilus are important lactic acid bacteria with distinct metabolic capabilities.

Purpose:

• To investigate and compare the substrate range of hexose-PTSs in Lactobacillus casei subsp. casei LAC3 and Lactobacillus acidophilus LAC5.
• To characterize the nature (constitutive or inducible) of these PTS activities.
• To analyze the role of 2-deoxyglucose (2DG) in growth inhibition and to study 2DG-resistant mutants.

Summary:

• Lactobacillus casei LAC3 displayed constitutive PTS activity for glucose, mannose, glucosamine, 2-deoxyglucose, and fructose. Lactobacillus acidophilus LAC5 showed activity only for mannose and fructose.
• Both strains were inhibited by 2DG. Mutants DG329 (from LAC3) and DG504 (from LAC5) were isolated. DG329 showed defects in constitutive PTS activities and gained inducible activities for mannose and fructose.
• These findings suggest LAC3 possesses inducible PTSs for mannose/fructose alongside a constitutive Man-PTS, while LAC5 lacks the Man-PTS but has other constitutive mannose/fructose-specific PTSs.

Impact:

• Provides insights into the differential sugar metabolism pathways of Lactobacillus species.
• Identifies specific PTS systems in L. casei and L. acidophilus, potentially enabling targeted metabolic engineering.
• Contributes to understanding bacterial adaptation mechanisms to sugar analogs like 2DG.