Combination of Metabolomic and Proteomic Analysis Revealed Different Features among Lactobacillus delbrueckii Subspecies bulgaricus and lactis Strains While In Vivo Testing in the Model Organism Caenorhabditis elegans Highlighted Probiotic Properties

Abstract

<i>Lactobacillus delbrueckii</i> represents a technologically relevant member of lactic acid bacteria, since the two subspecies <i>bulgaricus</i> and <i>lactis</i> are widely associated with fermented dairy products. In the present work, we report the characterization of two commercial strains belonging to <i>L. delbrueckii</i> subspecies <i>bulgaricus</i>, <i>lactis</i> and a novel strain previously isolated from a traditional fermented fresh cheese. A phenomic approach was performed by combining metabolomic and proteomic analysis of the three strains, which were subsequently supplemented as food source to the model organism <i>Caenorhabditis elegans</i>, with the final aim to evaluate their possible probiotic effects. Restriction analysis of 16S ribosomal DNA revealed that the novel foodborne strain belonged to <i>L. delbrueckii</i> subspecies <i>lactis</i>. Proteomic and metabolomic approaches showed differences in folate, aminoacid and sugar metabolic pathways among the three strains. Moreover, evaluation of <i>C. elegans</i> lifespan, larval development, brood size, and bacterial colonization capacity demonstrated that <i>L. delbrueckii</i> subsp. <i>bulgaricus</i> diet exerted beneficial effects on nematodes. On the other hand, both <i>L. delbrueckii</i> subsp. <i>lactis</i> strains affected lifespan and larval development. We have characterized three strains belonging to <i>L. delbrueckii</i> subspecies <i>bulgaricus</i> and <i>lactis</i> highlighting their divergent origin. In particular, the two closely related isolates <i>L. delbrueckii</i> subspecies <i>lactis</i> display different galactose metabolic capabilities. Moreover, the <i>L. delbrueckii</i> subspecies <i>bulgaricus</i> strain demonstrated potential probiotic features. Combination of <i>omic</i> platforms coupled with <i>in vivo</i> screening in the simple model organism <i>C. elegans</i> is a powerful tool to characterize industrially relevant bacterial isolates.