Screening of Gaba production in members of the genus bifidobacterium

Abstract

Gamma-amino butyric acid (GABA) is the main inhibitor neurotransmitter in the central nervous system, regulates multiple physiological processes in the human body and its dysfunctions has been linked to anxiety and depression disorders. In recent years, dietary supplementation with GABA has been associated with antihypertensive, analgesic and antidepressant properties and thus there is an increasing interest in identifying probiotic strains with GABA production capabilities, which could act as delivery vectors of this neurotransmitter in the human gut. Several lactic acid bacteria, including lactobacilli and streptococcal strains, have been reported capable to produce GABA, though this activity has been scarcely explored in members of the genus Bifidobacterium. In this work the GABA production capability was studied among members of the genus Bifidobacterium. First, an in silico analysis was performed on available Bifidobacterium genomes, to determine how widespread GABA production genes are within this group of bacteria. Based on the results, a screening of GABA production capability was performed in a collection of 58 Bifidobacterium strain, mainly comprised of members of the species B. adolescentis. For this purpose, the strains were grown overnight in the presence of the GABA precursor, monosodium glutamate and then, GABA and residual monosodium glutamate concentrations were determined through high-performance liquid chromatography in cell-free supernatants. The presence of the gadB and gadC genes, encoding a glutamate decarboxylase and a glutamate/GABA antiporter system, respectively, in the GABA producing strains was determined through PCR. The gadB and gadC genes were commonly detected in strains belonging to the species B. adolescentis. Besides, 25 % of the analyzed strains were capable to transform almost all monosodium glutamate provided, to GABA. In conclusion, GABA production is a relatively common trait in B. adolescentis strains, which could represent potential candidates for GABA delivery in vivo.