title: Common Distribution ofgadOperon inLactobacillus brevisand its GadA Contributes to Efficient GABA Synthesis toward Cytosolic Near-Neutral pH.
abstract: Many strains of lactic acid bacteria (LAB) and bifidobacteria have exhibited strain-specific capacity to produce γ-aminobutyric acid (GABA) via their glutamic acid decarboxylase (GAD) system, which is one of amino acid-dependent acid resistance (AR) systems in bacteria. However, the linkage between bacterial AR and GABA production capacity has not been well established. Meanwhile, limited evidence has been provided to the global diversity of GABA-producing LAB and bifidobacteria, and their mechanisms of efficient GABA synthesis. In this study, genomic survey identified common distribution ofgadoperon-encoded GAD system inLactobacillus brevisfor its GABA production among varying species of LAB and bifidobacteria. Importantly, among four commonly distributed amino acid-dependent AR systems inLb. brevis, its GAD system was a major contributor to maintain cytosolic pH homeostasis by consuming protons via GABA synthesis. This highlights thatLb. brevisapplies GAD system as the main strategy against extracellular and intracellular acidification demonstrating its high capacity of GABA production. In addition, the abundant GadA retained its activity toward near-neutral pH (pH 5.5-6.5) of cytosolic acidity thus contributing to efficient GABA synthesis inLb. brevis. This is the first global report illustrating species-specific characteristic and mechanism of efficient GABA synthesis inLb. brevis.
authors.affiliation: School of Biological Sciences, The University of Hong Kong Hong Kong, Hong Kong.
authors.forename: Qinglong
authors.initials: Q
authors.lastname: Wu
authors.affiliation: Department of Animal Science, University of Manitoba Winnipeg, MB, Canada.
authors.forename: Hein Min
authors.initials: HM
authors.lastname: Tun
authors.affiliation: School of Biological Sciences, The University of Hong Kong Hong Kong, Hong Kong.
authors.forename: Yee-Song
authors.initials: YS
authors.lastname: Law
authors.affiliation: Department of Animal Science, University of ManitobaWinnipeg, MB, Canada; Department of Medical Microbiology, University of ManitobaWinnipeg, MB, Canada.
authors.forename: Ehsan
authors.initials: E
authors.lastname: Khafipour
authors.affiliation: School of Biological Sciences, The University of Hong KongHong Kong, Hong Kong; Victoria UniversityMelbourne, VIC, Australia.
authors.forename: Nagendra P
authors.initials: NP
authors.lastname: Shah
keywords: Lactobacillus brevis; acid resistance; genomic survey; glutamic acid decarboxylase; γ-aminobutyric acid (GABA)