{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,19]],"date-time":"2026-10-19T01:46:13Z","timestamp":1792374373107,"version":"4.4.0"},"reference-count":49,"publisher":"Frontiers Media SA","license":[{"start":{"date-parts":[[2021,9,10]],"date-time":"2021-09-10T00:00:00Z","timestamp":1631232000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100012166","name":"National Key Research and Development Program of China","doi-asserted-by":"publisher","award":["2017YFD0400300"],"award-info":[{"award-number":["2017YFD0400300"]}],"id":[{"id":"10.13039\/501100012166","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100001809","name":"National Natural Science Foundation of China","doi-asserted-by":"publisher","award":["31871767"],"award-info":[{"award-number":["31871767"]}],"id":[{"id":"10.13039\/501100001809","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":["frontiersin.org"],"crossmark-restriction":true},"short-container-title":["Front. Microbiol."],"abstract":"<jats:p><jats:italic>Enterococcus avium<\/jats:italic> (<jats:italic>E. avium<\/jats:italic>) is a common bacterium inhabiting the intestines of humans and other animals. Most strains of this species can produce gamma-aminobutyric acid (GABA) <jats:italic>via<\/jats:italic> the glutamate decarboxylase (GAD) system, but the presence and genetic organization of their GAD systems are poorly characterized. In this study, our bioinformatics analyses showed that the GAD system in <jats:italic>E. avium<\/jats:italic> strains was generally encoded by three <jats:italic>gadB<\/jats:italic> genes (<jats:italic>gadB1<\/jats:italic>, <jats:italic>gadB2<\/jats:italic>, and <jats:italic>gadB3<\/jats:italic>), together with an antiporter gene (<jats:italic>gadC<\/jats:italic>) and regulator gene (<jats:italic>gadR<\/jats:italic>), and these genes are organized in a cluster. This finding contrasts with that for other lactic acid bacteria. <jats:italic>E. avium<\/jats:italic> SDMCC050406, a GABA producer isolated from human feces, was employed to investigate the contribution of the three <jats:italic>gadB<\/jats:italic> genes to GABA biosynthesis. The results showed that the relative expression level of <jats:italic>gadB3<\/jats:italic> was higher than those of <jats:italic>gadB1<\/jats:italic> and <jats:italic>gadB2<\/jats:italic> in the exponential growth and stationary phases, and this was accompanied by the synchronous transcription of <jats:italic>gadC<\/jats:italic>. After heterologous expression of the three <jats:italic>gadB<\/jats:italic> genes in <jats:italic>Escherichia coli<\/jats:italic> BL21 (DE3), the <jats:italic>K<\/jats:italic><jats:sub>m<\/jats:sub> value of the purified GAD3 was 4.26 \u00b1 0.48 mM, a value lower than those of the purified GAD1 and GAD2. Moreover, <jats:italic>gadB3<\/jats:italic> gene inactivation caused decreased GABA production, accompanied by a reduction in resistance to acid stress. These results indicated that <jats:italic>gadB3<\/jats:italic> plays a crucial role in GABA biosynthesis and this property endowed the strain with acid tolerance. Our findings provided insights into how <jats:italic>E. avium<\/jats:italic> strains survive the acidic environments of fermented foods and throughout transit through the stomach and gut while maintaining cell viability.<\/jats:p>","DOI":"10.3389\/fmicb.2021.691968","type":"journal-article","created":{"date-parts":[[2021,9,10]],"date-time":"2021-09-10T05:14:24Z","timestamp":1631250864000},"update-policy":"https:\/\/doi.org\/10.3389\/crossmark-policy","source":"Crossref","is-referenced-by-count":12,"title":["Molecular Analysis of Glutamate Decarboxylases in Enterococcus avium"],"prefix":"10.3389","volume":"12","author":[{"given":"Xinyi","family":"Gu","sequence":"first","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Jiancun","family":"Zhao","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Rongling","family":"Zhang","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Ruohan","family":"Yu","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Tingting","family":"Guo","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Jian","family":"Kong","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1965","published-online":{"date-parts":[[2021,9,10]]},"reference":[{"key":"B1","doi-asserted-by":"publisher","first-page":"527","DOI":"10.3389\/fmicb.2019.00527","article-title":"GABA-producing natural dairy Isolate From artisanal zlatar cheese attenuates gut inflammation and strengthens gut epithelial barrier in vitro.","volume":"10","author":"Bajic","year":"2019","journal-title":"Front. 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