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A Bacillus subtilis ΔpdxT mutant suppresses vitamin B6 limitation by acquiring mutations enhancing pdxS gene dosage and ammonium assimilation

  • Pyridoxal‐5’‐phosphate (PLP), the biologically active form of vitamin B6, serves as a cofactor for many enzymes. The Gram‐positive model bacterium Bacillus subtilis synthesizes PLP via the PdxST enzyme complex, consisting of the PdxT glutaminase and the PdxS PLP synthase subunits, respectively. PdxT converts glutamine to glutamate and ammonia of which the latter is channelled to PdxS. At high extracellular ammonium concentrations, the PdxS PLP synthase subunit does not depend on PdxT. Here, we assessed the potential of a B. subtilis ΔpdxT mutant to adapt to PLP limitation at the genome level. The majority of ΔpdxT suppressors had amplified a genomic region containing the pdxS gene. We also identified mutants having acquired as yet undescribed mutations in ammonium assimilation genes, indicating that the overproduction of PdxS and the NrgA ammonium transporter partially relieve vitamin B6 limitation in a ΔpdxT mutant when extracellular ammonium is scarce. Furthermore, we found that PdxS positively affects complex colony formation in B.Pyridoxal‐5’‐phosphate (PLP), the biologically active form of vitamin B6, serves as a cofactor for many enzymes. The Gram‐positive model bacterium Bacillus subtilis synthesizes PLP via the PdxST enzyme complex, consisting of the PdxT glutaminase and the PdxS PLP synthase subunits, respectively. PdxT converts glutamine to glutamate and ammonia of which the latter is channelled to PdxS. At high extracellular ammonium concentrations, the PdxS PLP synthase subunit does not depend on PdxT. Here, we assessed the potential of a B. subtilis ΔpdxT mutant to adapt to PLP limitation at the genome level. The majority of ΔpdxT suppressors had amplified a genomic region containing the pdxS gene. We also identified mutants having acquired as yet undescribed mutations in ammonium assimilation genes, indicating that the overproduction of PdxS and the NrgA ammonium transporter partially relieve vitamin B6 limitation in a ΔpdxT mutant when extracellular ammonium is scarce. Furthermore, we found that PdxS positively affects complex colony formation in B. subtilis. The catalytic mechanism of the PdxS PLP synthase subunit could be the reason for the limited evolution of the enzyme and why we could not identify a PdxS variant producing PLP independently of PdxT at low ammonium concentrations.show moreshow less

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Metadaten
Author: Björn Richts, Sabine Lentes, Anja PoehleinORCiD, Rolf DanielORCiD, Fabian M. CommichauORCiD
URL:https://sfamjournals.onlinelibrary.wiley.com/doi/abs/10.1111/1758-2229.12936
DOI:https://doi.org/10.1111/1758-2229.12936
ISSN:1758-2229
Title of the source (English):Environmental Microbiology Reports
Document Type:Scientific journal article peer-reviewed
Language:English
Year of publication:2021
Volume/Year:13
Issue number:2
First Page:218
Last Page:233
Faculty/Chair:Fakultät 2 Umwelt und Naturwissenschaften / FG Synthetische Mikrobiologie
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