title: Plant-derived compatible solutes proline betaine and betonicine confer enhanced osmotic and temperature stress tolerance to Bacillus subtilis.
abstract: L-Proline is a widely used compatible solute and is employed by Bacillus subtilis, through both synthesis and uptake, as an osmostress protectant. Here, we assessed the stress-protective potential of the plant-derived L-proline derivatives N-methyl-L-proline, L-proline betaine (stachydrine), trans-4-L-hydroxproline and trans-4-hydroxy-L-proline betaine (betonicine) for cells challenged by high salinity or extremes in growth temperature. l-Proline betaine and betonicine conferred salt stress protection, but trans-4-L-hydroxyproline and N-methyl-L-proline was unable to do so. Except for L-proline, none of these compounds served as a nutrient for B. subtilis. L-Proline betaine was a considerably better osmostress protectant than betonicine, and its import strongly reduced the l-proline pool produced by B. subtilis under osmotic stress conditions, whereas a supply of betonicine affected the L-proline pool only modestly. Both compounds downregulated the transcription of the osmotically inducible opuA operon, albeit to different extents. Mutant studies revealed that L-proline betaine was taken up via the ATP-binding cassette transporters OpuA and OpuC, and the betaine-choline-carnitine-transporter-type carrier OpuD; betonicine was imported only through OpuA and OpuC. L-Proline betaine and betonicine also served as temperature stress protectants. A striking difference between these chemically closely related compounds was observed: L-proline betaine was an excellent cold stress protectant, but did not provide heat stress protection, whereas the reverse was true for betonicine. Both compounds were primarily imported in temperature-challenged cells via the high-capacity OpuA transporter. We developed an in silico model for the OpuAC-betonicine complex based on the crystal structure of the OpuAC solute receptor complexed with L-proline betaine.
authors.affiliation: Max Planck Institute for Terrestrial Microbiology, Emeritus Group R. K. Thauer, Karl-von-Frisch Strasse 10, 35043 Marburg, Germany.|Al-Azhar University Gaza, Faculty of Science, Biology Department, PO Box 1277, Gaza, Palestine.|Laboratory for Microbiology, Department of Biology, Philipps University Marburg, Karl-von-Frisch Strasse 8, 35043 Marburg, Germany.
authors.forename: Abdallah
authors.initials: A
authors.lastname: Bashir
authors.affiliation: LOEWE Center for Synthetic Microbiology, Philipps University Marburg, Hans-Meerwein Strasse, 35043 Marburg, Germany.|Laboratory for Microbiology, Department of Biology, Philipps University Marburg, Karl-von-Frisch Strasse 8, 35043 Marburg, Germany.
authors.forename: Tamara
authors.initials: T
authors.lastname: Hoffmann
authors.affiliation: Laboratory for Microbiology, Department of Biology, Philipps University Marburg, Karl-von-Frisch Strasse 8, 35043 Marburg, Germany.
authors.forename: Bettina
authors.initials: B
authors.lastname: Kempf
authors.affiliation: NMR Facility, Department of Chemistry, Philipps University Marburg, Hans-Meerwein Strasse 8, 35043 Marburg, Germany.
authors.forename: Xiulan
authors.initials: X
authors.lastname: Xie
authors.affiliation: Institute of Biochemistry, Heinrich Heine University Düsseldorf, Universitätsstrasse 1, 40225 Düsseldorf, Germany.
authors.forename: Sander H J
authors.initials: SHJ
authors.lastname: Smits
authors.affiliation: LOEWE Center for Synthetic Microbiology, Philipps University Marburg, Hans-Meerwein Strasse, 35043 Marburg, Germany.|Laboratory for Microbiology, Department of Biology, Philipps University Marburg, Karl-von-Frisch Strasse 8, 35043 Marburg, Germany.
authors.forename: Erhard
authors.initials: E
authors.lastname: Bremer
mesh_terms: D001412:Bacillus subtilis / Q000187:drug effects / Q000502:physiology* / Q000528:radiation effects; D006358:Hot Temperature; D009997:Osmotic Pressure; D064209:Phytochemicals / Q000378:metabolism*; D010944:Plants / Q000737:chemistry*; D011392:Proline / Q000031:analogs & derivatives* / Q000378:metabolism; D013312:Stress, Physiological
chemical_list: D064209:Phytochemicals; D011392:Proline; C003342:stachydrine