TY - JOUR A1 - Kraegeloh, A. A1 - Amendt, B. A1 - Kunte, Hans-Jörg T1 - Potassium Transport in a Halophilic Member of the Bacteria Domain: Identification and Characterization of the K+ Uptake Systems TrkH and TrkI from Halomonas elongata DSM 2581T N2 - The halophilic bacterium Halomonas elongata accumulates K+, glutamate, and the compatible solute ectoine as osmoprotectants. By functional complementation of Escherichia coli mutants defective in K+ uptake, we cloned three genes that are required for K+ uptake in H. elongata. Two adjacent genes, named trkA (1,374 bp) and trkH (1,449 bp), were identified on an 8.5-kb DNA fragment, while a third gene, called trkI (1,479 bp), located at a different site in the H. elongata chromosome, was found on a second 8.5-kb fragment. The potential protein expressed by trkA is similar to the cytoplasmic NAD+/NADH binding protein TrkA from E. coli, which is required for the activity of the Trk K+ uptake system. The deduced amino acid sequences of trkH and trkI showed significant identity to the transmembrane protein of Trk transporters. K+ transport experiments with trkH and trkI mutants of H. elongata revealed that TrkI exhibits a Km value of 1.12 mM, while the TrkH system has a half-saturation constant of 3.36 mM. Strain KB12, relying on TrkH alone, accumulated K+ with a lower Vmax and required a higher K+ concentration for growth in highly saline medium than the wild type. Strain KB15, expressing only TrkI, showed the same phenotype and the same K+ transport kinetics as the wild type, proving that TrkI is the main K+ transport system in H. elongata. In the absence of both transporters TrkH and TrkI, K+ accumulation was not detectable. K+ transport was also abolished in a trkA deletion mutant, indicating that TrkI and TrkH depend on one type of TrkA protein. Reverse transcriptase PCR experiments and Northern hybridization analyses of the trkAH locus revealed cotranscription of trkAH as well as a monocistronic transcript with only trkA. KW - Potassium transport KW - Osmoregulation KW - Halophilic Bacteria KW - Halomonas elongata KW - TrkH KW - TrkA PY - 2005 U6 - https://doi.org/10.1128/JB.187.3.1036-1043.2005 SN - 0021-9193 SN - 1098-5530 VL - 187 IS - 3 SP - 1036 EP - 1043 PB - American Society for Microbiology CY - Washington, DC AN - OPUS4-6294 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - GEN A1 - Kunte, Hans-Jörg ED - Gunde-Cimerman, N. ED - Oren, A. ED - Plemenitas, A. T1 - K+ Transport and its Role for Osmoregulation in a Halophilic Member of the Bacteria Domain: Characterization of the K+ Uptake Systems from Halomonas elongata KW - Osmoregulation KW - Potassium KW - Glutamate KW - Potassium transport KW - TrkH KW - TrkA KW - Trkl KW - Halomonas elongata KW - Halophilic Bacteria PY - 2005 SN - 1-402-03632-9 N1 - Serientitel: Cellular Origin, Life in Extreme Habitats and Astrobiology – Series title: Cellular Origin, Life in Extreme Habitats and Astrobiology IS - 9 SP - 289 EP - 300 PB - Springer CY - Berlin AN - OPUS4-11668 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Moghaddam, J. A. A1 - Boehringer, N. A1 - Burdziak, A. A1 - Kunte, Hans-Jörg A1 - Galinski, E. A. A1 - Schäberle, T. F. T1 - Different strategies of osmoadaptation in the closely related marine myxobacteria Enhygromyxa salina SWB007 and Plesiocystis pacifica SIR-1 N2 - Only a few myxobacteria are known to date that are classified as marine, owing to their salt dependency. In this study, the salt tolerance mechanism of these bacteria was investigated. To this end, a growth medium was designed in which the mutated Escherichia coli strain BKA13 served as sole food source for the predatory, heterotrophic myxobacteria. This enabled measurement of the osmolytes without any background and revealed that the closely related strains Enhygromyxa salina SWB007 and Plesiocystis pacifica SIR-1 developed different strategies to handle salt stress. Ple. pacifica SIR-1, which was grown between 1 and 4% NaCl, relies solely on the accumulation of amino acids, while Enh. salina SWB007, which was grown between 0.5 and 3% NaCl, employs, besides betaine, hydroxyectoine as the major compatible solute. In accordance with this analysis, only in the latter strain was a locus identified that codes for genes corresponding to the biosynthesis of betaine, ectoine and hydroxyectoine. KW - Osmoregulation KW - Myxobacteria KW - Betaine KW - Ectoine PY - 2016 U6 - https://doi.org/10.1099/mic.0.000250 VL - 162 IS - 4 SP - 651 EP - 661 AN - OPUS4-39115 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -