Isolation and characterisation of moderately halophilic bacteriumHalomonas ventosae DL7 synthesizing ectoine as compatible solute

Annals of Microbiology (Impact Factor: 0.99). 09/2007; 57(3):401-406. DOI: 10.1007/BF03175080


A moderately halophilic Gram-negative bacterium, strain DL7, was isolated from saltern sediment of Dalian, China. Phylogenetic
analysis based on 16S rRNA gene sequences indicated that this isolate belongs to the genusHalomonas. Based on the taxonomic and DNA sequence in addition to high DNA-DNA homologies, we concluded that this strain was similar
with the type strain ofHalomonas ventosae. Ectoine, one of the representative compatible solutes, was mainly detected in the cells as a result of1H- and13C-NMR measurements when grown in the presence of wide concentration ranges of NaCl. The results showed that higher amount
of ectoine was synthesized in a shorter incubation time compared with those of other strains reported earlier.

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    ABSTRACT: Salinivibrio costicola subsp. yaniae (NCCB 100212) is a moderately halophilic bacterium which has recently been isolated in a saltern located on the coast of Yellow Sea of North China. S. costicola subsp. yaniae, which is termed as strain DL6, has a short generation time, i.e., doubling time was 11.4 min during 2.5-5.5 h of incubation. Glycine betaine, ectoine, and glutamate were identified as the predominant compatible solutes by <sup>13</sup>C-NMR analyses when strain DL6 was grown in the nutrient AS medium. Glycine betaine might be taken up or converted from choline rather than de novo synthesis, while ectoine was synthesized de novo. Under low salinity condition, on the other hand, glycine betaine has no effect on the growth of strain DL6, but it will improve the level of cells to cope with osmotic stress at high salinity. Glutamate did not support the cell survival for high osmotic stress. Therefore, strain DL6 developed and constructed such complex system to adapt itself against high salinity environments.
    OCEANS 2008 - MTS/IEEE Kobe Techno-Ocean; 05/2008
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    ABSTRACT: Halomonas ventosae DL7 is a moderately halophilic bacterium that can grow over a wide range of salinity, 1-23 % NaCl. In response to the external osmotic stress (1-3 M NaCl), strain DL7 can accumulate ectoine and hydroxyectoine as compatible solutes, both of which were identified by nuclear magnetic resonance (NMR) spectroscopy. Hydroxyectoine, derivative of ectoine, was synthesized as minor compound (10.1 mg/L) when incubated in nutrient medium at 30degC. However, the concentration of hydroxyectoine significantly increased with the increase of incubation temperature, the amount of which reached 81.8 mg /L at 42degC. Hydroxyectoine was converted from ectoine by hydroxylase and its gene fragments have been obtained by PCR amplification. In the mutant Escherichia coli strain which harbors the ectD gene, hydroxylase has been successfully expressed at 42degC, in which conversion from ectoine to hydroxyectoine was observed, but not as high as expected. These data suggest that hydroxyectoine was synthesized by complex reactions in H. ventosae DL7 to cope with the alteration of external environments.
    OCEANS 2008 - MTS/IEEE Kobe Techno-Ocean; 05/2008
  • [Show abstract] [Hide abstract]
    ABSTRACT: Salinivibrio costicola subsp. yaniae is a moderately halophilic bacterium which can grow over a wide range of salinity. In response to external osmotic stress (1-3 M NaCl), S. costicola subsp. yaniae can accumulate ectoine, glycine betaine, and glutamate as compatible solutes. We used suicide plasmids pSUP101 to introduce transposon Tn1732 into S. costicola subsp. yaniae via Escherichia coli SM10 mediated by conjugation. One Tn1732-induced mutant, MU1, which was very sensitive to the external salt concentration, was isolated. Mutant MU1 did not grow above 1.5 M NaCl and did not synthesize ectoine, but accumulated Ngamma-acetyldiaminobutyrate, an ectoine precursor, as confirmed by (1)H-NMR analysis. From these data, we concluded that ectoine performs a key role in osmotic adaptation towards high salinity environments in strain S. costicola subsp. yaniae.
    Bioscience Biotechnology and Biochemistry 09/2008; 72(8):1977-82. DOI:10.1271/bbb.70652 · 1.06 Impact Factor
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