Levansucrase from Halomonas smyrnensis AAD6T: first halophilic GH-J clan enzyme recombinantly expressed, purified, and characterized

Abstract The present study was aimed to characterize the chromate reducing ability of cells and cell-free extract (CFE) of Halomonas smyrnensis KS802 (GenBank Accession No. KU982965) and evaluate their effectiveness in tannery effluents. Viable cells of the strain reduced 200 µM Cr(VI) in basal medium for halophiles (MH) in 10 h and was inversely proportional to Cr(VI) concentrations. The rapid reduction by cells (10⁹ cells/mL) was achieved with 7.5% NaCl, at pH 7 and 37°C which increased with increasing cell density (10¹° cells/mL). While acetate, Cu³⁺, Fe³⁺, SO₄²⁻, and CO₃²⁻ were stimulating the reduction, the inhibitors retarded the process significantly. The NADH-dependent chromate reduction of the CFE was found to be constitutive with Km and Vmax values of 56.58 µM and 3.37 µM/min/mg protein respectively. The optimal reductase activity of the CFE was evident at 200 µM Cr(VI), 10% NaCl, pH 8.0 and at 45°C. A higher concentration of CFE and electron donors increased the enzyme activity but was impacted negatively by toxic metals and anions. Both the cells and CFE were capable of reducing Cr(VI) remarkably from tannery effluent. FTIR and XRD spectra of chromate reducing cells confirmed possible complexation of reduced Cr-species with functional groups on cell surface.

Download Full-text

Biomineralization of Monohydrocalcite Induced by the Halophile Halomonas smyrnensis WMS‐3

Minerals ◽

10.3390/min9100632 ◽

2019 ◽

Vol 9 (10) ◽

pp. 632 ◽

Cited By ~ 9

Author(s):

Pan ◽

Zhao ◽

Tucker ◽

Zhou ◽

Jiang ◽

...

Keyword(s):

Electron Microscopy ◽

Transmission Electron Microscopy ◽

Carbon Isotope ◽

Extracellular Polymeric Substances ◽

Salt Lake ◽

Stable Carbon Isotope ◽

Ion Concentration ◽

Molar Ratios ◽

Transmission Electron ◽

Halomonas Smyrnensis

The halophilic bacterium Halomonas smyrnensis from a modern salt lake used in experiments to induce biomineralization has resulted in the precipitation of monohydrocalcite and other carbonate minerals. In this study, a Halomonas smyrnensis WMS‐3 (GenBank:MH425323) strain was identified based on 16S rDNA homology comparison, and then cultured in mediums with 3% NaCl concentration to induce monohydrocalcite at different Mg/Ca molar ratios of 0, 2, 5, 7, and 9. The growth curve of WMS‐3 bacteria, pH values, NH4+ concentration, HCO3− and CO32− concentration, carbonic anhydrase (CA) activity, and the changes in Ca2+ and Mg2+ ion concentration were determined to further explore the extracellular biomineralization mechanism. Moreover, the nucleation mechanism of monohydrocalcite on extracellular polymeric substances (EPS) was analyzed through studying ultrathin slices of the WMS‐3 strain by High resolution transmission electron microscopy (HRTEM), Selected area election diffraction (SAED), Scanning transmission electron microscopy (STEM), and elemental mapping, besides this, amino acids in the EPS were also analyzed. The results show that pH increased to about 9.0 under the influence of ammonia and CA activity. The precipitation ratio (%, the ratio of the mass/volume concentration) of the Ca2+ ion was 64.32%, 62.20%, 60.22%, 59.57%, and 54.42% at Mg/Ca molar ratios of 0, 2, 5, 7, and 9, respectively, on the 21st day of the experiments, and 6.69%, 7.10%, 7.74%, 8.09% for the Mg2+ ion concentration at Mg/Ca molar ratios 2, 5, 7, and 9, respectively. The obtained minerals were calcite, Mg‐rich calcite, aragonite, and hydromagnesite, in addition to the monohydrocalcite, as identified by X-ray diffraction (XRD) analyses. Monohydrocalcite had higher crystallinity when the Mg/Ca ratio increased from 7 to 9; thus, the stability of monohydrocalcite increased, also proven by the thermogravimetry (TG), derivative thermogravimetry (DTG) and differential scanning calorimetry (DSC) analyses. The C=O and C–O–C organic functional groups present in/on the minerals analyzed by Fourier transform infrared spectroscopy (FTIR), the various morphologies and the existence of P and S determined by scanning electron microscope-energy dispersive spectrometer (SEM‐EDS), the relatively more negative stable carbon isotope values (−16.91‰ to −17.91‰) analyzed by a carbon isotope laser spectrometer, plus the typical surface chemistry by XPS, all support the biogenesis of these mineral precipitates. Moreover, Ca2+ ions were able to enter the bacterial cell to induce intracellular biomineralization. This study is useful to understand the mechanism of biomineralization further and may provide theoretical reference concerning the formation of monohydrocalcite in nature.

Download Full-text

Whole genome sequencing, assembly and annotation of Halomonas smyrnensis, a levan producing halophilic bacterium

EMBnet journal ◽

10.14806/ej.18.a.429 ◽

2012 ◽

Vol 18 (A) ◽

pp. 89 ◽

Cited By ~ 1

Author(s):

E Sogutcu ◽

Z Emrence ◽

M Arikan ◽

A Cakiris ◽

N Abaci ◽

...

Keyword(s):

Whole Genome Sequencing ◽

Genome Sequencing ◽

Halophilic Bacterium ◽

Whole Genome ◽

Halomonas Smyrnensis

Download Full-text

Halomonas smyrnensis sp. nov., a moderately halophilic, exopolysaccharide-producing bacterium

INTERNATIONAL JOURNAL OF SYSTEMATIC AND EVOLUTIONARY MICROBIOLOGY ◽

10.1099/ijs.0.037036-0 ◽

2013 ◽

Vol 63 (Pt_1) ◽

pp. 10-18 ◽

Cited By ~ 50

Author(s):

Annarita Poli ◽

Barbara Nicolaus ◽

Aziz Akın Denizci ◽

Bahar Yavuzturk ◽

Dilek Kazan

Keyword(s):

Type Species ◽

Rrna Gene ◽

Content Type ◽

Mean Values ◽

Moderately Halophilic ◽

Link Type ◽

Halomonas Elongata ◽

Nacl Concentration ◽

Wildlife Reserve ◽

Halomonas Smyrnensis

Four Gram-negative, moderately halophilic, exopolysaccharide-producing strains, designated AAD6T, AAD4, AAD17 and AAD21, were isolated from Çamaltı Saltern Area, a wildlife reserve in Sasalı, İzmir province located in the Aegean Region of Turkey. The isolates grew at an optimum NaCl concentration of 10 % (w/v). The major cellular fatty acids were C16 : 0, C18 : 1ω7c, C16 : 1ω7c and C12 : 0 3OH, respectively and the predominant lipoquinone was ubiquinone Q-9. The G+C content of the genomic DNA of strains AAD6T, AAD4, AAD17 and AAD21 was 63.0, 63.3, 62.8 and 62.6 mol%, respectively. Comparative 16S rRNA gene sequence studies showed that the isolates belonged to the genus Halomonas . The DNA–DNA hybridization mean values between the representative strain AAD6T and the closely related species Halomonas salina DSM 5928T, Halomonas halophila DSM 4770T, Halomonas maura DSM 13445T, Halomonas organivorans DSM 16226T, Halomonas elongata DSM 2581T, Halomonas koreensis JCM 12237T and Halomonas nitroreducens LMG 24185, were 40.8, 39.6, 24.2, 23.3, 12.6, 14.5 and 12.2 %, respectively. Based on these data the strains represent a novel species of the genus Halomonas for which the name Halomonas smyrnensis sp. nov. is proposed. The type strain is AAD6T ( = DSM 21644T = JCM 15723T).

Download Full-text