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. 2016 Sep 28:6:34054.
doi: 10.1038/srep34054.

Characterization and Potential Applications of a Selenium Nanoparticle Producing and Nitrate Reducing Bacterium Bacillus oryziterrae sp. nov

Peng Bao  1   2 , Ke-Qing Xiao  3 , Hui-Jiao Wang  4 , Hao Xu  4 , Peng-Peng Xu  5 , Yan Jia  6 , Max M Häggblom  7 , Yong-Guan Zhu  1   3
Affiliations

Characterization and Potential Applications of a Selenium Nanoparticle Producing and Nitrate Reducing Bacterium Bacillus oryziterrae sp. nov

Peng Bao et al. Sci Rep. .

Abstract

A novel nitrate- and selenite reducing bacterium strain ZYKT was isolated from a rice paddy soil in Dehong, Yunnan, China. Strain ZYKT is a facultative anaerobe and grows in up to 150, 000 ppm O2. The comparative genomics analysis of strain ZYKT implies that it shares more orthologues with B. subtilis subsp. subtilis NCIB 3610T (ANIm values, 85.4-86.7%) than with B. azotoformans NBRC 15712T (ANIm values, 84.4-84.7%), although B. azotoformans NBRC 15712T (96.3% 16S rRNA gene sequence similarity) is the closest Bacillus species according to 16S rRNA gene comparison. The major cellular fatty acids of strain ZYKT were iso-C14:0 (17.8%), iso-C15:0 (17.8%), and C16:0 (32.0%). The polar lipid profile consisted of phosphatidylethanolamine, diphosphatidylglycerol, phosphatidylglycerol and an unidentified aminophospholipid. Based on physiological, biochemical and genotypic properties, the strain was considered to represent a novel species of the genus Bacillus, for which the name Bacillus oryziterrae sp. nov. is proposed. The type strain is ZYKT (=DSM 26460T =CGMCC 1.5179T). Strain ZYKT can reduce nitrate to nitrite and ammonium and possesses metabolic genes for nitrate reduction including nar, nap and nrf. Biogenic selenium nanoparticles of strain ZYKT show a narrow size distribution and agree with the gaussian distribution. These selenium nanoparticles show significant dose-dependent inhibition of the lung cancer cell line H157, which suggests potential for application in cancer therapy.

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Figures

Figure 1
Figure 1
Selenite reduction (A) and nitrate reduction with nitrous oxide and ammonia generation (B) by strain ZYKT.
Figure 2
Figure 2. Operons encoding putative nitrate reductases of strain ZYKT.
Figure 3
Figure 3. Proposed model of terminal dissimilatory nitrate, nitrite and selenite reductions in strain ZYKT.
Proteins in blue block are encoded by the same operon. Uptake of molecule is represented by the direction of the arrows. Ovals: subunits of putative reductases; Circular: putative selenite reductase; Rectangles: putative transporters.
Figure 4
Figure 4
Representative SEM images of SeNPs from strain ZYKT (A), The scale is 0.5 μm. Energy dispersive X-ray spectroscopy (EDX) spectrum of the electron-dense SeNPs (B). Corresponding size distribution histograms (C). Dose-dependent inhibitions of SeNPs on the viability of cancer cell line H157 following 24 h exposure (D).
See this image and copyright information in PMC

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