Formation And Stabilization Of Selenium Nanoparticles In Comamonas Testosteroni S44 And Identification Of A Novel Species Of Domibacillus

Elemental selenium nanoparticles?SeNPs?are useful in medicine,environmental remediation and in material science.Many microorganisms are able to reduce selenium oxyanions to SeNPs?BioSeNPs?.BioSeNPssynthesized by bacteria are eco-friendly,cheaper,,more stable and less cytotoxic in comparison with chemically synthesized ones.Stability is one of the most important factors limiting the application of nanomaterials.However,the mechanisms affecting BioSeNPs formation and stability were still not fully understood.The main purpose of this study is to explore the factors affecting the formation and stabilization of BioSeNPs,and to guide artificial synthesis of stable SeNPs and application of SeNPs.The strain Comamonas testosteroni S44 was able to reduce selenite to BioSeNPs in cells..The chemical characters showed a maximum absorption peak of BioSeNPs was at572 nm,and the size range of most BioSeNPs was 100-300 nm.The zeta potential of BioSeNPs was negative 31.4�3 mV.BioSeNPs were coated in a thick layer of organic substrates observed by transmission electron microscopy?TEM?.Futhermore,Fourier transform infrared?FT-IR?and quantitative detection of the coating agents showed that one gram of purified BioSeNPs bound 1069 mg proteins,23 mg carbohydrates and only very limited amounts of lipids,indicating proteins play a major role on formation and stabilization of BioSeNPs.SDS-PAGE and proteomics of BioSeNPs showed more than800 proteins bound to BioSeNPs,and no specific assembly proteins were found.We further compared the components of higher abundant proteins between BioSeNPs and cellular fractions.The result showed proteins enriched in charged amino acids?Asp?Glu?Arg and Lys?are the major factor thought to govern the formation process and stabilization of BioSeNPs in bacteria.These findings are helpful for the artificial green synthesis of stable SeNPs under specific condition and guiding the surface modification of SeNPs in medicine,environment remediation and material science.The second part is to identify a novel of species of Domabacillus named XD80^T.The16S rRNA gene sequences analysis indicated that strain XD80^T was closely related to Domibacillus iocasae CCTCC AB 2015183^T?98.66%sequence similarity?,D.robiginosus DSM 25058^T?97.83%?,D.tundrae KCTC 33549^T?97.70%?and D.enclensis CCTCC AB 2011121^T?97.21%?.DNA-DNA relatedness between strain XD80^T and these strains were 37.4%,53.8%,53.6%and 52.7%?<70%?,respectively.Polyphasic taxonomy results showed strain XD80^T was a gram-reaction-positive,strictly aerobic,capsule-forming,motile,and rod-shaped bacterium.Strain XD80 grew at temperature range 4-42�C?optimal temperature is 28�C?.Growth occurred with NaCl concentrations in the range of 0-6.5%?optimum,2.5%?and pH 6.0-10.0?optimum,pH7.0?.The major polar lipids were diphosphatidylglycerol,phosphatidylglycerol,aminophospholipid and two unknown phospholipids.The predominant fatty acids??5%?were iso-C_15:0?37.3%?,anteiso-C_15:0?10.8%?,C_16:0?10.4%?,iso-C_17:0?10.3%?,C_16:1?11c?9.6%?and anteiso-C_17:0?7.4%?.MK-6?86.4%?was the major respiratory quinone.The cell-wall peptidoglycan contained meso-diaminopimelic acid?type A1??.Ribose and glucose were the major whole-cell sugars.The DNA G+C content was 46.4mol%.These polyphasic results indicated that strain XD80^T represents a novel species of the genus Domibacillus,for which the name Domibacillus antri sp.nov.is proposed.The type strain is XD80^T?=CCTCC AB 2015053^T=KCTC 33636^T?.This research enriched and improved the classification of genus Domibacillus,which laid a foundation for future use of the strain.