Microorganisms that are exposed to pollutants in the environment, such as metals/metalloids, have a remarkable ability to fight the metal stress by various mechanisms. These metal-microbe interactions have already found an important role in biotechnological applications. It is only recently that microorganisms have been explored as potential biofactories for synthesis of metal/metalloid nanoparticles. Biosynthesis of selenium (Se0) nanospheres in aerobic conditions by a bacterial strain isolated from the coalmine soil is reported in the present study.
Results
The strain CM100B, identified as Bacillus cereus by morphological, biochemical and 16S rRNA gene sequencing [GenBank:GU551935.1] was studied for its ability to generate selenium nanoparticles (SNs) by transformation of toxic selenite (SeO32-) anions into red elemental selenium (Se0) under aerobic conditions. Also, the ability of the strain to tolerate high levels of toxic selenite ions was studied by challenging the microbe with different concentrations of sodium selenite (0.5 mM-10 mM). ESEM, AFM and SEM studies revealed the spherical Se0 nanospheres adhering to bacterial biomass as well as present as free particles. The TEM microscopy showed the accumulation of spherical nanostructures as intracellular and extracellular deposits. The deposits were identified as element selenium by EDX analysis. This is also indicated by the red coloration of the culture broth that starts within 2-3 h of exposure to selenite oxyions. Selenium nanoparticles (SNs) were further characterized by UV-Visible spectroscopy, TEM and zeta potential measurement. The size of nanospheres was in the range of 150-200 nm with high negative charge of -46.86 mV.
Conclusions
This bacterial isolate has the potential to be used as a bionanofactory for the synthesis of stable, nearly monodisperse Se0 nanoparticles as well as for detoxification of the toxic selenite anions in the environment. A hypothetical mechanism for the biogenesis of selenium nanoparticles (SNs) involving membrane associated reductase enzyme(s) that reduces selenite (SeO32-) to Se0 through electron shuttle enzymatic metal reduction process has been proposed. 相似文献
From more than 500 tumours reported in human primary immune deficiencies a majority has been observed in two disorders: ataxia telangiectasia (A-T) and common variable immune deficiency (CVID). Since both diseases have an increased risk of lymphomas/leukaemias and gastrointestinal tumours, suggesting a common risk factor, and the cells derived from A-T patients exhibit an increased chromosomal radiosensitivity we analysed chromosome damage in the G2 lymphocytes of 24 CVID pateints and 21 controls after X-irradiation in vitro.
There was a significant difference in mean aberration yields between patients and controls. Three CVID patients had yields higher than the mean + 3SD of the controls. Six patients but only one control had yields higher than the mean + 2SD of controls. The patient with the highest chromosomal radiosensitivity subsequently developed a lymphoma. Repeat assays on the same blood sample, with a 24-h delay in setting up the second culture, showed as much variability for control donors as the variation between control donors although for CVID patients inter-individual variation was greater than the difference between results of repeat samples. There was a weak positive correlation between radiosensitivity and age of donor. Chromosomal radiosensitivity of five patients with X-linked hypogammaglobulinaemia was not different from healthy donors.
The mean mitotic index (MI) for unirradiated samples from CVID patients was significantly lower than for controls and there was an inverse relationship between MI and aberration yields in the patients, but not in controls. We suggest that the defect in CVID patients that reduces response to mitogenic stimuli may have mechanism(s) in common with those involved in cellular repair processes. 相似文献
Genera of the Cephennomicrus group of the Cephenniini (Scydmaenitae) are revised, and the following new taxa are described: Trichokrater gen.n. , Trichokrater ekkentros sp.n. (type species of Trichokrater) (Borneo), Cephennococcus gen.n. , Cephennococcus kuchingensis sp.n. (type species of Cephennococcus) (Borneo), Cephennococcus kenyirensis sp.n. (West Malaysia), Cephennococcus crassus sp.n. (Borneo), Cephennococcus minutissimus sp.n. (West Malaysia), Pomphopsilla gen.n. , Pomphopsilla luhya sp.n. (type species of Pomphopsilla) (Kenya) and Pomphopsilla soror sp.n. (Kenya). Unique subcuticular pockets with setose openings on the pronotum of Trurlia and Trichokrater are identified as glandular structures. Enigmatic internal prothoracic cavities are described for the first time in Scydmaeninae (in Cephennococcus, Pomphopsilla and a female of an undescribed genus from Sulawesi); their fine structure and function remain unknown. Parsimony‐based cladistic analysis of the adult morphology of genera of Cephenniini provided robust evidence for a monophyly of the Cephennomicrus group, composed of Cephennomicrus, Cephennula, Lathomicrus, Pomphopsilla, Cephennococcus, Trurlia, Trichokrater and two undescribed Oriental genera known from females only; this distinct and well‐supported lineage is a sister group of Cephennodes + Hlavaciellus. The genus Cephennomicrus represented in the analysis by species belonging to three previously postulated species groups is not monophyletic, and a comprehensive study comprising more taxa is necessary to reclassify this heterogeneous group. 相似文献
To evaluate breastfed infants' responses to scented objects, we videotaped
the facial and bodily reactions of sixty-three infants as they explored, in
succession, three toys that were identical in appearance but different in
their characteristic odor. Two of the toys were scented with odorants
previously shown to be transmitted to human milk, one with ethanol and the
other with vanilla, whereas the third toy was unscented. Each videotape was
subjected to frame-by-frame analysis to measure a variety of behaviors that
are considered either to be exploratory in nature in that they lead to
perceptual information about the object or to reflect the infants' hedonic
reaction. Analyses of these behaviors revealed that the infants looked more
and vocalized less in the presence of the vanilla-scented toy and spent
less time manipulating the ethanol-scented toy when compared with the
unscented toy. Moreover, differential exposure to the odors of ethanol and
vanilla, as indicated by differential consumption of alcohol by a parent or
use of vanilla-scented product by the mother, was related to differential
responses to these odors. These findings suggest that human infants are
able to detect and retain information about the chemical features of their
environment.
相似文献
Genera of Eutheiini are reviewed and Eutheimorphus is removed from this tribe of ant‐like stone beetles (Scydmaeninae) and transferred to Cephenniini. A monogeneric Marcepaniini trib.n. is described to accommodate Marcepania gen.n. from Malaysia, with five species: M. semengohensis sp.n. (the type species of Marcepania), M. tuberculata sp.n. , M. seramaensis sp.n. , M. minutissima sp.n. and M. elongata sp.n. A phylogenetic analysis of all genera of Cephenniini, Eutheiini and Marcepaniini based on adult morphological characters resulted in recovering a well‐supported monophyletic clade Eutheiini + (Marcepaniini + Cephenniini) and these tribes are included in Cephenniitae stat.n. (Eutheiini and Cephenniini are therefore removed from Scydmaenitae). Only a weak support for monophyly of Eutheiini was found, but morphological characters allow for maintaining this presumably relic group as a separate tribe. Previously proposed monophyletic groups within Cephenniini were recovered as such, but after inclusion of Eutheimorphus, a sister taxon to the ‘Cephennomicrus group’, the latter lineage gained weak statistical support. The evolutionary history of Cephenniitae is discussed, with focus on known northern hemisphere fossils classified in Scydmaenitae and Hapsomelitae, but possibly closely allied to Cephenniitae. Establishing the supertribe Cephenniitae is the first step toward a profound reclassification of Scydmaeninae on a robust phylogenetic basis. This published work has been registered in ZooBank, http://zoobank.org/urn:lsid:zoobank.org:pub:B0E1B12D-9587-4C4F-A908-A12A0C424A8C . 相似文献