The host galaxies of radio-quiet quasars at 0.5<z<1.0

We present near-infrared H-band imaging of 15 intermediate redshift (0.5<z<1) radio quiet quasars (RQQ) in order to characterize the properties of their host galaxies. We are able to clearly detect the surrounding nebulosity in 12 objects, whereas the object remains unresolved in three cases. For all the resolved objects, we find that the host galaxy is well represented by a de Vaucouleurs r^{1/4} surface brightness law. This is the first reasonably sized sample of intermediate redshift RQQs studied in the near-infrared. The RQQ host galaxies are luminous (average M_H=-26.3+-0.6) and large giant elliptical galaxies (average bulge scale length R_e = 11.3\pm5.8 kpc). RQQ hosts are about 1 mag brighter than the typical low redshift galaxy luminosity L^*, and their sizes are similar to those of galaxies hosting lower redshift RQQs, indicating that there is no significant evolution at least up to z=1 of the host galaxy structure. We also find that RQQ hosts are about 0.5-1 mag fainter than radio-loud quasars (RLQ) hosts at the similar redshift range. The comparison of the host luminosity of intermediate redshift RQQ hosts with that for lower z sources shows a trend that is consistent with that expected from the passive evolution of the stars in the host galaxies. The nuclear luminosity and the nucleus/host galaxy luminosity ratio of the objects in our sample are intermediate between those of lower redshift RQQs and those of higher redshift (z>1) RQQs.Comment: A&A, accepted, 15 pages, 6 figures. Fig. 2 will only be published in the electronic version of A&

The luminous host galaxies of high redshift BL Lac objects

(abridged) We present near-infrared Ks-band imaging of 13 high redshift (0.6 < z < 1.3) BL Lac objects. We clearly detect the host in eight objects, and marginally in three others. In all cases, the host galaxy is well represented by an r^1/4 surface brightness law. The host galaxies of high redshift BL Lacs are large ( ~7 kpc) and very luminous ( = -27.9+-0.7), ~3 mag brighter than L*, and ~1 mag brighter than brightest cluster galaxies. They are also ~1 mag brighter than low redshift radio galaxies and appear to deviate from their K-z relationship. On the other hand, the high luminosities agree with the few optical studies of high redshift BL Lac hosts. The nuclear luminosity and the nucleus-galaxy luminosity ratio of the high redshift BL Lacs are much larger than those in low redshift BL Lacs. This may be due to either a higher intrinsic nuclear luminosity, or enhanced luminosity because of strong beaming. Contrary to what is observed in low redshift BL Lacs, the luminosities of the host galaxy and of the nucleus are fairly well correlated, as expected from the black hole mass - bulge luminosity relationship. High redshift BL Lacs radiate with a wide range of power with respect to their Eddington luminosity, and this power is intermediate between those in nearby BL Lacs and in luminous radio-loud quasars. The high redshift BL Lac host galaxies appear to be ~2 mag brighter than those at low redshift. This is likely due to a strong selection effect in the surveys of BL Lacs that makes observable only the most luminous sources at z > 0.5 and produces a correlation between the nuclear and the host luminosity. However, this may also suggest strong luminosity evolution which is inconsistent with a simple passive evolution of the host galaxies, and requires a contribution from relatively recent star formation episodes.Comment: A&A, accepted, 17 pages, 7 figures. The Appendix will only be published in the electronic version of A&

Characterization and genomic analysis of chromate resistant and reducing Bacillus cereus strain SJ1

<p>Abstract</p> <p>Background</p> <p>Chromium is a toxic heavy metal, which primarily exists in two inorganic forms, Cr(VI) and Cr(III). Chromate [Cr(VI)] is carcinogenic, mutational, and teratogenic due to its strong oxidizing nature. Biotransformation of Cr(VI) to less-toxic Cr(III) by chromate-resistant and reducing bacteria has offered an ecological and economical option for chromate detoxification and bioremediation. However, knowledge of the genetic determinants for chromate resistance and reduction has been limited so far. Our main aim was to investigate chromate resistance and reduction by <it>Bacillus cereus </it>SJ1, and to further study the underlying mechanisms at the molecular level using the obtained genome sequence.</p> <p>Results</p> <p><it>Bacillus cereus </it>SJ1 isolated from chromium-contaminated wastewater of a metal electroplating factory displayed high Cr(VI) resistance with a minimal inhibitory concentration (MIC) of 30 mM when induced with Cr(VI). A complete bacterial reduction of 1 mM Cr(VI) was achieved within 57 h. By genome sequence analysis, a putative chromate transport operon, <it>chrIA</it>1, and two additional <it>chrA </it>genes encoding putative chromate transporters that likely confer chromate resistance were identified. Furthermore, we also found an azoreductase gene <it>azoR </it>and four nitroreductase genes <it>nitR </it>possibly involved in chromate reduction. Using reverse transcription PCR (RT-PCR) technology, it was shown that expression of adjacent genes <it>chrA</it>1 and <it>chrI </it>was induced in response to Cr(VI) but expression of the other two chromate transporter genes <it>chrA</it>2 and <it>chrA</it>3 was constitutive. In contrast, chromate reduction was constitutive in both phenotypic and gene expression analyses. The presence of a resolvase gene upstream of <it>chrIA</it>1, an arsenic resistance operon and a gene encoding Tn7-like transposition proteins ABBCCCD downstream of <it>chrIA</it>1 in <it>B. cereus </it>SJ1 implied the possibility of recent horizontal gene transfer.</p> <p>Conclusion</p> <p>Our results indicate that expression of the chromate transporter gene <it>chrA</it>1 was inducible by Cr(VI) and most likely regulated by the putative transcriptional regulator ChrI. The bacterial Cr(VI)-resistant level was also inducible. The presence of an adjacent arsenic resistance gene cluster nearby the <it>chrIA</it>1 suggested that strong selective pressure by chromium and arsenic could cause bacterial horizontal gene transfer. Such events may favor the survival and increase the resistance level of <it>B. cereus </it>SJ1.</p

Cattle Mammary Bioreactor Generated by a Novel Procedure of Transgenic Cloning for Large-Scale Production of Functional Human Lactoferrin

Large-scale production of biopharmaceuticals by current bioreactor techniques is limited by low transgenic efficiency and low expression of foreign proteins. In general, a bacterial artificial chromosome (BAC) harboring most regulatory elements is capable of overcoming the limitations, but transferring BAC into donor cells is difficult. We describe here the use of cattle mammary bioreactor to produce functional recombinant human lactoferrin (rhLF) by a novel procedure of transgenic cloning, which employs microinjection to generate transgenic somatic cells as donor cells. Bovine fibroblast cells were co-microinjected for the first time with a 150-kb BAC carrying the human lactoferrin gene and a marker gene. The resulting transfection efficiency of up to 15.79×10−2 percent was notably higher than that of electroporation and lipofection. Following somatic cell nuclear transfer, we obtained two transgenic cows that secreted rhLF at high levels, 2.5 g/l and 3.4 g/l, respectively. The rhLF had a similar pattern of glycosylation and proteolytic susceptibility as the natural human counterpart. Biochemical analysis revealed that the iron-binding and releasing properties of rhLF were identical to that of native hLF. Importantly, an antibacterial experiment further demonstrated that rhLF was functional. Our results indicate that co-microinjection with a BAC and a marker gene into donor cells for somatic cell cloning indeed improves transgenic efficiency. Moreover, the cattle mammary bioreactors generated with this novel procedure produce functional rhLF on an industrial scale