Integration of DNA into bacterial chromosomes from plasmids without a counter-selection marker.

Most bacteria can only be transformed with circular plasmids, so robust DNA integration methods for these rely upon selection of single-crossover clones followed by counter-selection of double-crossover clones. To overcome the limited availability of heterologous counter-selection markers, here we explore novel DNA integration strategies that do not employ them, and instead exploit (i) activation or inactivation of genes leading to a selectable phenotype, and (ii) asymmetrical regions of homology to control the order of recombination events. We focus here on the industrial biofuel-producing bacterium Clostridium acetobutylicum, which previously lacked robust integration tools, but the approach we have developed is broadly applicable. Large sequences can be delivered in a series of steps, as we demonstrate by inserting the chromosome of phage lambda (minus a region apparently unstable in Escherichia coli in our cloning context) into the chromosome of C. acetobutylicum in three steps. This work should open the way to reliable integration of DNA including large synthetic constructs in diverse microorganisms. © 2011 The Author(s)

Health status of hostel dwellers: Part IV. Immunisation of children

The immunisation status of children (0 - 5 years) living in the Zones, an urban migrant council-built hostel in Langa, was investigated to examine the effect of migrant labour and related to this, the effect of circular or oscillating migration between Cape Town and the eastern Cape (Transkei/Ciskei) on access to this preventive health care measure. 'Road-toHealth' cards were available for 69,4% of subjects - 78,8% for those born in Cape Town and 50,8% for those born in Transkei. Immunisation Of 'Road-to-Health' card holders ranged from 71,8% to 95%. The range dropped to 41 - 79,1% if it was assumed that children without 'Road-to-Health' cards (i.e. without positive proof of immunisation) had not been immunised. Children born in Cape Town have a significantly higher immunisation coverage than children born elsewhere (Transkei accounted for 82,7% of these children). Immunisations administered in Cape Town numbered 80,6%, while 62,6% of subjects were born in Cape Town. In Transkei, payment is required for immunisation, in Cape Town it is free. By implication, cost appeared to be an important reason for low coverage in Transkei. The findings of this study suggested that hostel migrant children who had access to the Cape Town health services through working parents had better immunisation coverage than children at the home-base who seldom or never reached the city

Harnessing open-source technology for low-cost automation in synthesis: flow chemical deprotection of silyl ethers using a homemade autosampling system.

An inexpensive homemade 3-axis autosampler was used to facilitate the automation of an acid catalysed flow chemical desilylation reaction. Harnessing open-source software technologies (Python, OpenCV), an automated computer-vision controlled liquid-liquid extraction step was used to provide effective inline purification. A Raspberry Pi single-board computer was employed to interface with the motors used in the autosampler and actuated fluidic valves

A survey of the physical health status of pupils aged 10 - 14 years in Standards 3 - 5 at three schools in New Crossroads, near Cape Town in the Western Cape

No Abstract

Galaxy Morphology from NICMOS Parallel Imaging

We present high resolution NICMOS images of random fields obtained in parallel to other HST observations. We present galaxy number counts reaching H=24. The H-band galaxy counts show good agreement with the deepest I- and K-band counts obtained from ground-based data. We present the distribution of galaxies with morphological type to H<23. We find relatively fewer irregular galaxies compared to an I-band sample from the Hubble Deep Field, which we attribute to their blue color, rather than to morphological K-corrections. We conclude that the irregulars are intrinsically faint blue galaxies at z<1.Comment: 13 pages, including 4 figures. Accepted for publication in ApJ Letter

Combinatorial metabolic engineering platform enabling stable overproduction of lycopene from carbon dioxide by cyanobacteria

Cyanobacteria are simple, efficient, genetically-tractable photosynthetic microorganisms representing ideal biocatalysts for CO2 capture and conversion, in principle. In practice, genetic instability and low productivity are key, linked problems in engineered cyanobacteria. We took a massively parallel approach, generating and characterising libraries of synthetic promoters and RBSs for the cyanobacterium Synechocystis, and assembling a sparse combinatorial library of millions of metabolic pathway-encoding construct variants. Laboratory evolution suppressed variants causing metabolic burden in Synechocystis, leading to expected genetic instability. Surprisingly however, in a single combinatorial round without iterative optimisation, 80% of variants chosen at random overproduced the valuable terpenoid lycopene from atmospheric CO2 over many generations, apparently overcoming the trade-off between stability and productivity. This first large-scale parallel metabolic engineering of cyanobacteria provides a new platform for development of genetically stable cyanobacterial biocatalysts for sustainable light-driven production of valuable products directly from CO2, avoiding fossil carbon or competition with food production

On The Age Estimation of LBDS 53W091

The recent spectral analysis of LBDS 53W091 by Spinrad and his collaborators has suggested that this red galaxy at z=1.55 is at least 3.5 Gyr old. This imposes an important constraint on cosmology, suggesting that this galaxy formed at z > 6.5, assuming recent estimates of cosmological parameters. We have performed chi^2 tests to the continuum of this galaxy using its UV spectrum and photometric data (RJHK). We have used the updated Yi models that are based on the Yale tracks. We find it extremely difficult to reproduce such large age estimates, under the assumption of the most probable input parameters. Using the same configuration as in Spinrad et al. (solar abundance models), our analysis suggests an age of approximately 1.4 -- 1.8 Gyr. The discrepancy between Spinrad et al.'s age estimate (based on the 1997 Jimenez models) and ours originates from the large difference in the model integrated spectrum: the Jimenez models are much bluer than the Yi models and the Bruzual \& Charlot (BC) models. Preliminary tests favor the Yi and BC models. The updated age estimate of LBDS 53W091 would suggest that this galaxy formed approximately at z=2-3.Comment: LaTeX, 18 eps files Accepted for publication in ApJ (Feb 10, 2000, vol 530), uses emulateapj.st