An Altered aroA Gene Product Confers Resistance to the Herbicide Glyphosate

The hypothesis that the herbicide glyphosate (N-phosphonomethylglycine) acts on plants and microorganisms by inhibiting synthesis of 5-enolpyruvyl-3-phosphoshikimate, a precursor to aromatic amino acids, was tested. Salmonella typhimurium was treated with ethyl methanesulfonate, and mutants mapping at the aroA locus, which encodes 5-enolpyruvyl-3-phosphoshikimate synthetase, were isolated by selection for glyphosate resistance. One of the mutants results in the synthesis of a 5-enolpyruvyl-3-phosphoshikimate synthetase that is resistant to inhibition by glyphosate. The mutant aroA gene and the corresponding wild-type allele were cloned. The mutation confers high resistance to glyphosate when introduced in Escherichia coli in the presence or absence of the wild-type aroA allele.     

Structural characterization of lignin in the process of cooking of cornstalk with solid alkali and active oxygen

A novel, efficient, and environmentally friendly technology is used in cornstalk cooking, active oxygen (O? and H?O?) cooking with solid alkali (MgO). After the cooking, the milled wood lignin in the raw material and pulp and the water-soluble and insoluble lignin in the yellow liquor were all characterized by attenuated total reflectance Fourier transform infrared spectroscopy and two-dimensional heteronuclear single-quantum coherence NMR. The results showed that the cooking procedure with solid alkali and active oxygen had a high selectivity for delignification, which could remove 85.5% of the lignin from the raw material. The syringyl (S/S'/S') units could be dissolved preferentially because of their high reactivity, and a novel guaiacyl unit with a carbonyl group (G') was generated in the cooking process. Moreover, during the cooking, the β-O-4' (A/A'/A″) structures as the main side-chain linkages in all the lignins could be partly broken and the β-O-4' (A') with a ring-conjugated structure was readily attacked by oxygen, whereas the H unit and β-5' and β-β' structures were found to stay stable without characteristic reaction.     

The thermostable β-1,3-1,4-glucanase from Clostridium thermocellum improves the nutritive value of highly viscous barley-based diets for broilers

1. Microbial β-1,3-1,4-glucanases improve the nutritive value of barley-based diets for poultry by effectively decreasing the degree of polymerisation of the anti-nutritive soluble β-glucans. Glycoside hydrolases (GHs) acting on recalcitrant polysaccharides display a modular architecture comprising a catalytic domain linked to one or more non-catalytic Carbohydrate-Binding Modules (CBMs).

2. GHs and CBMs have been classified in different families based on primary structure similarity (see CAZy webpage at http://www.cazy.org). The role of CBMs is to anchor the appended GHs into their target substrates, therefore eliciting the efficient hydrolysis of structural carbohydrates.

3. Here we describe the biochemical properties of the family 16 GH from Clostridium thermocellum, termed CtGlc16A. CtGlc16A is a thermostable enzyme that specifically acts on β-1,3-1,4-glucans with a remarkable catalytic activity (38000?U/mg protein).

4. CtGlc16A, individually or fused to the family 11 β-glucan-binding domain of cellulase CtLic26A-Cel5E of C. thermocellum, was used to supplement a highly viscous barley-based diet for broilers.

5. The data showed that birds fed on diets supplemented with the recombinant enzymes displayed an improved performance when compared with birds given diets not supplemented with exogenous enzymes. However, inclusion of the non-catalytic CBMs had no influence on the capacity of CtGlc16A to reduce the anti-nutritive effects of soluble β-1,3-1,4-glucans.

6. The data suggest that at elevated dosage rates, CBMs might be unable to potentiate the catalytic activity of appended catalytic domains; this effect may only be revealed when feed enzymes are incorporated at low levels.     

Isotopic paleoceanography of the Caribbean and East pacific: role of panama uplift in late neogene time

Comparisons of carbon isotopic data on benthic foraminifera from Deep Sea Drilling Project sites 502 (western Caribbean) and 503 (eastern Pacific) indicate that the difference between the Atlantic and the Pacific in the per mil enrichment in carbon-13 of total dissolved carbon dioxide increased about 6 million years ago and again 3 million years ago, when the difference reached the modern level (1 per mil). Comparisons of planktonic foraminiferal oxygen isotopic data for the Caribbean and the Pacific suggest that the salinity of Caribbean surface waters began increasing 4 million years ago, possibly in response to shoaling of the Panama isthmus. These results suggest that modern circulation patterns in the Caribbean and eastern Pacific developed by 3 million years ago in concert with changing tectonic, climatic, and biogeographic patterns.     

Modeling bleaching of tomato derivatives at subzero temperatures

This work was addressed to obtain a predictive model of the rate of bleaching in tomato derivatives at subzero temperatures. To this aim, a tomato puree was freeze-dried and equilibrated at increasing solid fractions. The bleaching rate was assessed by measuring tomato color during storage for up to 18 months at temperatures from -30 to 0 degrees C. The temperature dependence of the tomato-bleaching rate was neither predictable using the Arrhenius equation nor simply related to tomato physical state. The lack of a clear Arrhenius relation was attributed to the occurrence of temperature-dependent phenomena, such as ice crystallization and oxygen solubility modifications, which strongly changed the local concentration of reactants. A modified Arrhenius equation predicting the tomato-bleaching rate in the entire temperature range was proposed. Tomato concentration, and hence its physical state, affected the temperature dependence of bleaching, modifying apparent activation energy and frequency factor of the modified Arrhenius equation. In light of these considerations, a mathematical model was set up and validated to accurately predict the tomato-bleaching rate on the basis of only its concentration and storage temperature.     

ALZHEIMER'S CONGRESS: Further Progress on a

An experimental vaccine that can reverse Alzheimer's-like symptoms in mice is holding up under continued testing. The treatment appears to improve mental functioning in mice, and despite earlier concerns, is well tolerated by a variety of experimental animals, and by humans as well. Excitement was palpable here at last week's World Alzheimer Congress 2000, but researchers caution against undue optimism given that safety trials in Alzheimer's patients are just beginning and there is currently no evidence that it will help people with the disease.     

Fatal epizootic equine herpesvirus 1 infections in new and unnatural hosts

In a zoological collection, four black bears (Ursus americanus) died from neurological disease within six months. Independently in a geographically different zoo, two Thomson's gazelles (Eudorcas thomsoni) and 18 guinea pigs (Cavia porcellus f. dom.) suffered from neurological disorders. In addition, guinea pigs showed abortions and stillbirths. All affected animals displayed a non suppurative meningoencephalitis with intranuclear inclusion bodies. Immunohistology demonstrated equine herpes virus antigen and ultrastructurally herpes viral particles were detected. Virus isolation and molecular analysis identified neurotropic equine herpesvirus (EHV) 1 strains in both epizootics. There is serological evidence of a possible virus transmission from other equids to the affected animals. Cross-species transmission of EHV-1 should be considered in the management of captive wild equids and ungulates, particularly with respect to fatal disease in irreplaceable species.     

Genotyping of porcine circovirus type 2 from a variety of clinical conditions in China

Genotypes of porcine circovirus type 2 (PCV2) in clinical tissue specimens collected from pigs of different region in China between 2001 and 2003 were analyzed by PCR and restriction fragment length polymorphism (RFLP) analysis of PCV2 genomic DNA encompassing the complete ORF2. The results showed that nine different genotypes (A-I) were identified and designated CHN-2A, CHN-2B, CHN-2C, CHN-2D, CHN-2E, CHN-2F, CHN-2G, CHN-2H and CHN-2I, respectively. Amongst the genotypes, 0.6% were CHN-2A (1/173), CHN-2B (1/173) and CHN-2C (1/173) RFLP profile; 2.3% were CHN-2F (4/173) and CHN-2G (4/173); 5.8% were CHN-2D (10/173); 8.6% were CHN-2E (15/173); 18.5% were CHN-2I (32/173) and 60.7% were CHN-2H (105/173). Therefore, our results suggest that CHN-2H is the dominant genotype of PCV2 prevailing in China. Sequence analysis revealed that ORF2 genes of different genotypic PCV2 exhibited the variation extent of 90.5-99.5% and 88-100% in nucleotide and amino acid respectively. The deduced amino acid sequences alignment of the capsid protein encoded by ORF2 of PCV2 presented that three major regions with greater heterogeneity existed at residues 57-90, 121-136 and 180-191 among nine genotypic PCV2. It was concluded that there exist variation in ORF2 genes of different genotypic PCV2 prevailing in China.     

Beaming light from a subwavelength aperture

Light usually diffracts in all directions when it emerges from a subwavelength aperture, which puts a lower limit on the size of features that can be used in photonics. This limitation can be overcome by creating a periodic texture on the exit side of a single aperture in a metal film. The transmitted light emerges from the aperture as a beam with a small angular divergence (approximately +/-3 degrees ) whose directionality can be controlled. This finding is especially surprising, considering that the radiating region is mainly confined to an area with lateral dimensions comparable to the wavelength of the light. The device occupies no more than one cubic micrometer and, when combined with enhanced transmission, suggests that a wide range of photonic applications is possible.